West Nile fever is a disease caused by a viral infection. For the first time, the virus of the West Nile fever was isolated in 1937 in Uganda. The disease is spread mostly in Africa and Asia.
The incubation period ranges from several days to 2-3 weeks but usually, it is 3-6 days. The disease starts sharply with the rapid increase in body temperature to 38-40°C and is accompanied by a fever. In some patients, the rise of body temperature is preceded by such short-term symptoms as general weakness, loss of appetite, fatigue, feeling of tension in the muscles, sweating, and headache. The febrile period lasts for 5-7 days on average, although it may be shortened to 1-2 days.
The disease is characterized by pronounced symptoms of general intoxication: a strong headache that is preferentially localized in the area of the forehead and eye sockets, pain in eyeballs and muscle pain. Particularly severe pain is observed in muscles of the neck and back. Many patients experience moderate pain in the joints of the extremities along with the further swelling of the joints. An intoxication of the organism provokes multiple vomiting, loss of appetite, pain in the heart muscle and discomfort in the left side of the chest. Drowsiness is also possible.
A rash on the skin is observed in 5% of cases. Sometimes, mostly in case of a prolonged fever, the rash may be of a hemorrhagic character. Virtually all patients suffer from a severe conjunctival hyperemia. Eyeballs are painful during pressing. The majority of patients also have a granularity of the throat mucous membrane. However, nasal congestion and dry cough are relatively rare. An increase of peripheral lymph nodes is quite frequent. Lymph nodes are sensitive or slightly painful during palpation.
Pathological changes in the lungs are usually missing. Pneumonia develops rarely, approximately in 0.3-0.5% of cases. The tongue is usually coated with a thick grayish bloom. Palpation of the abdomen often causes a diffuse pain in the muscles of the anterior abdominal wall. Approximately in half of all cases, liver and spleen are moderately increased and sensitive during the palpation. Gastrointestinal disorders may also be observed in a form of diarrhea.
Symptoms of meningitis appear after 4-5 days since the disease onset, while the fever preserves at the same level. A headache intensifies sharply, vomiting does not stop and dizziness strengthens. Weakness, tremor of the limbs and pain in the whole body prevent the patient from walking.
Further, the signs of brain damage appear. They include paresis or paralysis, confusion, changes of reflexes and disruption of the cranial nerves. These symptoms may be complicated by coma and respiratory arrest that occur in half of the cases.