West Nile Fever

What is West Nile Fever?

West Nile fever (syn: West Nile encephalitis, West Nile encephalitis, Nile encephalitis, West Nile fever, Encephalitis Nili occidentalis – Latin; West-Nile encephalitis – English) is an acute transmissible viral disease characterized by snooper cases, which has a snooper, and it is still pending, characterized by a snooper, it has a snooper, it has a snooper, it has a snooper, it has a snooper, it is still perennial, it is still pending, it is characterized by snooperphalitis. membranes (very rarely – meningoencephalitis), systemic lesions of the mucous membranes, lymphadenopathy and, less commonly, rash.

For the first time, the West Nile fever virus was isolated from the blood of a sick person in 1937 in Uganda. Subsequently, there were indications of a widespread disease in Africa and Asia. The most common disease is found in the Mediterranean countries, especially in Israel and Egypt. Cases of the disease are described in France – on the Mediterranean coast and in Corsica, as well as in India and Indonesia. Proved the existence of natural foci of the disease in the southern regions of the former USSR – Armenia, Turkmenistan, Tajikistan, Azerbaijan, Kazakhstan, Moldova, Astrakhan, Odessa, Omsk regions, etc.

Causes of West Nile Fever

The causative agent of fever of the Western Nile is a flavivirus of group B of the Togavirus family, sizes – 20-30 nm, contains RNA, has a spherical shape. Well preserved in frozen and dried condition. Dies at temperatures above 56 ° C for 30 minutes. Inactivated by ether and desoxycholate. It has hemagglutination properties.

The carriers of the virus are mosquitoes, ixodic and argas mites, and the reservoir of infection is birds and rodents. West Nile fever has a distinct seasonality – late summer and autumn. Most people get sick of young age.

The risk of disease is higher in people older than 50 years. The likelihood of serious symptoms of a flat-hole worm in the case of the disease is higher in people over 50 years of age, and they should be especially wary of mosquito bites.

Being on the air, you are at risk. The more time you spend on the air, the longer the time during which an infected mosquito can bite you. If you spend a lot of time outdoors due to work or rest, make sure that mosquitoes do not bite you.

The risk of illness from a medical procedure is very low. Before use, all donated blood is checked for the presence of an LZN virus. The risk of infection with an IVH through blood transfusion or organ transplantation is very low, so people who need an operation should not refuse it because of this risk. If you’re worried about something, talk to your doctor.

Pregnancy and breastfeeding does not increase the risk of infection with West Nile fever. Researchers have not yet come to a final conclusion as to what the risk of an LZN poses to a fetus or an infant who becomes infected through mother’s milk. If you have concerns, talk to your doctor or nurse.

Pathogenesis during West Nile Fever

The pathogenesis of the West Nile fever remains poorly understood. The virus enters the bloodstream of a person with a mosquito bite. The virus then hematogenously disseminates, causing systemic lesions of the lymphoid tissues (lymphadenopathy). With the penetration of the virus through the blood-brain barrier, damage to the membranes and substances of the brain with the development of meningoencephalitis are possible. There are cases of latent infection.

The reservoir and sources of infection are wild and domestic birds, rodents, bats, mosquitoes, ticks.

The transmission mechanism is transmissible, disease carriers are the mosquitoes of the genus Culex, as well as argas and ixodid mites.

The natural susceptibility of people is high. Post-infectious immunity is stressful and resistant.

Major epidemiological signs. The disease is endemic in many countries in Asia, Europe, and Africa. Described hundreds of cases of fever in Israel and South Africa. The most significant African epidemic (about 3 thousand cases) was noted in the Cape Province after heavy rains in 1974. Other outbreaks were observed in Algeria, Azerbaijan, Central African Republic, Zaire, Egypt, Ethiopia, India, Nigeria, Pakistan, Senegal, Sudan , Romania, the Czech Republic, etc. In 1999, an outbreak of fever (380 people fell ill) with laboratory confirmation of the disease was observed in the Volgograd Region. Virus antigens are found in selectively captured mosquitoes of the genus Culex and ticks. The area of ​​risk for West Nile fever is the Mediterranean basin, where birds arrive from Africa. The disease has a distinct seasonality – late summer and autumn. Mostly rural residents are sick, although in France, where this disease is known as “duck fever”, urban residents who come to hunt in the Rhone Valley are getting sick. More often ill persons of young age. There are cases of laboratory infection.

