Two West Nile-related deaths were confirmed Tuesday 2,000 miles apart - the 11th confirmed this year in Dallas County, Texas, and the first in Fresno County, Calif.
Nationwide, there have been at least 26 deaths attributed to the West Nile virus this year, according to the Centers for Disease Control and Prevention.
The Fresno County Department of Public Health said an elderly woman was hospitalized for the virus and later died, marking the second West Nile-related death in California in 2012.
"All residents, especially those over 50 years of age and those with chronic health conditions, must take this disease seriously and should take every precaution to protect themselves and their families from mosquito bites," said Dr. Edward L. Moreno, director and health officer for the Fresno County Department of Public Health, in a news release. "I also encourage residents to engage the services of their mosquito abatement district, if necessary, to eliminate possible mosquito-breeding sources around their homes."
Dallas County Health and Human Services spokeswoman Patricia Huston would not provide any specific identifying information on the county's 11th virus fatality because of medical confidentiality and personal privacy rules.
The death came just a day after Dallas launched a second aerial attack against the West Nile virus. Five small planes sprayed more than 360,000 acres with mosquito-killing pesticides.
The first aerial attack was last Friday, making it the first time in more than 40 years that Dallas County has used an aerial launch to treat a virus.
"What our preliminary data is showing is that the aerial planes that are going out are knocking down these mosquitoes," DCHHS director Zachary Thompson told ABC News affiliate WFAA.
The DCHHS is testing mosquito traps set around the city to see how much the insecticides have affected the West Nile mosquito population, Thompson added.
The insecticide aerial fight came on the cusp of the worst nationwide outbreak of the West Nile virus, which has now killed 11 people in Dallas alone and sickened more than 200.
The Centers for Disease Control and Prevention has reported 693 cases in 43 states, with the majority of infections in Texas. Oklahoma, which borders Texas to the north, has reported more than 100 cases, three of which have resulted in death.
According to the CDC, up to 20 percent of infected people develop West Nile fever and exhibit mild symptoms - including fever, headache, muscle weakness, nausea and vomiting. They might also develop swollen lymph glands and a rash on the chest, back or stomach. Symptoms can last for as little as a few days, though even healthy people have become sick for several weeks.
On average, about 4 out of 5 people who are infected with the West Nile virus will not show any symptoms at all.
There is no specific treatment for a West Nile virus infection. In cases with milder symptoms, people experience symptoms such as fever and aches that pass on their own.
There is no known cure for the virus, however there are preventative measures. DCHHS said the best way to avoid exposure to West Nile virus is to practice the four Ds: