West Nile Virus

Quick Contact Numbers

Division Number
General Services 410-535-1600, ext. 2327
Mosquito Control  410-535-6924
Public Works Main Line 410-535-2204 or 410-535-2205


West Nile Encephalitis is an infection of the brain caused by the West Nile Virus (WNV) transmitted by mosquitoes. It was discovered in New York City in September of 1999. Since that time dead birds containing the virus have been collected in most of the continental states, including Maryland. It is not known where the virus originated in the United States, but it is closely related to strains in the Middle East. There is no vaccine against WNV; however, the chance for severe illness is very low.

Previous Findings

In 2002, the Maryland Department of Health and Mental Hygiene determined that a total of 14 birds out of 141 submitted from Calvert County were positive. The Department of Health has decided that dead birds will not be collected anymore, since West Nile Virus is endemic to the county.

Again in 2003, West Nile Virus appeared in Maryland and became nightly news segments for most of the year. WNV was found in the horse population for the first time in Calvert County, but there were no documented human cases. Two horses were destroyed after contracting the disease.


The Calvert County Mosquito Control Program recommends that you have your horse vaccinated against WNV. An additional booster shot during the mid-summer, when the risk for contracting WNV is highest, is recommended. Horse owners should discuss this with their veterinarians for more information.

Tips to Avoid Mosquito Bites and Minimize the Risk of Disease

  • Avoid areas of high mosquito infestation
  • Avoid unnecessary outdoor activities at dawn and dusk when mosquitoes are most active
  • Drain all water-holding outdoor containers around the home
  • Inspect basements and crawl spaces for flooding; if necessary, drain immediately
  • Restrict the outdoor play of your children if mosquitoes are present
  • The very young, the elderly and persons with depressed immune systems are at most risk for acquiring disease from mosquito bites
  • Use mosquito repellants according to product label directions
  • Wear long pants, long-sleeve shirt and hat when outdoors

Learn more about West Nile Virus