West Nile encephalitis is a type of brain inflammation caused by the West Nile virus. The infection is contracted trough the bite of the infected mosquito ( above all the Culex pipiens mosquito) i.e. the mosquito that carries the West Mile virus.
Transmission of the Virus
In order to get infected an individual must be bitten by an infected mosquito, the one that carries the virus. In majority of cases the very mosquitoes get infected by feeding on birds which are the primary source of the virus. Such birds may or may not develop infection. The birds are vectors as well as mosquitoes, meaning that they actually represent intermediate carriers of the virus.
It is estimated that the crow is the most common bird species infected with the West Nile virus. Crows generally die due to viral infection. Apart from crows the virus also affects sparrows.
After feeding on blood of the infected animals, mosquitoes may easily spread the infection to humans whose blood they also drink.
After being bitten, there is an incubation period of approximately 1-6 days ( in immunocompromised people up to 16 days). After incubation patients develop symptoms and signs of the infection.
The infection is not contagious i.e. there is no interhuman transmission.
West Nile Encephalitis Symptoms and Signs
Unfortunately, not all patients provide a history of a mosquito bite. Even though majority of people are actually asymptomatic, there is also a chance that people infected with the West Nile virus develop flu-like symptoms. Only small number of people develop neurological disease.
Most patients complain about gastrointestinal problems like nausea, vomiting and diarrhea. There may be a lot of non-specific symptoms that also occur in other infections and conditions. For instance, one may complain about sore throat, backache, myalgia or arthralgia.
Patients who have developed encephalitis may additionally develop meningitis and end up with meningoencephalitis. In such case the symptoms may vary a lot and increased body temperature, mental confusion, tremor and flaccid paralysis are only some of them. Symptoms and signs are more severe in young patients as well as elderly individuals.
West Nile Encephalitis Prognosis
In healthy individuals the condition does not cause any complication and they are completely cured. Additional health issues and complications affect only elderly people and those already suffering from some diseases (usually the chronic ones).
The most severe complication of all is death. Furthermore, encephalitis may cause irreversible damage to certain structures of the nervous system and lead to neurological sequelae.