West Nile Virus Update
Seven more samples of mixed Culex mosquitoes have tested positive for West Nile virus (WNV). The samples were collected from gravid traps on August 25, 2026, in Frelinghuysen Township, Hope Township, Knowlton Township, Liberty Township (2), and Mansfield Township (2). So far this year in Warren County, there have been a total of twenty-one (21) WNV-positive mosquito samples. Positive mosquitoes have been collected from Belvidere (2), Franklin Township, Frelinghuysen Township, Greenwich Township, Hackettstown, Harmony Township, Hope Township, Knowlton Township, Liberty Township (2), Lopatcong Township (4), Mansfield Township (2), Phillipsburg, and Washington Township (3).
For West Nile virus surveillance, adult mosquitoes are collected from traps specifically designed to catch Culex mosquitoes, the type responsible for transmitting West Nile virus, particularly from bird to bird. Each sample contains up to 75 individual adult mosquitoes of the same species from a single location.
Warren County Mosquito Control Commission has been collecting and submitting mosquito samples for testing each week since the state laboratory began mosquito testing for the year on May 18, 2026. Mid-to-late August is usually the peak time for humans and other mammals to acquire this virus. Four people have been confirmed positive in New Jersey so far this year and there have been two presumptive viremic blood donors. Warren County Mosquito Control Commission staff perform larval (aquatic immature stage) mosquito control daily throughout the county. However, treatments to reduce adult mosquito populations in West Nile virus positive areas are weather permitting. Check out our website for updates.
Mosquito populations are currently very high in parts of the county due to recent rainfall events.
Residents are urged to help reduce their risk of contracting mosquito-borne diseases by following these guidelines:
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Don't produce mosquitoes on your property. Dump or drain standing water. Mosquitoes can't begin their life without water.
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Defend yourself against mosquitoes using repellents containing DEET, Picaridin, or Oil of Lemon Eucalyptus.
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Avoid being outdoors when mosquitoes are present, typically Dawn and Dusk.
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Report neglected swimming pools by calling 908-453-3585 or visiting www.warrencountymosquito.org Anonymous calls accepted. Just one neglected pool
can produce more than 1 million mosquitoes and affect people up to five miles away.
WEST NILE VIRUS INFORMATION
West Nile virus symptoms of the mild form include fever, headache, tiredness, body aches, and swollen lymph glands. While the illness can be as short as a few days, even healthy people have reported being sick for several weeks. There were two severe human cases of West Nile virus in Warren County in 2024.
Less than one percent of individuals (about 1 in 150 people) infected with West Nile virus will develop severe illness. The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent. West Nile virus infection can be fatal.
MORE INFORMATION
WNV activity in the county: https://warrencountymosquito.com/disease-surveillance/
Repellent information from the Centers for Disease Control: https://www.cdc.gov/mosquitoes/prevention/
Mosquito-borne Diseases in NJ: https://www.nj.gov/health/cd/topics/mosquitoborne.shtml
Notice of spraying to be done for adult mosquitoes in the county: https://warrencountymosquito.com/adult/
