The southwestern US state of Texas is battling an outbreak of the West Nile virus, with 17 deaths blamed on the mosquito-borne disease, authorities said Wednesday.
Throughout the state 465 people have been sickened since the start of the year, putting it on track to have the most cases since the disease first emerged a decade ago, the Texas Department of State Health Services said.
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 that has caused, and appears likely to continue to cause, widespread and severe illness and loss of life," Mayor Michael Rawlings said in a proclamation of emergency that took effect Wednesday.
The virus has claimed ten lives in the county so far, local and state health authorities said.
First discovered in Uganda in 1937, the virus is carried by birds and spread to humans by mosquitoes.
Severe symptoms of the virus include high fever, vision loss and paralysis, while milder symptoms range from headaches to skin rashes.
At least 693 cases -- both confirmed and probable -- of the virus have been reported in the United States this year, including 26 deaths, according to the Centers for Disease Control and Prevention.
Texas tops the list in both total cases and fatalities.
In 2011, Texas saw a total of 27 cases and two deaths, the CDC said. Across the United States, 712 confirmed and probable cases and 43 fatalities were reported over that same 12-month period.
The worst year on record in Texas was 2003, with 40 deaths related to the West Nile virus, said Christine Mann, a spokeswoman for the Texas Department of State Health Services.
Mann told AFP that the outbreak could be linked to a mild winter and rainy spring in the state. "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.