Delaware DPH Announces 3rd Human Case of West Nile Virus for 2021

DOVER, DE (STL.News) The Division of Public Health (DPH) announced today that an 87-year-old Kent County woman has become infected with West Nile Virus (WNV), making it the state’s third case of human WNV in 2021.  The woman indicated no travel history that could have led to transmission, meaning she contracted WNV in Delaware.  To protect the patient’s privacy, DPH will not provide additional information on this case.

WNV is a mosquito-borne illness that can cause serious health problems.  WNV is transmitted by mosquitoes, generally in summer and fall, with a peak period for disease transmissions from mid-August to mid-October.  Nearly 80 percent of people infected with WNV will not become ill.  While only a little less than 20 percent of those infected with the virus will develop West Nile fever with mild symptoms (fever, headache, body aches, a skin rash on the chest or back and swollen lymph glands), one in 150 people infected will develop severe infection (West Nile encephalitis or meningitis).

Symptoms of severe WNV infection include headache, high fever, stiff neck, and/or tremors and muscle weakness.  The elderly and those with weakened immune systems are most at risk.  Anyone who experiences any of these severe symptoms should seek medical help immediately.  Symptoms may progress to stupor, disorientation, coma, convulsions, paralysis and possibly death.

The mosquitoes that cause WNV bite primarily from dusk (evening) to dawn (morning).  However, other mosquitoes that cause diseases such as chikungunya, dengue fever, and Zika can bite during the day.  It is important to protect yourself by wearing insect repellent whenever you go outdoors.  It’s also recommended to wear light-colored, long-sleeved shirts and pants to protect your limbs from insect bites.

In addition to the three human WNV cases, there has been one confirmed case of West Nile Virus (WNV) in a Kent County horse.  West Nile Virus and Eastern Equine Encephalitis (EEE) are diseases transmitted to horses via the bites of mosquitoes.  Humans can also be infected with WNV and EEE, but transmission requires a mosquito bite, and the virus cannot be directly transmitted between horses, or between horses and people.  Signs of infection in horses include fever (although not always with WNV), anorexia, head pressing, depression or personality change, wobbling or staggering, weakness, blindness, convulsions, muscle spasms in the head and neck, or hind-limb weakness.  If owners notice any of these signs in their horses, they should contact their veterinarian immediately.

Horse owners can take several additional steps in the barn and around the farm to help protect horses from mosquito bites.  Horses should be kept inside during dawn and dusk, which are peak hours for mosquito activity.  Topical insect repellents labeled for use on horses may be applied.  The wind generated by fans installed in horse stalls can also help deter mosquitoes.  Old tires and containers should be disposed of, and standing water eliminated.  Water troughs or buckets should be emptied, cleaned, and refilled every 2-3 days if possible to remove any mosquito eggs or larvae.

Mosquito Bite Prevention: To avoid mosquito bites and reduce the risk of infection, individuals should:

  • Use Environmental Protection Agency (EPA)-registered insect repellents.  Follow the manufacturer’s instructions for reapplication times.
  • If using sunscreen, apply it first and insect repellent second.
  • Adults: Spray insect repellent onto your hands and then apply it to the child’s face. Do not apply insect repellent onto a child’s hands, eyes, mouth, or on cut or irritated skin.
  • Do not use insect repellent on babies younger than 2 months of age.
  • When outside, wear shoes, light-colored long-sleeved shirts and pants. Dress your child in clothing that covers arms and legs. Mosquito netting can protect one’s face and neck, and infants in carriages, strollers and playpens.
  • Use permethrin (an insecticide) to treat clothing and gear (such as boots, pants, socks, and tents), but do not apply to skin.
  • Prevent mosquitoes from entering the house by using screens and keeping windows and doorways tightly sealed.

The Department of Natural Resources and Environmental Control’s (DNREC) Mosquito Control section announced WNV had been found in sentinel chickens for the first time this year in July.  Delawareans are reminded that the possibility of contracting mosquito-transmitted diseases, including WNV and EEE, will continue until colder weather sets in, which this year could be as late as mid-November.  Until that time, in response to findings of WNV or EEE in humans or horses by the Division of Public Health and Delaware Department of Agriculture, respectively, DNREC’s Mosquito Control section typically increases its mosquito population surveillance efforts in the vicinity of the virus findings, and then, depending on types and numbers of mosquitoes encountered, takes appropriate mosquito control measures as warranted.  To report suspected cases of human WNV, call the DPH Office of Infectious Disease Epidemiology at 1-888-295-5156.

For more information about mosquitoes and mosquito-borne illnesses, use the following resources:

  • For mosquito biology/ecology and control, contact the DNREC Mosquito Control section office in Dover at 302-739-9917.
  • For requests for mosquito relief in upstate areas from Dover north, contact Mosquito Control’s Glasgow field office at 302-836-2555.
  • For requests for mosquito relief in downstate areas south of Dover, contact Mosquito Control’s Milford field office at 302-422-1512.
  • For animal health questions, contact the Delaware Department of Agriculture’s Poultry and Animal Health Section at 302-698-4561.