DOVER (Oct. 8, 2021) – The Division of Public Health (DPH) announced today that a 79-year-old Sussex County woman has become infected with West Nile Virus (WNV), the state’s second case of human WNV in 2021. An epidemiological investigation is currently ongoing to confirm any travel history or sources that could have led to transmission. To protect the patient’s privacy, no more information will be provided on the individual at this time.

“As mosquito season continues through the fall months, it is important for everyone to take proper precautions when going outdoors in an environment where mosquitoes are prevalent,” said DPH Director Dr. Karyl Rattay. “Wearing insect repellent and wearing light-colored, long-sleeved shirts and pants are easy measures to take that can protect against this serious and sometimes deadly virus.”

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.

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.

In addition, the Office of the State Veterinarian has announced a confirmed case of West Nile Virus (WNV) in a horse. The infected horse was a 3-year-old Standardbred gelding residing in Kent County. The horse began showing signs of weakness in the hind limbs, with fever and respiratory signs on Oct. 1. The gelding lost the ability to stand and was therefore euthanized on Oct. 5. Samples were submitted to the Delaware Public Health Laboratory on Oct. 6, which confirmed the diagnosis of WNV on Oct. 7. The affected horse was not currently vaccinated against WNV.

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.

“It is essential that owners of horses and other equines work with their veterinarian to set up a routine vaccination protocol to help prevent West Nile Virus and Eastern Equine Encephalitis,” said Dr. Karen Lopez, Deputy State Veterinarian. “Unfortunately, neither disease has a specific drug treatment. Eastern Equine Encephalitis infections are fatal in 70 to 90 percent of the cases, and West Nile Virus is fatal in 30 percent of the horses that contract it.”

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 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 autumn temperatures in mid-October or later. 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.
• To report suspected cases of human WNV, call the Division of Public Health Office of Infectious Disease Epidemiology toll-free at 1-888-295-5156.
• For more information on West Nile virus or Eastern equine encephalitis, visit www.cdc.gov/ncidod/dvbid/westnile/index.htm.

For more information on what you can do to prevent West Nile Virus, visit the Centers For Disease Control and Prevention’s website, www.cdc.gov/westnile/prevention/index.html.

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