West Nile Virus Precautions Important to Remember

May 20, 2002


Michigan Department of Community Health Director James K. Haveman, Jr., and Michigan Department of Agriculture Director Dan Wyant, today reminded citizens of what they can do to protect themselves from mosquito-borne illnesses such as West Nile virus.  West Nile virus was detected for the first time in mosquitoes and birds in Michigan in 2001. 

"Although there have been no cases of West Nile Virus detected yet this year in mosquitoes, birds, horses or humans in Michigan, we will again see evidence of West Nile virus activity in our state," said Haveman.  "By raising awareness of what people can do to minimize exposure to mosquitoes, we can reduce potential exposure."

"Based upon last year's aggressive testing, surveillance and outreach efforts, we know that it is important for Michigan residents to take an active role in identifying and eliminating potential mosquito breeding sites in and around their homes, barns and stables to help reduce West Nile exposure risks for people and horses," said Wyant.

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 mosquitoes 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.  Crows are very susceptible to infection with West Nile virus and will die within two to three weeks of infection.  Because of this, dead crows are the most sensitive indicator for the presence of West Nile virus in an area.

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.  Encephalitis is less common and may include 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 virus is NOT transmitted from person-to-person.  You cannot get it from touching or kissing a person who has the virus or from a health care worker who has treated someone with it.  While there is no human vaccine for West Nile encephalitis, there are many ways to reduce the risk of becoming infected.  They include:

  • Applying insect repellent that contains the active ingredient DEET to exposed skin or clothing, always following the manufacturer=s directions for use on the label.
  • Avoid applying repellent to children under 2 years of age, and to the hands of older children because repellents may be transferred to the eyes or mouth potentially causing irritation or adverse health effects.
  • Maintaining window and door screening to keep mosquitoes out of buildings.
  • Draining 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. 
  • Wearing long-sleeved shirts and long pants when outdoors.

Horse owners are encouraged to contact their local veterinarian to discuss appropriate preventive measures.  Prevention tips for horses include:

  • Using approved insect repellants to protect horses.
  • Placing horses in stables, stalls or barns during the prime mosquito exposure hours of dawn and dusk, and other times when mosquitoes are present, if possible.
  • Eliminate standing water and drain troughs and buckets at least two times a week.
  • Consulting with local veterinarian about using the now available approved vaccine to help control this disease in horses.  While it has been shown safe for use, effectiveness has not yet been proven.

The Michigan Departments of Community Health, Agriculture, and Natural Resources, Michigan State University Animal Health Diagnostic Laboratory and Michigan State University Department of Entomology have all worked cooperatively on surveillance activities for West Nile Virus in Michigan.  The system includes:

Human surveillance.  The Department of Community Health will continue to work closely with physicians, infection control practitioners, hospital epidemiologists, local health departments and laboratory directors to identify possible cases of human disease in Michigan.  This active surveillance will enhance rapid detection of possible cases.


Surveillance of crows.  The most sensitive indicator of West Nile virus activity in an area is the presence of dead crows.  Timely reporting of dead crows can be made to the West Nile Virus toll-free hotline at 1-888-668-0869 or through a website being piloted by Michigan State University that can be accessed through www.michigan.gov/mda and by clicking on "West Nile Virus" and "2002 Specimen Collection and Submission Instructions."  Selected crows will be sent to the Animal Health Diagnostic Laboratory at Michigan State University for testing.  Persons should always avoid barehanded contact with dead birds by using gloves or by grabbing the dead crow with a plastic grocery bag. 

Surveillance of horses.  The Department of Agriculture will continue to work 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.

Mosquito surveillance.  The Michigan Department of Agriculture will coordinate an educational workshop to provide information for local health departments regarding source reduction, personal protection and mosquito collection and identification.  The Department of Agriculture will partner with other state and local agencies to carry out this workshop. 


Laboratory efforts.  The Michigan Department of Community Health has increased epidemiology and laboratory capacity to conduct surveillance for West Nile virus.  The laboratory has Biosafety Level 3 facilities and appropriate training from the Centers for Disease Control and Prevention to enhance existing capacity to detect West Nile and other mosquito-borne viruses. 


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


Information on West Nile virus can be found at http://www.michigan.gov/mda, http://www.cdc.gov or by calling the West Nile virus toll free hotline at 888-668-0869.