Missouri Department of Health & Senior Services
P.O. Box 570
Jefferson City, Mo. 65109

May 27, 2004

Dr. Howard Pue
Karen Yates
Section for Communicable Disease Prevention
Telephone: 573-751-6113

State Prepares for Return of West Nile Virus

The Missouri Department of Health and Senior Services (DHSS) today urged Missourians to prepare for the return of West Nile virus (WNV). This year will mark the fourth year for the virus in Missouri and the sixth year for its presence in the United States. To date this year, no human cases have been reported in Missouri.

"Although WNV infection has not been confirmed in any species in Missouri so far this year, we expect that to change before too long," said Howard Pue, State Public Health Veterinarian. "Some nearby states have already reported WNV activity. For example, Illinois and Oklahoma recently detected WNV-positive crows. This is especially significant, since these two states did not report avian activity last year until June and July, respectively."

"West Nile virus will continue to spread across the country until it reaches the Pacific Ocean, but some infected birds and mosquitoes have remained in Missouri," said Pue. "DHSS, local public health agencies, and other partners conduct surveillance for West Nile virus infection in people, birds, mosquitoes, and horses. Results of this surveillance are used to determine the location and level of West Nile virus activity in the state and to assess the public health risk," Pue added.

In 2003, Missouri's first WNV activity in non-human species began in mid to late June. The first human case in each of the past two years had an onset date of July 31. In 2002, 168 Missourians were diagnosed with WNV disease; seven of these people died. In 2003, there were 64 human cases with eight fatalities.

West Nile virus, like most mosquito-borne viruses, is found in wild and domestic birds. When a mosquito feeds on an infected bird, it can pick up the virus and transmit it to noninfected birds. Many of these birds die. Occasionally, infected mosquitoes will feed on mammals such as horses and humans, and transmit the virus to them.

People who observe an unusual number of dead birds, especially crows, blue jays, and birds of prey are encouraged to report the incident to their city or county health department. Health officials will determine whether the event should be investigated and whether bird specimens should be submitted to a laboratory for testing. There are many things that can kill birds besides this virus, and therefore not all dead-bird sightings are investigated.

Most people infected with West Nile virus do not develop any symptoms. Sometimes, though, mild 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 persons might experience severe headache, high fever, neck stiffness, disorientation, convulsions, and muscle weakness.

Infection may prove fatal in a small number of those who develop encephalitis. Although any person can develop serious disease as a result of WNV infection, persons over 50 years of age are at highest risk. West Nile virus is not transmitted directly from birds to humans nor from person-to-person.

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

"Missourians should not be afraid to go outdoors and enjoy summertime activities, but there are some simple precautions they should take to help avoid infection," said Karen Yates, Vector-borne Disease Program Coordinator. "To prevent West Nile virus infection people should focus on personal protection and protection around the home. People should take extra precautions at dawn and dusk when mosquitoes are most active; wear protective clothing such as pants and long-sleeved shirts when practical; and, apply insect repellents containing DEET to clothing and exposed skin -- always follow label directions when applying repellents. People should also ensure doors and windows have screens that are in good repair. To reduce mosquito breeding areas around houses and property, people should eliminate standing water from flowerpots, barrels, used tires, clogged gutters, and other places where mosquitoes can breed; and, change water regularly in birdbaths, pet bowls, and wading pools."

"It's especially important to eliminate standing water from around the home, since mosquitoes that carry West Nile virus do not travel very far from where they breed to find a blood meal," Yates said. "If mosquitoes are biting you, there's a good chance you are unknowingly breeding them yourself. It's a classic case of they bite the hand that 'breeds' them," Yates added.

As in 2003, DHSS will list human cases on its WNV web site as they occur. The privacy of infected individuals will be protected by the public release of only limited demographic information -- the gender, age, and county of residence of each case. Only major developments in Missouri's West Nile virus situation will be announced through news releases, including any deaths related to the virus. Human case data posted on the web site represent cases that are under investigation and are therefore provisional.

For more information on West Nile virus, contact your local health department or the Department of Health and Senior Services at 1-866/628-9891 or 573/751-6113. Attached is a fact sheet on West Nile virus. For more information, go to the Missouri Department of Health and Senior Services web site at http://www.dhss.mo.gov/WestNileVirus.

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