West Nile Virus Reports, Results and Summaries

2020 Positive Results Summary

WNV Positive Results All NYC Bronx Brooklyn Manhattan Queens Staten Island

Mosquito Pools

446 31 72 12 172 159
Human Cases #
West Nile Neuroinvasive Disease* 6 0 1 3 1
West Nile Fever** 1 0 0 0 1
Blood donor*** 1 0 1 0 0 0


* Cases of West Nile Encephalitis or Meningitis, or Acute Flaccid Paralysis (severe muscle weakness associated with West Nile virus infection).

** Cases with WN virus infection associated with mild to moderate illness but no evidence of central nervous system involvement.

*** Blood donors are people who had no symptoms at the time of donating blood (people with symptoms are deferred from donating) through a blood collection agency, but whose blood tested positive when screened for the presence of West Nile virus. Since they do not meet the national case definition for WNV infection, they are not included in the total human case count.

Not all animals testing positive are necessarily ill or symptomatic of WNV infection. Some specimens are tested only for surveillance purposes.

# Borough reported for human cases is determined by where the case patient resides and may not always reflect where the case patient was actually infected.

Mosquito Pools: Mosquitoes are collected from over 90 locations Citywide and tested by the New York City Department of Health & Mental Hygiene.

Human Cases: Healthcare providers in New York City are required to report all patients hospitalized with viral encephalitis and meningitis to the Department of Health & Mental Hygiene. Blood and spinal fluid specimens are tested for West Nile virus by the New York City Department of Health & Mental Hygiene.

Risk from Standing Water

While the Health Department's surveillance efforts are able to confirm evidence of West Nile virus in mosquitoes in the above mentioned areas, given the widespread presence of the virus, it should be protected against in all areas of New York City where the virus is just as likely to be detected. Residents of New York City can help reduce the risk of West Nile virus by eliminating areas of standing water and by taking precautions against mosquitoes.

For more information about West Nile virus, call 311.