Aircraft have begun spraying pesticide over parts of Dallas, Texas to combat an outbreak of mosquito-borne West Nile Virus blamed for 17 deaths this year, authorities said Friday.
The Texas Department of State Health Services said the aircraft covered 52,000 acres of Dallas County on Thursday night, opening a new front to stop the spread of West Nile Virus.
"Aerial spraying is a safe and very effective tool, but it doesn't take the place of the basic precautions," said David Lakey, the head of the health department.
"We are urging people to continue using insect repellent every time they go outside."
Four more aircraft were to resume spraying later Friday, and residents were cautioned to avoid going outdoors, keep pets inside, cover ornamental fishponds and rinse off homegrown fruits and vegetables.
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 department 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 on Wednesday.
"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.
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.