A 70-year-old woman contracted the District's first case of West Nile virus in 2012, a hospital spokeswoman said.

Hours after the D.C. Department of Health announced that authorities had detected West Nile in mosquito samples around the city, Sibley Memorial Hospital confirmed that it had treated a woman whom physicians diagnosed with a mild case.

"A 70-year-old female was hospitalized at Sibley Memorial Hospital for three days in early August," spokeswoman Sheliah Roy said. "The patient received a diagnosis of West Nile virus, received treatment, fully recovered and was released."

Although the woman's diagnosis was the first in the District this year, the virus had already appeared in the Mid-Atlantic region. So far in 2012, Maryland authorities have reported nine West Nile cases, and Virginia officials said two people in their state have been diagnosed.

West Nile is a mosquito-borne virus that can prompt an array of symptoms including diarrhea, nausea and fever. In extreme cases, the virus results in meningitis-like symptoms such as a stiff neck or muscle weakness.

About 10 percent of patients who contract a severe strain of West Nile do not survive, federal health officials say.

CDC records show that the District has reported an infection in a human every year since 2008. Last year, the city said 15 people were infected, accounting for a small part of the 715 cases nationwide.

In 2002, the District recorded 34 West Nile infections, the most ever in the city since the virus first surfaced in the United States in 1999.