West Nile Virus confirmed in Md.; help reduce mosquito breeding sites to prevent WNV, Zika

Dr. Howard Haft, during a recent meeting at the Somerset County Health Dept.

Dr. Howard Haft, during a recent meeting at the Somerset County Health Dept.

BALTIMORE — The Department of Health and Mental Hygiene is announcing the first confirmed case of West Nile Virus (WNV) in Maryland this year. The patient, an adult who lives in Western Maryland, survived the infection.


In addition, WNV has been detected in mosquito pools collected in Montgomery and Prince George’s counties. A mosquito pool is a group of mosquitoes collected at one of several trap sites across the state. Eastern equine encephalitis (EEE), a related mosquito-borne disease, also has been detected in mosquitoes on the Eastern Shore.


“A case of WNV is expected around this time of year,” said Deputy Secretary of Public Health Services Dr. Howard Haft. “Marylanders are reminded that they can take simple steps to reduce the risk of mosquito bites, since mosquitoes can spread such infections as WNV and Zika.” Those protective measures include:

  • Avoiding areas of high mosquito activity.
  • Wearing long pants, long-sleeved shirts and hats, when concerned about mosquitoes.
  • Using an EPA-registered insect repellent according to package directions.

Most individuals infected with WNV will not have any symptoms. People that do develop illness usually will have any combination of fever, headache, body aches, skin rash and swollen lymph glands. These symptoms generally appear two to 14 days following the bite of an infected mosquito. Fewer than 1 percent of people exposed to the virus will develop more severe infections, with symptoms such as headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness and paralysis. In rare instances, WNV can be fatal.


People older than 60 have the greatest risk of developing severe disease. People with compromised immune systems also may be at high risk for WNV infection.


The number of human WNV cases in Maryland has varied over time. The peak years of human activity were 2003 and 2012, with 73 and 47 WNV cases reported statewide, respectively. In 2015, there were 46 human cases of WNV infection in Maryland, nearly reaching the 2012 peak.


West Nile Virus is not to be confused with the Zika virus.  Although both viruses are carried by mosquitoes, Zika symptoms – when experienced at all – are usually marked by a combination of fever, conjunctivitis, joint pain and rash that present about 10 days after the bite of an infected mosquito.  Pregnant women and their fetuses are of primary concern with Zika infection, as this virus has been observed to cause fetal abnormalities.


Residents are urged to monitor their own yards and gardens for standing water that can serve as a breeding ground for mosquitoes that may carry WNV or Zika. Although the mosquitos that carry WNV are different from those that carry Zika, they both breed in and around standing water.  Even small amounts of water in a discarded can or container will support dozens of mosquitoes. To eliminate mosquito-breeding areas and lessen the risk of virus transmission:

  • Clean rain gutters to allow water to flow freely.
  • Empty or screen corrugated drain pipes.
  • Remove old tires or drill drainage holes in tires used as playground equipment.
  • Turn over wading pools, wheelbarrows, wagons and carts when not in use. Flush water from the bottom of plant holders twice a week.
  • Replace water in birdbaths at least twice a week.
  • Turn garbage can lids upside down and make sure trash receptacles are empty of water.
  • Fix dripping faucets.
  • Aerate ornamental pools and water gardens or stock with fish and use a circulating filter system.

Although birds are not routinely tested for WNV in Maryland, sick or injured birds can be reported to an appropriate local wildlife rehabilitator. Residents can call 1-877-463-6497 for a list of licensed rehabilitators or visit the Maryland Department of Natural Resources web site at http://goo.gl/KPXXaX. Detailed instructions on what to do when you find a sick or dead bird can be found at http://goo.gl/297cZW.  Health and Mental Hygiene provides weekly updates of WNV detected in humans, mosquitoes and horses in Maryland on its website. The reports also will be available each Thursday at http://goo.gl/297cZW. In addition to this, find additional information on West Nile virus and other mosquito-borne diseases at the Maryland Department of Agriculture and the U.S. Centers for Disease Control and Prevention.

The Somerset County Health Department's mission is to promote healthy families in healthy communities. Find out more by visiting SomersetHealth.org.

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