West nile virus natural history

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Natural history

The first isolation of West Nile Virus occurred in 1937 in a febrile woman in the province of Uganda. Further investigations showed that the virus cycled in Africa between species of birds and species of mosquitoes. The original manifestation appeared to be nothing more than a mild dengue-like fever. These manifestations were nothing more than a fever, malaise, rash, and lymphadenopathy.

In the 1950s, there were also outbreaks of West Nile Virus. On rare occasions, these patients would have nuchal rigidity and pleocytosis. These symptoms were first associated with meningitis because encephalitis was not recorded at this point in time.

In New York City, in 1952, there was the first documented case of human encephalitis caused by West Nile Virus. This happened when 95 patients with advanced stages of cancer were inoculated with an Egyptian strain of the virus. It was believed that this strain of the virus could actually have an oncolytic effect. In 9 of these patients, [[encephalitis] developed. The virus was also found in the spinal fluid of 3 patients and encephalitis was seen in the autopsy of one of the patients.

Possible Complications

Complications from mild West Nile virus infection are very rare.

Complications from severe West Nile virus infection include:

• Brain damage
• Permanent muscle weakness (sometimes similar to polio)
• Death
• Dysphagia
• Deep venous thrombosis
• Pressure ulcers

Prognosis

In general, the outcome of a mild West Nile virus infection is excellent.

For patients with severe cases of West Nile virus infection, the outlook is more uncertain. West Nile encephalitis or meningitis may lead to brain damage and death. Approximately 10% of patients with brain inflammation do not survive.