Ahead of the dangerous season: what is important to know about West Nile fever. West Nile fever: routes of infection, symptoms and treatment How is West Nile fever transmitted

In 1937, research was carried out regarding Japanese encephalitis. It was then that there was an epidemic outbreak and for the first time West Nile fever was detected in a person’s blood. The disease is caused by a mosquito bite. In the article we will look at what this disease is, how it is dangerous for humans, and what preventive methods should be used.

How is West Nile fever diagnosed?

Diagnosis of this natural focal viral disease is quite problematic. In epidemic regions, any manifestation of influenza conditions observed in the summer and autumn can be mistaken for West Nile fever.

To avoid confusion with diagnosis, it is recommended that when making a diagnosis, rely strictly on the results of laboratory studies and tests. When outbreaks of the disease are observed in a region, based on clinical and epidemiological indications, the diagnosis is made with more reliable probability. For example:

• A person lives near focal outbreaks of the disease;
• He often goes out into nature and spends his holidays in places where there are a lot of mosquitoes near water bodies;
• The disease occurs after eating food contaminated with the virus;
• Using water collected from an open reservoir.

The causative agent of the disease can be isolated from blood fluid taken for testing. laboratory analysis. It can also be detected in a patient by taking cerebrospinal fluid for a test during an acute period of the disease, starting from the fifth day of the incubation period.

During this same period, fever can be detected using PCR. To carry out this analysis, a portion is taken from the patient cerebrospinal fluid or blood serum. The sample is taken strictly with a syringe, then the liquid is placed in a sterile tube.

All medical instruments must be used for one-time use using antiseptic agents. It is recommended to store samples in freezer at a temperature of -60-70 C in a solution of liquid nitrogen.

Classification of febrile conditions

Today, many methods are used to detect fever, the best one being ELISA. Using serological diagnostics, you can detect antibodies that are related to the IgM and IgG classes. The first type of strain is usually detected already 2-3 days after the onset of the disease; their titers become too active after 7-14 days.

To conduct it correctly serological diagnostics, two doses are taken from the patient at once:

• The first sample is taken when a person has been sick for about a week;
• A second sample of the necessary liquids is taken 14-21 days after the first analysis.

The patient is diagnosed only when the doctor compares the results of both laboratory tests, as there are similarities with Q fever.

Differential diagnosis of the disease

1. How is West Nile fever different from the flu?

This type of diagnosis can be carried out depending on the manifestations and clinical form of the disease. West Nile fever has its own differences from influenza manifestations. Let's look at them:

• There are no signs of laryngeal tracheitis;
• The duration of a febrile state usually does not exceed 4-5 days;
• The disease differs from ARVI in that in the upper respiratory tract there are no catarrhal manifestations;
• But when West Nile fever intensifies, intoxication of the body is pronounced;

1. Differences between West Nile fever and meningitis

• The disease differs from the enteroviral meningitis form in the duration of the febrile period;
• The patient experiences rapid intoxication due to pleocytosis;
• Laboratory testing of cerebrospinal fluid is quite slow;

1. How is West Nile fever different from herpes encephalitis?

This is the hardest thing of all diagnostic studies to detect fever in a person:

• If, against the background of a febrile state, a complication occurs in the form of herpetic encephalitis, then the patient may have a sudden seizure and then coma usually ensues. In this case, differentiated diagnosis is made based on the tests performed;
• To do this, a portion of cerebrospinal fluid and blood is taken from the patient, and then examined using immunological techniques. The patient also undergoes a tomogram and MRI of the brain.

1. Differences between West Nile fever and tuberculous meningitis

The difference between a febrile illness and meningitis developed in tuberculosis is that when the nerve endings are damaged in patients, the primary symptoms appear much earlier, on about 3-5 days.

After a mosquito bite, the pathogen enters the human circulatory system. Moving through the bloodstream, it enters the tissue lymph nodes. Through its actions, the viral infection affects capillary vessels, where it then replicates in the endothelium.

Due to the pathogenic effects of harmful microorganisms on the body, the following occurs:

• Damage to neurons, which is what causes the subsequent manifestation of neurological symptoms in the patient;
• Due to damage to the capillaries in the brain, edema and swelling of the soft membrane develops;
• Locally located manifestations related to hemorrhagic syndrome occur.

In all clinical forms, West Nile fever is accompanied by body heat up to 38-40 C. The duration of high temperature is either 1-2 days, or severe cases– up to 14-21 days.

Treatment of fever

If a patient’s temperature rises rapidly and exceeds 40 C, then mandatory hospitalization in a medical facility is required. Also, when observing general cerebral symptoms or there are manifestations of meningitis against the background of West Nile fever.

There is no effective treatment to kill the fever virus yet. Treatment is mainly aimed at eliminating symptoms, and immunomodulatory therapy (interferon Amexin) is also carried out. The basis of treatment is pathogenetic procedures syndromic. Let's consider what procedures medical therapy includes:

• Treatment is aimed at eliminating swelling of the soft membranes of the brain, which determine the severity of the disease, as well as the expected outcome;
• Conducted preventive measures, as well as treatment of all abnormalities and complications associated with external respiration;
• Treatment of complications observed in the functioning of the cardiovascular system;
• It is necessary to significantly reduce the manifestation of seizures and hyperthermic syndrome.