Symptoms of West Nile Fever

The incubation period ranges from several days to 2-3 weeks (usually 3-6 days). The disease begins acutely with a rapid increase in body temperature to 38-40 ° C, accompanied by chills. In some patients, an increase in body temperature is preceded by short-term effects in the form of general weakness, loss of appetite, fatigue, and feelings of tension in the muscles, especially in the calf, sweating, and headaches. The febrile period lasts on average 5-7 days, although it can be very short – 1-2 days. The temperature curve in typical cases is remittent in nature with occasional chills and excessive sweating, which does not bring patients with improved well-being.

The disease is characterized by pronounced phenomena of general intoxication: severe excruciating headache with a predominant localization in the area of ​​the forehead and orbits, pain in the eyeballs, generalized muscle pain. Particularly severe pain is noted in the muscles of the neck and lower back. Many patients have moderate pain in the joints of the limbs, swelling of the joints is not observed. At the height of intoxication, frequent vomiting often occurs, there is no appetite, pain in the region of the heart, a feeling of fading, and other discomfort in the left half of the chest. Drowsiness may occur.

The skin is usually hyperemic, maculopapular rash is sometimes observed (5% of cases). Rarely, usually with prolonged and undulating fever, a rash may become hemorrhagic. Almost all patients revealed marked hyperemia of the conjunctiva of the eyelids and a uniform injection of the vessels of the conjunctiva of the eyeballs. Applying pressure to the eyeballs is painful. In most patients, hyperemia and granularity of the mucous membranes of the soft and hard palate are determined. However, nasal congestion and dry cough are relatively rare. An increase in peripheral lymph nodes (usually submandibular, mandibular, lateral cervical, axillary and cubital) is often observed. Lymph nodes are sensitive, or slightly painful on palpation (polylimphadenitis).

There is a tendency to arterial hypotension, muffled tones of the heart, at the top a rough systolic murmur can be heard. On the ECG, signs of myocardial hypoxia in the apex and septum, focal changes, and slowing of atrioventricular conduction can be detected. Pathological changes in the lungs, as a rule, are absent. Very rarely (0.3-0.5%) can pneumonia develop. The tongue is usually coated with a thick grayish-white bloom, dry. Palpation of the abdomen is often determined spilled pain in the muscles of the anterior abdominal wall. There is a tendency to delay the chair. In about half of the cases, a moderate increase and sensitivity to palpation of the liver and spleen are detected. Gastrointestinal disorders may be observed (often enteritis-type diarrhea without abdominal pain).

Against the background of the clinical manifestations described above, serous meningitis syndrome is found (in 50% of patients). It is characterized by dissociation between mild shell symptoms (stiffness of the muscles of the neck, Kernig’s symptom, less often the symptoms of Brudzinsky) and distinct inflammatory changes in the CSF (pleocytosis up to 100-200 cells in 1 μl, 70-90% lymphocytes); perhaps a slight increase in protein content. Characterized by diffuse focal neurological microsymptomatics (horizontal nystagmus, proboscis reflex, Marinescu-Radovici symptom, slight asymmetry of the palpebral fissures, decrease in tendon reflexes, absence of abdominal reflexes, diffuse decrease in muscle tone. In some patients, symptoms of radiculoalgia with no signs of reflexes, diffuse decrease in muscle tone. In some patients, symptoms of radiculoalgia with no signs of reflexes, diffuse decrease in muscle tone. rarely, but long-term signs of mixed somatocerebral asthenia persist (general weakness, sweating, mental depression, sleeplessness Itza, memory loss).

Neuroinfective form of West Nile fever. The most common lesion. Characteristic acute onset with fever up to 38-40 ° C, chills, weakness, sweating, headaches, sometimes arthralgia and back pain. Persistent symptoms include nausea, repeated vomiting (up to 3-5 times per day), not associated with food intake. Less commonly, the significantly pronounced symptoms of toxic encephalopathy are observed – excruciating headache, dizziness, psychomotor agitation, inadequate behavior, hallucinations, and tremors. Clinical manifestations of meningism, serous meningitis, and in some cases, meningoencephalitis may develop. The duration of the fever varies from 7-10 days to several weeks. After its decrease according to the type of accelerated lysis during the recovery period, the patients’ condition improves gradually, but weakness, insomnia, depressed mood, and weakening of memory persist for a long time.

Flu-like form of West Nile fever. It occurs with common infectious symptoms – fever for several days, weakness, chills, pain in the eyeballs. Sometimes patients complain of cough, a sense of rawness in the throat. On examination, the phenomena of conjunctivitis, scleritis, bright hyperemia of the palatine handles and the posterior pharyngeal wall are noted. However, dyspeptic phenomena are possible – nausea, vomiting, frequent loose stools, abdominal pain, and sometimes an enlarged liver and spleen. In general, this form of the disease occurs as an acute viral infection and is often accompanied by symptoms of meningism.

