West Nile Virus Surveillance Outlined

The Michigan Department of Community Health, Michigan Department of Agriculture, Michigan Department of Natural Resources and Michigan State University today outlined the cooperative efforts in the West Nile virus statewide surveillance.

"Michigan has had an aggressive surveillance system in place for West Nile virus since this mosquito-carried virus was first identified in North America in 1999," said Michigan Department of Community Health Director James K. Haveman, Jr.

"This cooperative effort among the agencies involved has allowed us to be pro-active in looking for any evidence of the virus in Michigan," said Michigan Department of Agriculture Director Dan Wyant.

The system includes:

Human surveillance. The Department of Community Health works closely with physicians, infection control practitioners, hospital epidemiologists, laboratory directors and local health departments to identify any possible cases of the virus in Michigan.

Surveillance of horses. The Department of Agriculture works closely with private veterinarians, Michigan State University and horse owners to detect cases of encephalitis including West Nile virus in horses. If a horse is infected with the virus, there is no risk for that horse to directly transmit the virus to other animals or humans.

Surveillance of crows. In 1999, a connection was made between an outbreak of human West Nile virus infection and disease in birds, especially in American crows in the New York City area. The most sensitive indicator of West Nile virus activity in an area is the presence of dead crows, which is why the Michigan Department of Agriculture, the Department of Natural Resources, local health departments and animal control offices are partners in crow surveillance throughout the state. Crows submitted are sent to the Animal Health Diagnostic Laboratory at Michigan State University for testing.

Mosquito surveillance. The Michigan Department of Agriculture works cooperatively with Michigan State University, local health departments and mosquito control programs throughout the state in an ongoing assessment of mosquito populations. This includes testing mosquitos for West Nile virus.

Laboratory efforts. The Michigan Department of Community Health received a $90,000 grant from the Centers for Disease Control and Prevention (CDC) to increase the state's epidemiology and laboratory capacity to conduct surveillance for West Nile virus. These funds have been used to expand specimen collection and testing services at the Departments of Community Health and Agriculture and at Michigan State University.

Health Care Provider education. Efforts to educate the medical community about the West Nile virus have been ongoing and will continue to assist neurologists, infectious disease doctors and emergency room providers to identify and treat individuals.

Public Education Campaign. The partners have developed a website with important information about the West Nile virus and precautions that individuals should take to protect themselves and their families from the risk of the virus. The site can be found at http://www.mda.state.mi.us and by clicking on "West Nile Virus." Education information can also be obtained by calling the West Nile virus toll free hotline at 1-888-668-0869.

Mosquitoes become infected with West Nile virus when they feed on infected birds that carry the virus in their blood. After 10 to 14 days, the mosquitos salivary glands become infected and those infected mosquitoes can then transmit the virus to humans and other animals while biting them to take blood. During blood feeding, the mosquito injects the virus into the animal or human, where it multiplies and may cause illness.

Most crows are very susceptible to infection with West Nile virus and will die within 2-3 weeks of infection. However, most people infected with the West Nile virus have no symptoms of illness, but some may become ill three to 15 days after the bite of an infected mosquito. Based on preliminary evidence, about one in four infected persons will have mild illness with fever, headache and body aches, sometimes with skin rash and swollen lymph glands. A more severe infection, encephalitis, is less common and may be marked by headache, high fever, stiff neck, stupor, disorientation, coma, tremors, convulsions, muscle weakness and paralysis. In a few cases, mostly among the elderly, death may occur.

The risk of West Nile encephalitis is limited to persons in areas where virus is detected and is higher in persons 50 years of age and older. A 1999 survey of residents in the most affected area of New York City showed that about 2.6% of residents had been infected with West Nile virus, but either were not clinically ill or had only a mild illness.

The virus is NOT transmitted from person to person, horse to horse or horse to person. You cannot get the virus from touching or kissing a person who has the disease, from a health care worker who has treated someone with the disease or from contact with an infected horse.

While there is no vaccine for West Nile encephalitis, there are many ways to reduce the risk of becoming infected. They include:

Apply insect repellent that contains the active ingredient DEET to exposed skin. Follow the manufacturer's directions for use on the label.

Spray clothing with repellents containing permethrin or DEET because mosquitoes may bite through thin clothing. Follow the manufacturer's directions for use on the label. Vitamin B and "ultrasonic" devices are NOT effective in preventing mosquito bites.

Avoid applying repellent to children under 2 years of age, and to the hands of older children because repellents may irritate the eyes and mouth.

Maintain window and door screening to keep mosquitoes out of buildings.

Drain standing water in the yard. Empty water from mosquito breeding sites, such as flower pots, pet bowls, clogged rain gutters, swimming pool covers, discarded tires, buckets, barrels, cans and similar sites in which mosquitoes can lay eggs.

Wear long-sleeved shirts and long pants when outdoors.