To relieve symptoms, many antiviral drugs have not given the expected results, so only symptomatic treatment is carried out:

1. If the patient has high cranial pressure, he is prescribed Furosemide, as well as potassium-containing drugs. Or Veroshpiron, since it is milder in action, and besides, it is a non-potassium-saving agent;
2. For swelling of the soft membrane of the brain, the patient is given Furosemide with Mannitol. With rapid progression of edema, Dexamethasone is also prescribed as an additional effect;
3. If there is a large loss of fluid from the body, it is necessary to administer liquid solutions in the form of a dropper. This can be a colloidal solution of Albumin or intravenous polyionic liquid Trisol. Dilute them with water in a ratio of 2:1;
4. In case of hypoxia, the patient observes frequent shortness of breath, generalized convulsions, hypocapnia or coma, inhalations with the addition of oxygen are prescribed;
5. To relieve the symptoms of a convulsive state, the patient takes Seduxen;
6. Antibacterial drugs are prescribed if the patient develops a secondary bacterial infection;
7. Vitamin complexes and microelements.

Patients with manifestations of encephalitis should be treated in the intensive care unit medical institution. When observing failures in respiratory system the patient is transferred to artificial ventilation.

Duration therapeutic therapy may be 7-10 days. If observed side effects from the nervous system, treatment may take about a month. After the end of the hospital stay, the patient is transferred under dispensary observation.

Consequences and complications

Many forms of this natural focal disease are most often either mild or medium degree gravity flow. The only exception here may be the meningoencephalitis form, in some cases it leads to death. Speedy recovery ends in a form similar to influenza, asymptomatic and meningeal.

After experiencing a fever, some complications and side effects are possible. Let's get acquainted with them:

• Muscle tremors that persist for some time;

• Paresis of the limbs, as well as the endings of the nerve roots;
• Chronic fatigue. By the way, it lasts even after the person has fully recovered.

Each of us may well encounter this viral disease, but this does not mean that after a mosquito bite, any of its forms may appear. Even if primary symptoms are observed, West Nile fever usually goes away without any particular consequences.

Symptoms of fever

From the time the pathogen enters the human body until the appearance of primary symptoms, one week usually passes, in some cases it can take up to three weeks. This time is the incubation period.

As soon as the concentration of pathogenic microorganisms increases to the maximum, they emerge from the donor organs, where they multiplied, and their primary replication occurred.

Clinical manifestations

When secondary bacteremia occurs, the primary symptoms of the disease begin to appear. Let's take a look at some of the main symptoms of fever:

• The onset of the disease is acute;
• A rapid increase in temperature to 38-40 C in just a few hours;
• Observation of general intoxication symptoms (gag reflex, nausea);
• Severe chills, general malaise;
• Localized soreness in the forehead, eyeballs;
• Palpable soreness of the muscle surface in the lumbar and cervical region;
• Arthralgia.

Further diagnosis of symptoms most often depends on the type of viral infection affecting. Although, usually when infected with West Nile fever, the pathogen first attacks important organs: the soft membrane of the brain, liver, kidneys.

Let's consider the most common symptoms when infected with this natural focal infection:

1. If infection occurs with a pathogen that was dominant in the 90s. last century, then the patient may initially experience conjunctivitis, body rashes, pharyngitis, vomiting symptoms, hepatolienal syndrome. “Old” strains are usually benign;
2. If a person enters the body with a more “modern” strain, then the development of the disease will follow a sadder scenario. Clinical symptoms have more variations, since everything here depends on multiple forms of fever;
3. Subclinical form of fever clinical manifestations does not have. The diagnosis here is made based on the results of a screening study, for example, if at least one of their titers is increased by 4-5 times, then this indicates the presence of a disease in the body;
4. With the influenza-like type of illness, people do not often visit doctors, so it is the least studied. Most often this form is taken as colds, since the primary symptoms are quite similar. Health deterioration occurs within 3-5 days. In this case, the patient develops meningitis symptoms, a rapid increase in body temperature, radicular pain, and tremor. This condition lasts about 10 days;
5. In terms of general brain symptoms, the meningitis form of the disease occupies a leading place. This also adds focal symptoms- nystagmus, pyramidal signs. Muscle tremors and lethargy are felt.

Description:

West Nile fever is an acute viral zooanthroponotic natural focal disease with a transmissible transmission mechanism, characterized by polyadenopathy, erythema and inflammation of the meningeal membranes, occurring against the background of a febrile intoxication syndrome.

The first epidemic outbreak was recorded in 1937 during a study of Japanese. In the middle of the 20th century, another epidemic outbreak was registered in Africa and Asia, later in the Mediterranean countries (especially Israel and Egypt), the southern part of Russia, Belarus, Ukraine, Romania, the Czech Republic and Italy. Subsequently it was carried out serological test, confirming the presence of antibodies to the virus - in the Krasnodar Territory, Omsk and Volgograd regions, in Belarus, Azerbaijan, Tajikistan and Ukraine - these studies raise the question of the endemicity of the territories and confirm the fact of transmission of the disease, even in an erased / subclinical form. The relevance of this disease increased in 1999-2003, when the incidence began to increase in the Astrakhan region, Volgograd and Krasnodar regions.

Causes of West Nile fever:

The causative agent of West Nile fever is a flavivirus of group B of the togavirus family, size - 20-30 nm, contains RNA, has a spherical shape. Keeps well frozen and dried. Dies at temperatures above 56°C for 30 minutes. Inactivated by ether and deoxycholate. Has hemagglutinating properties.

The carriers of the virus are mosquitoes, ixodid and argasid ticks, and the reservoir of infection is birds and rodents. West Nile fever has a distinct seasonality - late summer and autumn. Young people get sick more often.

The risk of the disease is higher in people over 50 years of age. Probability of occurrence serious symptoms The disease burden is higher in people over 50 years of age and they should be especially careful about mosquito bites.

Being outdoors puts you at risk. The more time you spend outdoors, the longer the length of time you are likely to be bitten by an infected mosquito. If you spend a lot of time outdoors for work or leisure, be careful not to be bitten by mosquitoes.

