What is West Nile fever?

West Nile fever is caused by a virus from the Flavivirus family. It is similar to the Japanese encephalitis virus. The disease is spread by birds and caused an epizootic (a disease that spreads within an animal community) among birds when it arrived in the United States. Soon after, cases appeared in horses and humans.

Symptoms

The disease usually presents with fever and muscle aches and does not progress further in most cases. However, some patients develop meningoencephalitis, an inflammation that affects the brain and meninges.

In immunocompromised patients, including the elderly who already experience immunosenescence, the disease can be severe, potentially leading to coma and even death.

Transmission

Transmission occurs through a vector: mosquitoes of the Culex genus, which are common in Brazil. After the mosquito bite, the incubation period is approximately two weeks.

Diagnosis

Diagnosis is made using molecular methods that detect viral RNA. Serological methods also exist, but they may produce cross-reactions with other flavivirus infections, such as Dengue and Zika

Treatment

Treatment is symptomatic; there is no active medication against this virus. The vast majority of patients recover spontaneously, but severe cases can result in lasting complications.

Incidence

The first documented human case in Brazil occurred in 2014, in the state of Piauí. Cases have also been reported in horses. There is no evidence of infections causing epizootics in birds. However, there is potential for this virus to circulate in the region, as the vectors are present.

The risk of an epidemic potentially exists. But so far, it has not occurred, which is curious, considering that the birds that spread the virus migrate from the Northern Hemisphere—where the virus is present in North America—to South America. For some unknown reason, we have not yet experienced epidemics of the virus in this region.

By Einstein Editorial Board