The country is suffering from the worst West Nile virus outbreaks on record and the number of cases is still growing. The overwhelming majority of the cases are in Texas.
There have been more than 1,100 human cases of West Nile virus in 38 states and more than 40 deaths. Twenty-nine of those deaths are in Texas, including three in Houston and one in Wharton County.
For every one reported case, dozens of others may be infected and exhibit few to no symptoms.
Doctors said for every 150 people who have West Nile virus, only one is severe. The average person will feel bad and have flu-like symptoms, but they'll recover rather easily.
Doctors in the Houston area are fielding a lot of questions about West Nile virus.
Half of the cases in the recent West Nile virus outbreak are in Texas, according to the Centers for Disease Control and Prevention.
Kelsey-Seybold Clinics across the city are getting a lot of calls from worried people.
"It's all ages – parents calling for their children and adult patients asking about their own selves," Dr. Nicholas Solomos said.
The most vulnerable people are the elderly. Of the 19 reported cases in Houston and Harris County, nine of the people diagnosed were over the age of 55.
University of Texas health experts in the Texas Medical Centers aid more people are being tested for West Nile virus as they come in with fever.
"There are different tests you can do – a spinal fluid, a lumbar puncture – to see if the patient has meningitis or encephalitis. Then you can test the spinal fluid or the serum for antibodies against West Nile," Dr. Rodrigo Hasbun with UT Helath-Memorial Hermann said.
It can take five to seven days before lab tests confirm a West Nile virus case. Doctors said they often begin treatment before getting those results.
Hasbun said the majority of undiagnosed cases are likely in younger, healthier adults whose immune systems can fight the virus.
About 2.5 percent of Texans are immune from West Nile virus, because, studies show, they have had the virus at some point in their life.
"We presume it's life-long," said Hasbun. "We've seen antibody fighters persist for years, but there are no good studies to tell us for sure it's going to be life-long."
CDC officials said they expect the number of West Nile virus cases in Texas and across the country to increase through the end of September.
Doctors recommend getting checked out if you have a headache, bad fever, body aches and rashes.