The risk of illness from a medical procedure is very low. Before use, all donated blood is tested for the presence of the WNV virus. The risk of contracting WNV through an organ transplant is very low, so people who need surgery should not refuse it because of this risk. If you have any concerns, talk to your doctor.

Pregnancy and breastfeeding do not increase the risk of contracting West Nile fever. Researchers have not yet reached a definitive conclusion as to what risk WNV poses to the fetus or infant, which becomes infected through mother's milk. If you are concerned, talk to your doctor or nurse.

Symptoms of West Nile fever:

Incubation period is the time from the beginning of the introduction of the pathogen to the first clinical symptoms and, in in this case it lasts 3-8 days on average, but can last up to 3 weeks. During this period, the pathogen travels its way from the moment of the mosquito bite, with the subsequent reproduction of the pathogen at the site of the bite, further developing bacteremia and primary replication in the vascular endothelium and organs of the SSF (the system of monocytic phagocytes - everything that belongs to these organs is described above).

As soon as the pathogen reaches a certain concentration and leaves these target organs, where the primary reproduction occurred, replication occurs, a secondary one occurs and this marks the beginning visible symptoms. The period of clinical manifestations - as soon as secondary bacteremia begins, there is an acute onset with a rise in temperature to 38.5-40 ° C and it increases within several hours, accompanied by general intoxication symptoms in the form of:, most often localized in the forehead, pain in the eyeballs, vomiting, generalized myalgia (muscle pain is especially noticeable in the neck and lower back), arthralgia (joint pain) and general malaise.

The patient's appearance resembles hemorrhagic fever - redness of the face, injection of scleral vessels, redness and granularity of the mucous membranes of the cheeks and hard palate. The further stage of symptoms will depend on the type of infecting strain (but in any case, the following target organs are most often affected: liver, brain, kidneys):

When affected by “old” strains (i.e. those that were common before the 90s), the following occurs: conjunctivitis, polyadenopathy, rash, hepatolienal syndrome, dyspeptic disorders. But with these strains the course is benign.

When infected with “new strains,” the further picture of development may turn out to be a little sadder, and at the same time, clinical manifestations are more variable and associated with various forms of this disease:

   - In the subclinical form there are no clinical manifestations, diagnosis is possible only with the help of a screening test - determination of IgM or an increase in the IgG titer by 4 or more times.
  
- The influenza-like form is the least studied, because people often do not go to the doctor due to nonspecific symptoms, citing a cold. But as soon as the general condition worsens, no one connects this with the previous symptoms. In this form, deterioration of the condition is recorded on days 3-5 and manifests itself in the form of increased headache, appearance and vomiting, tremor, dizziness, radicular pain, skin hyperesthesia, meningeal symptoms, prolonged fever - a consistently high temperature that lasts about 10 days. This symptom complex is more typical for new strains.

   - The meningeal form is characterized by the emergence of general cerebral symptoms in first place ( headache, lethargy that does not bring relief, muscular), this clinic is also accompanied by focal symptoms - anisoreflexia, pyramidal signs.

   - Meningoencephalic form is the most severe form of the disease, because cerebral symptoms are more pronounced with a gradual increase: confusion, agitation, stupor often turning into coma. Also last but not least are focal symptoms: paresis cranial nerves, nystagmus, paresis of the limbs, respiratory disorders, central disorders hemodynamics. With this form, mortality reaches 50%, and in those who have recovered, frequent complications in the form of paresis, muscle tremors and prolonged asthenia.

Diagnostics:

Diagnosis and differential diagnosis are based on clinical, epidemiological and laboratory data. The main clinical signs are: acute onset of the disease, a relatively short febrile period, serous, systemic damage to the mucous membranes, lymph nodes, organs of the reticuloendothelial system and the heart. Rarely, a rash may occur.

Epidemiological prerequisites may include staying in an area where West Nile fever is endemic - North and East Africa, the Mediterranean, the southern regions of our country, information about mosquito or tick bites in these regions.

General blood and urine tests, as a rule, do not reveal pathological changes. It can be observed that in 30% of patients the number of leukocytes is less than 4-109/l. In the cerebrospinal fluid - lymphocytic pleocytosis (100-200 cells), normal or slight increased content squirrel. Laboratory transcript provided serological reactions RTGA, RSK and RN by the method of paired sera. However, since many flaviviruses have a close antigenic relationship, the detection of antibodies to one of them in blood serum may be due to the circulation of another virus. The most reliable evidence of West Nile virus infection is detection of the pathogen. The virus is isolated from the patient's blood in MK-2 cell culture and in mice weighing 6-8 g (intracerebral infection). Identification of the pathogen is carried out by the direct method of fluorescent antibodies using species-specific luminescent immunoglobulin to West Nile virus.

Differential diagnosis should be carried out with other arbo viral infections, mycoplasmosis, ornithosis, listerellosis, toxoplasmosis, tuberculosis, rickettsiosis, syphilis, influenza and other acute respiratory diseases, enterovirus infection, acute lymphocytic choriomeningitis.

Treatment for West Nile fever:

Since all viral diseases are treated with viroid drugs, West Nile fever was no exception, but none of them antiviral drugs did not give the expected result and, on this moment Treatment is limited to symptom relief:

1) For high intracranial pressure - furosemide with potassium preparations or veroshpiron (it acts more slowly compared to furosemide, but is potassium-sparing).
2) For cerebral edema - mannitol followed by the administration of furosemide. If cerebral edema is rapidly progressive, dexamethasone is additionally prescribed.
3) Compensation of fluid volume - intravenous infusions of polyionic solutions (Trisol) are prescribed and colloidal solutions(albumin, rheopolyglucin) – 2:1
4) To combat hypoxia, oxygen inhalations are prescribed and transferred to mechanical ventilation for the following indications:

West Nile fever (WNF) first became known in the late 1930s, when researchers were able to isolate the causative agent of this disease from the blood of a patient. Subsequently, data began to appear on the widespread spread of this viral infection among the population of Asian countries, South America and Africa.

