West Nile Virus Detected in Delaware for First Time in 2026

State of DE - West Nile Virus has shown up in Delaware for the first time this year. The virus was found in a flock of sentinel chickens that the state uses to watch for mosquito-borne illness.

The Department of Natural Resources and Environmental Control reported the detection from a flock in eastern Kent County, Delaware. The birds were sampled on July 20, and the Division of Public Health lab confirmed the virus on July 31.

"This occurrence is slightly earlier than our typical first detection date, historically the last week in July or first week in August - but is consistent with other WNV activity thus far this summer elsewhere in the mid-Atlantic and Northeast," said Tom Moran, DNREC Mosquito Control Section Administrator.

DNREC keeps 20 flocks of sentinel chickens around the state each summer and fall, with four birds at each site. Blood samples are taken weekly and tested for West Nile and Eastern equine encephalitis. The chickens build up antibodies when bitten by infected mosquitoes, but they are not harmed, which makes them useful for tracking the virus.

Once a flock tests positive, DNREC checks the mosquito species in that area. That helps them figure out whether spraying or other control steps are needed.

No human cases of West Nile have been reported in Delaware so far this year. The state had three human cases in 2025, and one of those was fatal. Health officials say the risk continues until colder weather arrives in mid-October.

Most people who catch West Nile never feel sick. About one in five will have milder symptoms like fever, body aches, headache, nausea or a rash. A smaller number can develop serious illness that affects the nervous system.

The Delaware Department of Agriculture reported five horses tested positive for West Nile in 2025, with no cases of Eastern equine encephalitis. There is no specific drug treatment for either disease in horses, and infections can be fatal in 30% of West Nile cases and up to 90% of EEE cases. The State Veterinarian's Office is urging horse owners to make sure their animals are vaccinated and kept up to date on booster shots.

Horse owners can also help by keeping animals inside at dawn and dusk, using insect repellent made for horses, running fans in stalls, and emptying water troughs every two to three days.

Residents can do their part too by dumping out anything that holds standing water, from old tires to clogged gutters to birdbaths. Wearing long sleeves, using insect repellent with DEET, and staying inside during dawn and dusk hours can also lower the risk of a bite.

Anyone with questions about mosquitoes can call DNREC Mosquito Control in Dover at 302-739-9917. Animal health questions can go to the Department of Agriculture at 302-698-4500, and suspected human cases can be reported to the Division of Public Health at 888-295-5156.