The West Nile virus has spread to Texas, Oklahoma and Nebraska — the farthest west it has been found — prompting officials to begin spraying creeks, ponds and anywhere there is standing water to eradicate mosquitoes that carry the deadly virus.
Mosquitoes hovered near Joyce Hopkins' heavily wooded Dallas home Thursday as a dead blue jay she found in her driveway was bagged and taken away for testing by health officials.
"I just think what you do is take responsible precautions," said Hopkins, who uses bug repellent and zappers.
As the virus marches west across the United States, health officials say people should be cautious, but not overly concerned.
Less than 1 percent of the mosquitoes where the virus has been found carry it, and less than 1 percent of bites from those cause serious illness, said Doug McBride, a spokesman for the Texas Department of Health.
From its discovery in 1999 in New York City, the virus has infected at least 149 people and killed at least 18 nationwide, according to the Centers for Disease Control and Prevention.
Cases have been recorded in 31 states and the District of Columbia; Texas, Oklahoma, Nebraska and North Dakota were added to the list this year, according to the CDC.
Mosquitoes contract the virus from birds and pass it to humans and horses. In Texas, 50 birds and eight horses have tested positive, but no human cases have been found, McBride said.
In Tulsa, Okla., a dead crow found last week tested positive late Wednesday. Officials there increased daily sprayings of insecticides from two trucks to three, and residents were asked to mow lawns and empty any pools of standing water.
There were no efforts under way in Nebraska to spray pesticides or drain standing water after the state's first case was confirmed this week from a dead blue jay found June 28, officials said.
But Nebraska officials said they were stepping up tracking efforts.
About a dozen lighted mosquito traps, baited with dry ice to attract the insects with carbon dioxide, were placed in a Lincoln neighborhood. Other tracking sites around Nebraska have flocks of sentinel chickens which are tested biweekly for the disease.
Just this week, the CDC confirmed four new cases of the mosquito-borne virus in Louisiana, bringing the number to seven this year. The nation's first human cases reported this year were in Louisiana.
The virus causes flu-like symptoms and, in about 1 percent of human cases, can cause a serious illness that includes encephalitis, an inflammation of the brain. McBride said as with most illnesses, the young, the elderly and those with weak immune systems are the most vulnerable.
No vaccine exists for humans, though health officials say a vaccine for horses, while not fully tested, has shown promise.
Experts say the best weapon against the disease is reducing the likelihood of mosquito bites, such as wearing mosquito repellent and long pants and sleeves and emptying standing water near homes.