West Nile fever
Introduction
West Nile Hot Introduction West Nilefever is an acute febrile disease transmitted by mosquitoes of West Nile virus, which can invade the central nervous system and cause encephalitis. In Africa, southern Europe, the Middle East, Central Asia and West Asia, Oceania and other places are endemic. The main clinical manifestations are fever, rash and lymphadenopathy, which invade the central nervous system and can produce symptoms of encephalitis. basic knowledge The proportion of sickness: 0.007% Susceptible people: no specific population Mode of infection: contact spread Complications: respiratory failure, myocarditis, pancreatitis, hepatitis
Cause
West Nile fever
(1) Causes of the disease
The West Nile fever virus is a West Nile virus strain of the Flavivirus family of Flavivirus. It was first isolated from the blood of a hot adult woman in the West Nile region of Uganda, Africa in 1937. It was named in the West Nile region. West Nile virus, its antigenicity and cross-reaction with Japanese encephalitis, St. Louis encephalitis, Moray Valley encephalitis, Kunjin virus, the virus diameter of 21 ~ 35nm, round particles, with the outer membrane, by multiple A icosahedron composed of a sheath protein, a single-stranded RNA consisting of approximately 12,000 nucleotides in the nucleus. The West Nile fever virus can be genetically classified into two types, only the type 1 virus is associated with human encephalitis, and the type 1 virus Already isolated in Africa, Europe, Asia and North America, type 2 virus causes endemic animal diseases in Africa, and has nothing to do with human encephalitis. West Nile fever virus can multiply in the brain of suckling mice and culture passage, the virus can be in chicken It replicates in the embryo and forms acne on the chorioallantoic membrane. It is sensitive to ether and sodium deoxycholate. The optimum pH is 6.6. The optimum temperature is 37 ° C. It is resistant to low temperature and dryness. It is freeze-dried. Method can be saved at 4 ° C Years.
(two) pathogenesis
When a mosquito bites a bird infected with the West Nile fever virus, it develops and matures after 10 to 14 days. The virus is located in the parotid gland of the mosquito, and the virus is transmitted to humans or animals during the bite, causing disease or recessive infection. It enters the brain parenchyma through the blood-brain barrier, causing fever or symptoms of encephalitis.
Prevention
West Nile Heat Prevention
1. Protect susceptible populations.
In the epidemic areas where West Nile virus disease outbreaks, residents are reminded of less outdoor activities. Long-sleeved clothes should be worn outdoors, and exposed skin should be coated with mosquito repellent. Pay attention to the installation of screens and screen doors to reduce the chance of mosquitoes entering the room. At the same time, you can use electric mosquito coils and electric mosquito swatter to kill adult mosquitoes indoors.
2. Isolation of the patient.
Although it is currently considered relatively unlikely that humans will spread West Nile virus through mosquitoes and blood-sucking hedgehogs, for the sake of safety, patients should be isolated and mosquito nets should be installed to prevent mosquitoes and hedges from spreading.
3. Cut off the source of infection.
For the control of vector mosquitoes, comprehensive prevention and control methods should be adopted to reduce the density of vector mosquitoes as much as possible. Immediately after the outbreak of West Nile virus disease, the prevention and control measures of vector mosquitoes began.
Complication
West Nile Thermal Complications Complications, respiratory failure, myocarditis, pancreatitis, hepatitis
Encephalitis can be complicated by dyspnea until respiratory failure, occasional skin blisters, acute spinal anterior polio, myocarditis, pancreatitis, hepatitis, etc.
Symptom
West Nile fever symptoms common symptoms high fever cold war plaque rash rash difficulty appetite lacking congestion inguinal lymph node swelling nausea abdominal pain
The incubation period of this disease is 1 to 6 days, some of which lasts for 20 days. The clinical manifestations are fever type and encephalitis type. Both types have sudden onset, and the body temperature suddenly rises to 40 °C. Some patients are accompanied by chills.
Heat type
Sudden fever, more manifested as double wave heat, headache, eye pain, body muscle aches, may be associated with pharyngitis and nausea, vomiting, abdominal pain, diarrhea, loss of appetite and other gastrointestinal symptoms, high fever can cause facial flushing, conjunctival congestion, underarm and Inguinal lymph nodes are swollen, no obvious tenderness, about half of the patients have rashes, rashes occur at the end of the fever period or fever, and there are reddish rose rashes or maculopapular rashes on the back of the neck, trunk and limbs. The duration is about 1 week, and the self subsides. Light cases have only a cold-like process, and the systemic response is light, showing self-limiting, 80% of patients self-healing after 3 to 6 days.
2. Encephalitis type
A small number of patients, especially the elderly and some children, can cause encephalitis and meningitis after infection. At this time, the condition is heavier, the body temperature rises sharply, does not fall continuously, severe headache, nausea, vomiting, lethargy, and then unconsciousness, neck Tonic, abnormal neuroreflexes, trembling of the limbs, paralysis, convulsions, coma, difficulty breathing, and respiratory and circulatory failure.
Occasionally, skin blisters, acute spinal anterior polio, myocarditis, pancreatitis, hepatitis, etc., lymph node swelling often takes several months.
Examine
West Nile Hot Check
General laboratory examination: leukopenia, encephalitis type of lymphocytes in the cerebrospinal fluid increased, protein increased.
Immunological examination
Serological antibody detection method, commonly used ELISA method, the patient's acute phase and recovery period of two sera, two serum simultaneously tested, in the recovery phase serum than the acute phase-specific IgG antibody titer increased more than 4 times positive. Helps diagnose the disease.
2. Pathogen examination
From the latent period to the fifth day after the onset, the virus positive rate was higher from the blood or cerebrospinal fluid of the patient. The identification of the newly isolated virus was generally carried out by using known serum for neutralization experiments.
3. Molecular biology examination
RT-PCR was used to detect the serum or cerebrospinal fluid samples by RT-PCR for the specific primers of West Nile fever virus. The positive rate was high and the diagnostic value was specific.
Diagnosis
West Nile Thermal Diagnosis
Relying on epidemiological data, in epidemic areas, patients with fever, rash and swollen lymph nodes in the epidemic season, especially those with symptoms of encephalitis, should consider the possibility of the disease.
Two serum-specific hemagglutination antibody assays should be performed, and virus isolation or RT-PCR assays can be used to facilitate the diagnosis of this disease. The disease needs to be differentiated from epidemic encephalitis.
