Missouri's Reported First Cases Of Human West Nile Virus

Ruzanna Harutyunyan's picture

The first verified human case of West Nile virus (WNV) this year has been reported to the Missouri Department of Health and Senior Services (DHSS). The first report of acute WNV infection is in a 52 year-old man in St. Louis County.

The July to August timeframe for Missouri’s first WNV human cases has become typical over the past few years. Missouri’s WNV case numbers typically rise in August and September and then decline with cooling weather. As with ticks, mosquitoes remain active and can still spread disease until the first hard frosts and freezes, so it is important for Missourians to protect themselves from mosquito bites through the fall and even early winter.

“We now see WNV every year in Missouri and anyone can be at risk of serious health problems from WNV infection. Prevention is still the best medicine, so people should take some very common-sense but effective steps to reduce their risk of infection,” said Dr. Howard Pue, State Public Health Veterinarian.

“Missourians must remember that WNV is now here to stay and we must all make mosquito bite prevention a habit. WNV does not blanket the state, but occurs in ‘hot spots’ where conditions are just right,” said Pue. “Though people may hear that WNV was found in another part of the state, that doesn’t mean everyone else is safe; WNV can be anywhere, so prevention is important everywhere.”


Pue said the number of human WNV cases saw a steady decline from 2002 through 2005, but there has been a steady increase in cases since then. He said the increase in cases shows that WNV is unpredictable, it can show up anywhere in the state, and that people need to stay alert and not let down their guard.

The best ways to prevent infection are using an effective insect repellent containing DEET or picaridin before going outside to work or play, especially in the morning and evening (mosquitoes’ most active feeding times). People should also make sure homes, properties, and communities are protected by cleaning up junk, trash, and other things that can hold water and become breeding grounds for mosquitoes that can carry WNV.

It also helps to wear long sleeve shirts and pants when outdoors to cover the skin. Some people may want to consider staying indoors at dawn, dusk, and in the early evening, which are peak mosquito biting times. Pue added that homes should be mosquito-proofed by ensuring doors and windows have screens, and standing water that can serve as mosquito breeding habitat should be eliminated.

Most people infected with the West Nile virus do not develop any symptoms. Sometimes, though, a flu-like illness results one-to-two weeks after exposure with symptoms such as fever, headache, body aches, skin rash, and swollen lymph nodes. Less than one percent of infected people may develop a serious illness that includes encephalitis (inflammation of the brain). These people might experience headache, high fever, neck stiffness, disorientation, convulsions, and muscle weakness. Infection may prove fatal, especially among the elderly, in a small number of those who develop encephalitis. West Nile virus is not transmitted directly from birds to humans or from person to person.

Medical care should be sought as soon as possible for people who have symptoms suggesting severe illness. There is no specific treatment for West Nile infection or vaccine to prevent it. Treatment of severe illnesses includes hospitalization, use of intravenous fluids and nutrition, respiratory support, prevention of secondary infections, and good nursing care.

Because West Nile virus can infect many bird species and some game animals, hunters should follow the usual precautions when handling wild animals. They should wear gloves when handling and cleaning animals to prevent blood exposure to bare hands and meat should be thoroughly cooked.


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