The West Nile virus, responsible for more than 60 deaths in the United States so far this year, has now claimed its first victim in the eastern state of Maryland, state health officials said Thursday.
"We reported 13 cases of West Nile virus that occurred since the 1st of July," a spokeswoman for the state health department, Dori Henry, told AFP.
Between 2001 and 2011, 20 people died of the virus in Maryland, out of a total of 215 infected.
So far this year, the virus has killed 66 people across the country, out of a total of 1,590 infected.
It is the worst outbreak of the mosquito-borne disease since it was first detected in the United States in 1999, according to the Centers for Disease Control (CDC).
The CDC says more than 70 percent of infections were reported in only six states—Texas, Mississippi, Louisiana, Oklahoma, Michigan and South Dakota.
Texas alone has seen 45 percent of the cases reported nationwide.
But nearly all of the country has been hit by the virus, which is more prevalent in the summer months when mosquitoes are most active. Forty-eight states have reported cases.
Authorities in New York City announced Tuesday that several neighborhoods would be sprayed with pesticide to combat the spread of the virus.
The record number of cases registered in 2012 could be due to a relatively mild winter, an early spring and hot summer, according to the CDC.
Other factors potentially contributing to the outbreak are birds transporting the virus—first identified in Uganda in 1937—and the exploding mosquito population.
About one in 150 people infected will develop severe illness with symptoms that include high fever, convulsions, vision loss, numbness, coma and can cause permanent paralysis and neurological damage.
Eighty percent of those infected will not show any symptoms at all and milder symptoms range from headaches to skin rashes, the CDC said.