D.C. health authorities have positively identified the West Nile Virus in several mosquito samples in the District and are urging residents to eliminate mosquito breeding sites by emptying standing water from flower pots, buckets and barrels and to use insect repellent.

West Nile virus is mainly an infection of birds, but an infected mosquito can spread it to humans. The virus has been found in other mosquito samples around the region. But so far, no human cases have been reported. Typically, most West Nile infections are reported in August and September.

But health officials say the mild winter, early spring and very hot summer have fostered more breeding. More serious illnesses from West Nile virus have been reported so far this year than any since 2004, according to the federal Centers for Disease Control and Prevention.

About one in five infected people get sick with fever, headache and other mild symptoms. One in 150 people will develop serious symptoms including high fever, neck stiffness, disorientation, coma and paralysis. The elderly and those with weak immune citizens are more vulnerable to infection.