According to statistics, outbreaks of this disease are especially often observed in many Mediterranean countries (in particular in Egypt and Israel). also in medical literature cases of detection of this viral infection are described in Indonesia, India and France (in Corsica and the coast Mediterranean Sea). Scientists were able to identify foci of this disease in Pakistan, Senegal, Turkmenistan, Moldova, Zaire, Algeria, Nigeria, Azerbaijan, Armenia, Sudan, Tajikistan, Kazakhstan, Ethiopia, the Czech Republic, Romania, in the Omsk, Volgograd, Astrakhan, Odessa regions, etc. the expansion of the nosoarea occurred at the end of the last century. Researchers associate such a spread of the disease from regions with a particularly hot climate to areas with moderate weather conditions with seasonal migrations of wild birds, which are a reservoir of infection.

WN fever is a zooanthroponotic (that is, affecting both people and animals) viral infection, which is acute, transmitted transmissibly (during bites by blood-sucking arthropods) and is accompanied by the occurrence of:

• fever;
• systemic lesions of the mucous membranes;
• serous inflammation of the membranes of the brain (sometimes up to meningoencephalitis);
• lymphadenopathy;
• in rare (up to 5%) cases, the appearance of a skin rash.

Not only people, but also mammals can be infected. According to statistics, this disease is more often detected among people whose professions are related to agriculture, or rural residents. Also, an increased risk of infection is observed among hunters, fishermen and others who spend a lot of time in the favorite places of arthropods (for example, near water bodies).

As a rule, outbreaks of infection are observed in early spring or in the summer-autumn period. The peak incidence - more than 90% of all identified outbreaks - is recorded from July to October, when the number of blood-sucking insects reaches its maximum.

In the literature you can find other names for the viral disease discussed in this article:

• West Nile fever;
• MN encephalitis;
• duck fever.

In some cases, this infection can cause complications that are dangerous to health and life, such as cerebral edema, which can subsequently cause coma and death of the patient. Not only residents of endemic dangerous regions, but also tourists who are going to visit these geographical areas should know about it. You can get information about the causes, symptoms, methods of diagnosis and treatment of West Nile fever in this article.

Characteristics of the infectious agent and routes of its transmission

This pathology is viral in nature. The pathogen enters the human body through the bite of a blood-sucking insect.

The development of WN fever is provoked by the invasion of the body by an RNA-containing flavovirus of group B. It has a spherical shape and dimensions of 20-30 nm.

Natural susceptibility to infection with the WN fever virus is high, and after an infection, those who have recovered develop intense or persistent immunity.

How does the infection develop?

After entering the blood, the virus, along with its current, spreads throughout the body, causing systemic lesions:

• First of all it suffers lymphoid tissue and as a result, the patient exhibits lymphadenopathy.
• If the infectious agent penetrates the blood-brain barrier, then the infected person may develop damage to the substance and membranes of the brain (up to).

In some cases, infection leads to the death of the patient.

Symptoms

In some cases, after infection with the pathogen of WN fever, the patient does not develop any symptoms, but in others, after 3-14 days (sometimes after 3 weeks), the patient develops signs of this viral disease. According to statistics and WHO, asymptomatic of this disease is observed in 80% of cases, and the manifest form of ZN fever proceeds typically and with the development of violent symptoms.

In the manifest course, the disease manifests itself in two variants:

• without damage to the central nervous system – accompanied by flu-like symptoms (sometimes with the addition of neurotoxicosis);
• with damage to the central nervous system - accompanied by meningeal or meningoencephalitic manifestations.

When clinical symptoms occur, signs of infection usually occur acutely, and the viral infection manifests itself with an increase in temperature to high numbers (38-40 °C). The febrile period is accompanied by chills.

Often, before the onset of a fever, the following symptoms are felt:

• severe weakness;
• loss of appetite;
• a feeling of tension in the muscles (usually the calf muscles);
• headache.

The duration of the increase in temperature usually ranges from 5 to 7 days (sometimes 1-2 days). ZN fever is characterized by a remitting course of a febrile period with periodic chills and heavy sweating.

In addition to fever, patients show signs of intoxication:

• frequent and strong, localized in the area of ​​the eye sockets and forehead;
• myalgia (especially intense in the neck and lower back);
• pain in the eyes;
• mild arthralgia without swelling of the skin over the articular joint.

At the peak of the development of intoxication syndrome, the patient experiences the following symptoms:

• repeated vomiting;
• reluctance to eat;
• chest discomfort and heart pain;
• sensations of heart sinking;
• drowsiness.

The skin of patients becomes hyperemic, and about 5% of them develop small papular rashes. In rare cases, with a prolonged and undulating course of the febrile period, such elements of the rash can transform into hemorrhagic ones.

Almost all infected people experience redness of the conjunctiva and injection of the blood vessels of the eyeballs, and pain is felt when pressing on the eyes.

Many patients have enlarged lymph nodes. As a rule, the pathological process involves:

• submandibular;
• lateral cervical;
• Anglomaxillary;
• cubital;
• axillary lymph nodes.

When palpated, they are sensitive or slightly painful.

Sometimes infected people experience nasal congestion and a dry cough. When examining the oral cavity, granularity and redness of the mucous membranes of the hard and soft palate are revealed.

The following changes are detected in the heart and blood vessels:

• tendency to;
• muffled heart sounds;
• a rough systolic murmur heard at the apex of the heart (sometimes);
• on : focal disorders, manifestations of hypoxia of the heart muscle, slowing of atrioventricular conduction.

