Infectious Disease Compendium

West Nile Virus


A virus.

Diagnose with CSF and blood serology/IgM.

Epidemiologic Risks

Spread by mosquito bite, found in birds.

It likely came over from the Middle East in 1999 and over the next decade spread west across the US and is now in every state.

If yu dead crows and jays, look out for WNV. These birds are more susceptible to death from this virus. When the birds are not available for dinner, the mosquito feeds on humans.


Meningitis, encephalitis, can mimic polio, most are asymptomatic.

Patients who have a deletion in the CCR5 chemokine are much more likely to get encephalitis (PubMed), but less able to get HIV. Win one, lose one.

As of 2010, the CDC is reporting the that incidence for neuroinvasive disease has decreased five fold: 1.02 to 0.23 per 100,000 population between 2002 and 2008. Is the organism mutating?

A small subset of patients can be ill for years and have virus isolated from urine (PubMed).




One of the downsides of the last economic downturn was more West Nile: "Adjustable rate mortgages and the downturn in the California housing market caused a 300% increase in notices of delinquency in Bakersfield, Kern County. This led to large numbers of neglected swimming pools, which were associated with a 276% increase in the number of human West Nile virus cases during the summer of 2007 (PubMed)."

Last Update: 05/03/18.