Baltimore, Anne Arundel and Prince George's counties are getting sprayed for mosquitoes and health officials are warning residents to take precautions as the nation copes with the worst season of West Nile Virus since the disease was discovered in the United States in 1999.

One person in Maryland has died from the disease this summer and 21 have contracted it, according to the Maryland Department of Health and Mental Hygiene.

Nationally, the potentially fatal disease, spread by mosquitoes that pick it up from infected birds, has afflicted 1,993 people, according to the Centers for Disease Control. Nearly every state has been affected. The number of cases leapt 25 percent last week and there's still roughly a month to go in mosquito season.