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Division of Infectious Diseases

Help Control West Nile Virus in Illinois
By: Dr. Nancy Khardori

MosquitoWest Nile virus was initially isolated in 1937 from the blood of a woman in the West Nile district of Uganda. It was mainly confined to the eastern Hemisphere until 1999 when it was first reported in New York City. Since then it has been gradually spreading throughout the country.

In 2002 there were more than 4, 002 cases of West Nile virus and more than 260 deaths in the United States. Illinois, with more than 800 human cases and 62 deaths had the unfortunate distinction of leading the nation.

West Nile virus is a single stranded RNA virus. It belongs to Japanese encephalitis virus serocomplex, which contains several viruses associated with human encephalitis. West Nile virus is maintained in a cycle involving mosquitoes and birds, and human infection occurs with mosquito bites.

West Nile virus can cause severe neurological disease, which is an uncommon although a potentially fatal complication of the infection. Encephalitis is the common neurological presentation although patients can also present other symptoms. Encephalitis is an inflammation of the brain, which can be caused by many viruses. It manifests as fever, confusion, drowsiness, irritability, worsening consciousness and memory loss.

Peak incidence of the West Nile virus is in late August and early September. Incubation period ranges from three to 14 days. Most human infections are clinically without any symptoms.

Common symptoms are malaise, low-grade fever, anorexia, nausea, vomiting, achy muscles, rash and swelling of the lymph nodes. These symptoms usually last for three to six days. Neurological symptoms develop in one in 150 patients. Meningitis, encephalitis (more common) or both may occur. Reversible Parkinsonism features can occur. We have reported two cases of reversible Parkinsonism due to West Nile virus from Central Illinois.

Prevention of mosquito bites is the main strategy. Use mosquito repellents and mosquito proof your home. Elimination of standing water, which can serve as breeding sites for mosquitoes, is very important. In addition, agents like Bacillus thuringiensis, Bacillus sphaericus and methoprene can kill the larvae before they mature into adult mosquitoes.

EPA approved organophosphates or pyrethroids are used for ground or aerial spraying. DEET 10-50 percent can be used on skin, clothing, pets, tents and screens. Only 10 DEET can be used for children except infants. Permerthrin is also a mosquito repellent, but it can only be used on clothing, tents and nets. Be careful not to place repellents on the face and hands of children.

Live attenuated recombinant vaccine is under development. Until the vaccine is developed treatment is mainly supportive care once the disease occurs. Ribavirin and Interferon alpha 2b have been shown to be effective in the laboratory. No controlled trials are available on the effectiveness of these agents, steroids, anti-seizure medications or osmotic agents in the treatment of West Nile virus infection.

There is no specific treatment for West Nile virus infection except supportive care. In severe cases of Encephalitis, intensive care of respiratory and cardiac status plays a major role.

You can help reduce the number of mosquitoes by draining sources of standing water. At least once or twice a week, empty water from flower pots, pet food and water dishes, birdbaths, swimming pool covers, buckets, barrels and cans. Check for clogged rain gutters. Remove discarded tires and other items that could collect water.

Detailed information about West Nile virus can be viewed at Centers for Disease Control (CDC) Web site www.cdc.gov/ncidod/dvbid/westnile and the Illinois Department of Public Health Web site www.idph.state.il.us/envhealth/wnv.htm.

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