Health Department Reports First Human Cases of West Nile Virus for 2020 Season, Reminds New Yorkers to Reduce Exposure to Mosquitoes

Surveillance has detected West Nile virus in mosquitoes collected throughout the five boroughs

The Health Department is aggressively spraying parts of the city where mosquito activity is prevalent; there have been 11 adulticiding spray operations, 2 aerial larvicidings and 1,293 ground-based larvicidings to date

September 24, 2020 — The Health Department today reported the first West Nile virus infections of the 2020 season and one death. Six New Yorkers have been diagnosed with West Nile virus infections: two from Queens, two from Manhattan, and one each from Staten Island and Brooklyn. One person from Manhattan is thought to have been infected while traveling out of NYC. All six were admitted to the hospital; five were discharged and one person has died. The decedent was over 65 years old and age is a well-known risk factor for severe West Nile virus outcomes. This is the first death from West Nile virus infection in New York City since 2018.

Every year since 1999, people in New York City are diagnosed with West Nile virus infection, with most identified between late July and October. The amount of West Nile virus activity varies every year. Mosquito populations this year are at an average level compared to previous years; the number of mosquito pools testing positive for West Nile virus this season is 413, which is 15% more than last year at this point in time. So far this season, the Health Department has completed 11 adulticiding spray operations and two aerial larvicide treatments to reduce the risk of West Nile virus. Additional mosquito treatments are planned for the remainder of the mosquito season with locations to be determined by the Health Department’s extensive citywide surveillance system.

In individuals over 50 or with a weakened immune system, West Nile virus can cause severe illness, including meningitis and encephalitis, sometimes resulting in permanent or long-term complications such as muscle weakness, fatigue, confusion and depression. Others may experience milder symptoms, which include headache, fever, fatigue, and rash. New Yorkers can learn more about West Nile virus and how to protect themselves from mosquito bites here.

“We mourn the loss of a fellow New Yorker and urge everyone to take simple precautions to keep themselves and their families safe from mosquito bites,” said Health Commissioner Dr. Dave Chokshi. “When outside, wear mosquito repellent, cover your arms and legs, and discard standing water and install window screens to reduce your risk.”

The West Nile virus was first detected in New York City 20 years ago. Since 1999, the number of human cases has ranged from three to 47 annually. Ten New Yorkers were diagnosed with West Nile virus during the 2019 season. Of the 434 New Yorkers diagnosed with West Nile virus since 1999, 47 (11%) have died due to their infection. The number of positive mosquito pools has also varied annually from 40 to 1,024. New York City has over 47 species of mosquitoes, but West Nile virus is transmitted primarily by several Culex species, including Culex salinarius, Culex pipiens and Culex restuans.

The Health Department has successfully helped control mosquito-borne diseases with regular mosquito surveillance throughout the early spring and summer. Currently, there are 106 surveillance traps in the five boroughs. The agency’s mosquito control efforts are data driven and rely on our mosquito trapping and testing results to determine areas of the city to spray pesticide and apply larvicide. The Health Department will increase spraying in neighborhoods that meet these criteria. Department employees use trucks or backpack sprayers to kill adult flying mosquitos.

As a part of normal outreach, the Health Department conducts 80 to 90 presentations to educate communities about mosquito-borne illnesses. This year, due to COVID-19 related restrictions, the Department conducted a reduced number of virtual presentations. Community presentations on West Nile virus and other health topics can be requested here.

Reducing exposure to mosquitoes

  • Use an approved insect repellent containing DEET, picaridin, oil of lemon eucalyptus (not for children under 3 years of age), or products that contain the active ingredient IR3535.
  • Make sure windows have screens. Repair or replace screens that have tears or holes.
  • Eliminate any standing water from your property and dispose of containers that can collect water. Standing water is a violation of the New York City Health Code.
  • Make sure roof gutters are clean and draining properly.
  • Clean and chlorinate swimming pools, outdoor saunas and hot tubs. Keep them empty or covered if not in use. Drain water that collects in pool covers.
  • Report standing water by calling 311. For more information about West Nile virus, call 311 or visit To received updates on West Nile virus activity and control effects in the City, please register to receive direct alerts by landline or text messaging through Notify NYC. You can also follow the DOHMH’s social media at @NYCHealthy at Twitter, Instagram, and Facebook.



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