Upon examination, the doctor may identify the following symptoms:

• thick gray-white coating on the tongue;
• dry tongue;
• diffuse pain when palpating the anterior wall of the abdomen;
• moderate sensitivity and enlargement of organs determined by palpation of the spleen and liver;
• without painful sensations in a stomach.

When the pathogen penetrates the blood-brain barrier, which is observed in approximately 50% of cases, the patient, against the background of the above-described manifestations, develops following signs serous meningitis:

• increased tone of the neck muscles (that is, their rigidity);
• Kernig's sign;
• Brudzinski's symptoms;
• signs of inflammatory processes in the cerebrospinal fluid (lymphocytes up to 70-90%, pleocytosis up to 100-200 cells in 1 μl);
• horizontal nystagmus;
• asymmetry of the palpebral fissures (mild);
• decreased tendon reflexes;
• proboscis reflex;
• decreased muscle tone;
• lack of abdominal reflexes.

Encephalitic manifestations of MN fever are detected in very rare cases, but residual signs of asthenia of a mixed nature, manifested in weakness, increased sweating, memory impairment, sleep disturbances and mental depression, persist for a long time.

Flu-like form

The influenza-like form of the disease is characterized by fever, sore throat, sneezing and cough.

With this course of infection, signs of fever (for several days), weakness, eye pain and chills are detected. In some cases, patients complain of cough and discomfort (soreness, soreness) in the throat.

Upon examination, the following signs are determined:

• redness of the back of the pharynx and palatine arches;
• scleritis

In some cases, signs of indigestion may occur:

• diarrhea;
• nausea;
• vomit;
• stomach ache;
• and not always).

Typically, a flu-like course occurs as a viral infection and is often accompanied by signs of meningism.

Neuroinfectious form

This form of the disease is observed in most clinical cases. With this course of MN fever, the patient exhibits the following symptoms:

• temperature increased to 38-40 °C (for 7-10 days or several weeks), accompanied by chills;
• sweating;
• nausea and vomiting (up to 5 times a day), which is not associated with food intake;
• headache;
• lower back pain (not always);
• myalgia (not always).

In more rare cases, symptoms of meningism, serous meningitis, and in extremely rare cases, meningoencephalitis are observed. After the patients’ condition improves, they continue to have the following residual neurological manifestations for a long time:

• weakness;
• apathy;
• memory impairment;
• sleep disorders.

Exanthematous form

This form of infection is extremely rare. On days 2-4, the patient develops elements of maculopapular (less commonly roseola-like or scarlet-like) polymorphic exanthema. Against the background of these manifestations there is:

• feverish condition;
• catarrhal disorders;
• intoxication syndrome.

The rash disappears after a few days and no pigmentation remains on the skin after the rash. Often, with this form of MN fever, the patient's lymph nodes become enlarged. They can be moderately painful when trying to palpate or make movements.

Character of the current

According to specialists, this infection is asymptomatic in 80% of cases. Mild signs of infection by the virus occur in 20% of those infected. They usually have the following symptoms:

• headache;
• fever;
• vomit;
• nausea;
• enlarged lymph nodes;
• myalgia;
• rash on the chest, back and stomach.

As a rule, such manifestations of infection persist for several days.

Severe WN fever is extremely rare - out of about 150 infected people, only one person suffers a severe illness. Such infected people exhibit the following symptoms:

• high fever;
• stupor;
• headache;
• shiver;
• stiffness of the neck muscles;
• muscle weakness;
• convulsions;
• numbness;
• paralysis;
• loss of vision.

These signs of infection may last for several weeks. After this the patient long time manifestations of neurological consequences persist.

Possible complications

Consequences of MN fever occur in most cases only during the neuroinfectious course of the disease. With the development of meningoencephalitis, the following may develop:

• paralysis;
• paresis.

In rare cases, the infection leads to the death of the patient.

More often, the neuroinfectious course of this disease causes:

• swelling of brain tissue;
• violations cerebral circulation.

Diagnostics

PCR helps detect fragments of genetic material (DNA) of the causative virus in the blood or other biological media of a patient.

When making a diagnosis, the doctor takes into account clinical, epidemiological and laboratory data. The following signs may indicate infection:

• acute onset;
• relatively short duration of fever;
• systemic damage to mucous tissues, organs and lymph nodes;
• serous meningitis;
• stay in endemic dangerous regions and the fact of being bitten by a mosquito or tick.

To assess the patient's condition, the following studies are performed:

• – leukopenia;
• virological analysis to detect WN fever virus (on culture media or on laboratory mice);
• enzyme-linked immunosorbent assay (ELISA);
• lumbar puncture followed by collection of cerebrospinal fluid for analysis (it will reveal a slight increase in protein levels, pleocytosis).

To exclude erroneous diagnosis, it is carried out differential diagnosis with the following diseases:

• and other acute respiratory infections;
• acute lymphocytic choriomeningitis;
• listerellosis;
• tuberculosis;
• rickettsiosis.

Treatment

So far, scientists have not been able to develop drugs for the etiotropic treatment of MN fever. The patient is advised to remain in bed and take symptomatic medications.

The first serious talk about West Nile fever was in 1937, when the first serious epidemiological outbreak occurred. It's spicy viral disease characterized by erythema, polyadenopathy, and possible inflammation meningeal membranes. The causative agent of the disease is a flavivirus belonging to group B. You can become infected at any age, but people over fifty years of age are most susceptible to the disease. There are still no special antiviral drugs for West Nile fever, and all treatment comes down directly to the relief of obvious symptoms.

