WASHINGTON (AP). - The city of Dallas started spraying the metropolitan area  with pesticides to eliminate the worst outbreak of the West Nile virus in the U.S., and has already infected nearly 700 people across the country. 

Dallas County has already reported 217 cases of the potentially deadly disease transmitted by mosquitoes, while so far the entire state of Texas total 336, according to figures from the Centers for Disease Control and Prevention (CDC). The mayor of Dallas, Mike Rawlings, yesterday signed an emergency declaration to begin spraying due to the spread of the virus which has killed at least 14 people in this state and of 26 nationwide.

America is suffering the largest numbers of registered cases of the virus since the first register in 1999, with 693 reported nationwide during 2012 over 32 states.

Of reported infections, 80 percent have been in the states of Texas, Mississippi and Oklahoma, according to the CDC.

Symptoms include fever, headache, body aches, joint pains, vomiting, diarrhea or rashes, and less than 1% of cases develop the disease at its most serious, including encephalitis or meningitis (inflammation of the brain or surrounding tissues), the CDC said.

Health officials remind people most at risk are those above 50 years of age who have suffered diseases such as cancer, diabetes or kidney disease, as well as those who have undergone organ transplants.

There are no medications to treat West Nile virus nor vaccines to prevent infection, and those with milder disease recover themselves.

Health experts say that preventive measures include avoiding mosquito bites, use repellent and get rid of the breeding of insects. EFE