The US state of Texas is battling an outbreak of the West Nile virus, with 17 deaths being blamed on the mosquito-borne disease, authorities said Wednesday.
Throughout the state, 381 people have been sickened since the start of the year, according to the Texas Department of State Health Services.
"Texas is on track to have the most cases of West Nile illness since the disease first emerged in the state in 2002," it said in a statement.
The county incorporating Dallas, the ninth-largest city in the United States, has been the hardest hit, prompting the mayor to declare a local state of disaster.
"The City of Dallas is experiencing a widespread outbreak of mosquito-borne West Nile virus and has caused and appears likely to continue to cause widespread and severe illness and loss of life," Mayor Michael Rawlings said in the proclamation of emergency that takes effect Wednesday.
The virus has claimed ten lives in the county so far, local health authorities said. State officials put the toll at nine.
First discovered in Uganda in 1937, the virus is carried by birds and spread to humans by mosquitoes.
Severe symptoms can include high fever, vision loss and paralysis, while milder manifestations of the virus can range from headaches to skin rashes.
According to the Centers for Disease Control and Prevention, as of Tuesday 693 cases -- both confirmed and probable -- of the virus have been reported country-wide so far this year, including 26 deaths. Texas tops the list of both cases and fatalities.
In 2011, Texas saw a total of 27 cases and two deaths, the CDC said. Country-wide, 712 confirmed and probable cases and 43 fatalities were reported over that 12-month period.
Christine Mann, a spokeswoman for the Texas Department of State Health Services, told AFP that the outbreak could be linked to a mild winter and rainy spring in the state.
But "it's really not clear at this point," she said.
In an effort to stem the number of new infections, Texas authorities have urged residents to use insect repellent before heading outdoors, remain inside at dusk and at dawn, dress in protective clothing and drain standing water that could become a breeding ground for mosquitoes.
Last month, officials in New York City said the West Nile virus had been detected on Staten Island, one of the city's five boroughs.