Causes and diagnosis of the disease

People's susceptibility to disease depends mainly on geographical location. For example, in more southern countries, such as Egypt, children are most often affected, and in more northern ones, adults are already affected. In our country, low-endemic areas include southern regions, such as Volgograd, Astrakhan, as well as Stavropol and Krasnodar region. West Nile fever has no gender restrictions, and the most active period of spread occurs in late summer and early autumn.

In Russia, this disease was first registered in 1999, but its serious surge occurred at the end of 2014 and the beginning of 2015. The Volgograd region, in which several dozen cases have already been identified, as well as a number of other southern regions, came under attack. It is predicted that in the coming years the disease will spread to some northern regions of the country.

West Nile virus circulation pattern

In most cases, the disease is transmitted through the bite of a mosquito vector or tick. Those, in turn, become infected through birds, animals or bats, which are the source of the disease. The likelihood of infection through any medical procedures extremely small. In addition, hospitals constantly monitor for the presence of this virus in donated blood or organs.

There are several methods for diagnosing this disease. First of all, those persons who are subject to research are those who for a long time stayed in certain endemic areas. If West Nile fever is suspected, a complete blood count or lumbar puncture is performed. Some serological diagnostic methods are also used. The genetic material of the main causative agent of the disease can be detected in the body using a genetic method that examines not only the blood, but also the cerebrospinal fluid.

Main symptoms of the disease

From the moment the pathogen enters the body until the first symptoms appear, as a rule, eight days pass, while in some individual cases this period can be extended to three weeks. In most cases, visible symptoms begin with a rise in body temperature to forty degrees, chills, pain in the head and eyes. Vomiting may begin, and the patient begins to feel a general malaise.

When in dangerous areas where there is a possibility of contracting West Nile fever, it is recommended to use repellent, as well as wear long clothing and a hat.

Symptoms of West Nile fever also include severe redness faces, development, granularity of mucous membranes. The patient may experience scleritis and pharyngitis, rash and dyspeptic disorders. This disease is also characterized by muscle pain, convulsions, dizziness and respiratory disorders. More severe forms of the disease can lead to coma.

Treatment and prevention of the disease

Since the disease is viral, its therapy is reduced to the use of viroid drugs. At the moment, it is only possible to relieve the symptoms of the disease. On average, the course of treatment is ten days; if complications are diagnosed, it can be extended to thirty days. After recovery, it is recommended to constantly monitor the doctor for a long period, up to full recovery ability to work.

Treatment and prevention regimen for West Nile fever

If the disease occurs with high intracranial pressure, the patient is prescribed furosimide, as well as drugs containing potassium. In case of cerebral edema, the use of mannitol or dexamethasone is recommended. Intravenous infusions of various polyionic solutions, such as Trisol or albumin, may also be prescribed. Very often, oxygen inhalations are included in the course of treatment.

If the patient experiences severe convulsions, the doctor prescribes the use of Relanium. To improve cerebral circulation, the use of pentoxypheline is recommended. In case of secondary infections, antibiotic therapy may be prescribed together with complex application vitamin preparations. During illness, it is advisable to follow a daily routine and eat a balanced diet.

Measures to prevent West Nile fever include reducing the number of mosquitoes and ticks. For this purpose, the relevant services carry out anti-mosquito treatment of the areas where these insects are found to breed. Basements of residential and administrative buildings are also treated. During the active season of the disease in dangerous areas, people should minimize their exposure to the open air, and also use clothing that can protect against mosquito bites.

West Nile fever is a viral disease caused by a pathogen belonging to the flavovirus family, transmitted through arthropod bites and causing the development of a febrile syndrome, rash, damage to the meninges with the development of sometimes quite severe neurological disorders. The first official mention of this infection was made public in 1937 in a state belonging to North Africa, in Uganda. Subsequently, similar episodes of infection began to be recorded in Asian countries. As a result of the development of tourism, West Nile fever is often registered in the countries of France, India, as well as in many countries that formerly belonged to the USSR. Thanks to ongoing research, it has been established that a person is highly susceptible to this infection, but after the disease acquires immunity against a certain type of virus transmitted.

West Nile virus

West Nile fever is caused by a virus that belongs to the genus Flavovirus, which contains a ribonucleic acid or RNA molecule. In diameter, its dimensions reach from 40 to 60 nanometers with a characteristic spherical shape. The surface of the virion is covered with a capsule, which provides its main protective properties, as well as with numerous spines. The composition of these spines includes a specific glycoprotein, which is capable of causing agglutination reactions of red blood cells in the human body, leading to their deposition on the walls of blood vessels. In addition, this virus contains a soluble antigen, which has tropism for such cells in the human body as histiocytes in connective tissue, alveolar macrophages, Kupffer cells in the liver, Langerhans cells, synovial membranes and osteoclasts bone tissue, macrophages bone marrow, lymph nodes, spleen.

When the West Nile virus infects the body, it primarily damages organs with these types of cells. One of the most important features The structure of this virus is its high genetic variability, which determines the constant diagnosis of different types of virus strains, which can sometimes have a severe course, often causing the death of the patient.

With regard to the physical properties of the pathogen, it has been established that it is unstable at room temperature and dies when heated to 56°C for 30 minutes. However, the virus tolerates freezing well and can survive at sub-zero temperatures, down to -70°C. Of all kinds chemical substances It is unstable and quickly dies when exposed to deoxycholate and ether.

An interesting pattern has been established in the registration of cases of the disease among the population of different ages: for example, in countries where West Nile fever is quite widespread, children most often get sick, but in the countries of the former Soviet Union, where, one might say, this infection spread as a result of its mass importation , adults get sick.