Exantmatous form of West Nile fever. Watch much less. The development of a polymorphic exanthema on the 2nd-4th day (usually spotty-papular, sometimes roseol-like or scarlet-like) is typical for feverish reactions and other general toxic symptoms, catarrhal manifestations and dyspeptic disorders. The rash disappears in a few days, leaving no pigmentation. Polyadenitis is often observed, and the lymph nodes are moderately painful on palpation.

Serious symptoms rarely occur. Approximately one in 150 people infected with LZN virus, the disease occurs in severe form. Severe symptoms include high fever, headache, stiff neck, stupor, disorientation, coma, tremors, convulsions, muscle weakness, loss of vision, numbness and paralysis. These symptoms may persist for several weeks, and the neurological exposure may be permanent.

Lighter symptoms occur in some people. Up to 20% of people who become infected suffer symptoms, including fever, headache, muscle aches, nausea, vomiting, and sometimes swelling of the lymph glands or a rash on the skin of the chest, abdomen and back. These symptoms may persist for only a few days, although there are cases when even in healthy people the disease lasted for several weeks.

Most people do not experience any symptoms. Approximately 80% of people (about 4 out of 5) who have been infected with LZN virus do not show any symptoms at all.

When a neuroinfectious form of the disease can develop swelling and swelling of the brain, disorders of cerebral circulation. With the development of meningoencephalitis, paresis and paralysis are possible, a severe course of the disease with a fatal outcome in rare cases.

Diagnosis of West Nile Fever

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

Epidemiological prerequisites can be a stay in an endemic area of ​​fever in West Nile – North and East Africa, the Mediterranean, the southern areas of our country, information about mosquitoes or ticks in these regions.

General blood and urine tests, as a rule, do not reveal pathological changes. Leukopenia can be observed, 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 elevated protein content. Laboratory interpretation is provided by the serological reactions of rtga, RAC and PH using the paired sera method. However, since many flaviviruses have a close antigenic relationship, the detection of antibodies to one of them in blood sera may be due to the circulation of another virus. The most reliable evidence of the presence of an infection caused by the West Nile virus is the detection of the pathogen. From the patient’s blood, the virus is isolated in cell culture MK-2 and in mice weighing 6-8 g (intracerebral infection). Identification of the pathogen is carried out by the direct method of fluorescent antibodies using a species-specific luminescent immunoglobulin to the West Nile virus.

Differential diagnostics should be carried out with other arbovirus infections, mycoplasmosis, ornithosis, luterellosis, toxoplasmosis, tuberculosis, rickettsiosis, syphilis, influenza and other acute respiratory diseases, enterovirus infection, acute lymphocytes, and irophiosis, acute lymphocytic infection, and other acute respiratory infections

West Nile Fever Treatment

In the acute period of the disease, patients need bed rest. They are prescribed vitamins and other fortifying agents. In patients with severe meningeal syndrome, repeated spinal puncture and steroid hormone therapy are indicated. There is no specific treatment. Conduct pathogenetic and symptomatic therapy.

Forecast. The disease has a tendency to wave-like flow. 1-2 recurrences of the disease may occur (with an interval of several days). The first wave is most often characterized by serous inflammation of the lining of the brain, the second by heart damage, and the third by catarrhal phenomena. The course of the disease is benign. Despite prolonged asthenia in the period of convalescence, recovery is complete. Residuals and deaths are not observed.

Preventing West Nile Fever

  • The easiest and safest way to prevent West Nile fever is by avoiding mosquito bites.
  • While on the air, use repellents that include DEET (N, N-diethylmethyltoluamide). Follow the directions on the packaging.
  • Many mosquitoes are most active at dusk and dawn. At this time you should use insect repellents, wear long-sleeved clothing and trousers or not go outside. On light-colored clothing, it will be easier for you to spot mosquitoes.
  • Good protective nets should be installed on windows and doors so that mosquitoes do not penetrate the house.
  • Destroy breeding sites for mosquitoes, avoiding the presence of stagnant water in flower pots, buckets and barrels. Change the water in the drinkers for pets, as well as in the bird baths every week.
  • Drill holes in the swings made of tires so that they do not accumulate water. Water pools should be poured from children’s pools and put on their side when no one uses them.

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