The source of infection is domestic and wild birds, ticks, mosquitoes, bats, and rodents. The mechanism of transmission of infection is considered to be transmissible, therefore, West Nile fever is caused in a person by the bite of a mosquito or tick infected with the virus. It was found that mosquitoes belonging to the genus Culex and Ixodidae, as well as Argasid ticks, are carriers of the disease. The disease is characterized by seasonality, which manifests itself from the beginning of summer until the onset of autumn, namely until October, when it gets colder and such conditions for the development of mosquitoes are unfavorable.

There are 2 types of virus circulation in nature:

- the urban cycle, which involves birds that live and live near humans, as well as mosquitoes belonging to the genus Culex, which feed on the blood of humans and these bird species;

- the rural cycle, which includes wild birds that settle in wetlands, as well as mosquitoes that feed on the blood of these birds, the so-called ornithophilous.

Despite numerous studies, the pathogenesis of West Nile fever remains not fully understood. It has been established that after being bitten by an infected mosquito healthy person, the virus penetrates his blood and spreads throughout his organs and tissues. If it penetrates the blood-brain barrier, it causes corresponding damage to the brain. However, cases of infection with an asymptomatic course have also been identified. Rarely, but cases of death after infection are still recorded. It is also considered possible for the virus to persist in the human body for 1 month or more. The fact of the effect of the virus on the fetus when a pregnant woman is infected, as well as in the case of West Nile fever in a nursing mother, remains unclear.

Symptoms and signs of West Nile fever

The incubation period for West Nile fever is approximately 3 to 6 days, but can sometimes be up to 3 weeks. Quite often before the manifestation of the main clinical signs, typical for this infection, patients begin to worry about weakness, body and muscle aches, and headaches, which are often combined in the so-called prodromal period. Next comes an abrupt increase in temperature to 38-39°C and above, which lasts on average about a week, but sometimes can bother the patient for only 1-2 days. During the day, a decrease in temperature is accompanied by profuse sweating, giving way again to chills and an increasing rise in temperature. At the same time, the person is bothered by a very persistent, severe pain in the eyeballs, in the muscles of the whole body, often even in the joints, although upon examination no damage to the joints in the form of effusions is recorded. Vomiting without relief is also often observed up to several times during the day, and discomfort in the left half of the chest.

Upon careful examination of the patient, hyperemia of the skin can be noted with the frequent detection of a maculopapular rash, however, variants of the course of the disease with a rash are rarely recorded. Also rarely, the rash can take on a hemorrhagic appearance. Injection observed small vessels conjunctiva, pain when pressing on eyeballs. When examining the oropharynx, its redness and granularity are diagnosed. On palpation, there is an increase in the cervical, submandibular, and axillary lymph nodes, which are somewhat painful when pressed. Signs such as cough and runny nose are rarely diagnosed with this infection.

From the outside internal organs a decrease is recorded blood pressure, muffled heart sounds are detected, and systolic murmur is often detected in the area of ​​​​the projection of the apex of the heart. From the outside bronchopulmonary system no pathological symptoms are detected. Very rarely the disease can manifest itself inflammatory process lung tissue. Palpation of the abdomen is painful in the anterior area abdominal wall, the tongue is dry, covered with a gray or white coating. Disorders of the stomach and intestines in the form of nausea, diarrhea or constipation are recorded. When palpating the spleen and liver, moderate pain is noted.

There are several strains of West Nile virus, which cause the development of the following forms of infection:

- exanthematous form, which is manifested by the appearance of all skin the patient has a characteristic polymorphic rash, predominantly maculopapular or roseola-like, which develops approximately on the second day of the disease, regressing after a few days without traces of pigmentation. Symptoms of fever, intoxication, swollen lymph nodes, and hyperemia of the oropharynx are also characteristic;

- an influenza-like form, which in its characteristics is very similar to the viral infection of the same name, but is still accompanied by a gradual deterioration general well-being, which usually manifests itself by the 5th day of illness with the development frequent vomiting, definition meningeal symptoms, tremors and ongoing high fever that does not go away within ten days;

- the meningeal form differs from others in the manifestation of cerebral symptoms almost immediately from the moment of the disease and is characterized by headaches, constant vomiting without relief, tremor, and a decrease in all reflexes;

— the most severe and dangerous form of West Nile fever is considered meningoencephalic, which is characterized by a gradual increase in cerebral symptoms with the development of agitation, delirium, confusion, often turning into a coma. The mortality rate in this case is quite high, and after recovery, a person may experience complications such as paresis, asthenia and muscle tremors for the rest of his life.

Also, all strains of the virus that causes West Nile fever are usually divided into so-called old and new strains. Old strains include those forms of the virus that prevailed until the 90s of the twentieth century. They are characterized mainly by a benign course of the disease with a predominance of symptoms of intestinal dyspepsia, pharyngitis, conjunctivitis, and the appearance of a rash. Often, when a person is infected with this type of virus, the disease occurs in a subclinical form without any symptoms. As for new strains, they are represented by the above forms and almost always have a difficult and long-lasting course.

The most commonly diagnosed complications of infection are cerebrovascular accidents, which occur in the form of strokes, cerebral edema, development of paralysis, and paresis.

Diagnosis of West Nile fever

If you suspect West Nile fever, you must first clarify with the patient the possibility of his recent stay in areas that are endemic for this infection. The development of these symptoms during the months of active breeding of mosquitoes and ticks, namely from June to October, should also be alarming. Since the source of infection for this disease is wild and domestic birds, rodents, it is necessary to establish the possibility of contact with them in the patient’s history, which can often be associated with professional activity person.

To the main diagnostic methods of this type virus in the human body, the following laboratory techniques are used:

- a general blood test, which can record an increase in the level of leukocytes, neutrophils and the Erythrocyte Sedimentation Rate, a decrease in the number of lymphocytes, which is observed at the height of the disease, and at the very beginning of the onset of symptoms there is often a slight decrease, that is, a decrease in the number of leukocytes;

- V general analysis protein or proteinuria is detected in urine, a large number of columnar epithelium, as well as leukocyturia or the presence of leukocytes;

— when collecting biological material in the form of blood or cerebrospinal fluid, the Polymerase Chain Reaction method is often used, which makes it possible to detect pathogen RNA or its genetic material in it. This method is called genetic research;

- actively use serological diagnostic methods, which are best carried out during the first seven days of the onset of clinical symptoms, as well as 14-20 days after the first samples are taken for diagnostic comparison of the effectiveness of the treatment. Linked immunosorbent assay allows you to diagnose the presence of immunoglobulins of class M, which indicates the presence of a disease in the human body at the time of the analysis, or the determination of immunoglobulin belonging to class G, which indicates the ongoing process of recovery or a previous infection. The Complement Fixation Reaction (FFR) is aimed at identifying antigen-neutralizing antibodies in the patient’s body, which are secreted by the body at the time of recovery; they can also be detected in the case of a recent illness. The Hemagglutination Inhibition Reaction and the Neutralization Reaction show how antibodies increase in the resulting paired sera with a permissible interval of 10 days;

- when carrying out lumbar puncture note changes that, depending on belonging to a particular strain of the virus, will differ slightly from each other, for example, with the influenza form the only symptom- this is an increase in the pressure under which the cerebrospinal fluid flows, and the meningeal form is characterized by such signs as cytosis with the number of cells from 15 to 1000 in one microliter, predominantly of a mixed nature, although a characteristic sign of the onset of the disease is the predominance of neutrophils in the spinal cord fluid. This feature may be associated with the death of neurons. Also characterized by an increase in fluid pressure, an increase in protein to 1 gram per liter, and an increase in glucose. Sanitation of the cerebrospinal fluid is usually impaired.

Differential diagnosis must be carefully carried out with diseases such as acute respiratory viral infections, rickettsiosis, toxoplasmosis, acute lymphocytic choriomeningitis.

Treatment for West Nile fever

West Nile fever is caused by a virus for which no vaccine or drug has yet been developed. Although this is a viral disease, conventional antiviral drugs medicines cannot lead to its elimination and their use in treatment does not give the desired effect. Consequently, therapy for this infection comes down to only symptomatic elimination of the patient’s symptoms. The duration of therapy is usually about 10 days; in case of damage to the nervous system and the development of corresponding disorders, treatment is extended for a period of 1 month.

The main medications used in the treatment of West Nile fever are:

— Prescribing intravenous drip injections with solutions of Reopoliglucin, Trisol, and, if necessary, Albumin, helps replenish lost volumes of fluid in the body with fever, diarrhea and vomiting;

- To improve cerebral circulation, inject special means, for example, Pentoxifylline, Trental;

— If concomitant bacterial complications are detected, it is recommended to antibacterial therapy;

- Sometimes treatment is not complete without a prescription anticonvulsants, the most famous of which is Relanium;

— Sedatives, antioxidants often also have to be prescribed in case of complications with the development neurological symptoms;

- In cases of increase intracranial pressure with the risk of developing cerebral edema, the administration of Mannitol with Veroshpiron or with Furosemide is prescribed, but only together with drugs containing potassium, since the latter very actively removes this microelement from the human body, which can also aggravate clinical picture illness;

— Often, when damage to the central nervous system develops, it is necessary to resort to the introduction hormonal drugs, for example, Dexamethasone, which becomes decisive for rapidly developing cerebral edema;

— During development respiratory failure with severe shortness of breath, hypoxia, hypocapnia or hypercapnia, the patient falling into a coma, the development of generalized seizures, mandatory connection to the device is recommended artificial ventilation lungs or mechanical ventilation.

An important point in the treatment of West Nile fever is not only the prescription of appropriate drugs, but also careful monitoring of the indicators of the function of the circulatory system, urinary system, and respiratory organs.

As a rule, the recovery process is quite long, but if the infection is diagnosed in a timely manner and therapy is prescribed, the prognosis is favorable. It should be remembered that relapses of the disease are often recorded, which characterizes the undulating course of West Nile fever. The first relapse of the disease is represented by neurological symptoms, the second is associated with disturbances in the functioning of the circulatory system, and the third manifests itself catarrhal symptoms. Deaths are possible, but quite rare.

All patients who have been diagnosed with any neurological disorders after discharge from the hospital are subject to dispensary observation.

Very important stage is the prevention of infection with West Nile fever, which should be aimed, first of all, at preventing the bites of mosquitoes and ticks that are its carriers, in the case of a tick being sucked on - at its timely removal and obligatory referral for examination for infection. Important aspects include the use of protective repellents when staying outdoors, wearing long sleeves, especially in the evening, when mosquitoes are considered to be most active. A useful means of protection against mosquitoes would be to install special screens and mosquito nets on doors and windows. It is also important to take precautions that will not allow mosquitoes to breed near human habitation: do not allow water to accumulate for a long time in buckets, flower pots, tires near the house, be sure to drain the water from children's pools after swimming, as well as at night, constantly change the water that Pets drink from special sippy cups.

As for preventive measures at the urban or rural level, it is necessary to periodically disinfest abandoned buildings and basements on city streets, and treat places where arthropods are expected to hatch with special anti-mosquito preparations, especially near recreation areas. Measures are often taken to reduce the populations of birds belonging to the synanthropic group (pigeons, crows, sparrows).

West Nile fever - which doctor will help? If you suspect infection with this fever, you should immediately contact a doctor such as an infectious disease specialist.