"There are a lot of imported cases of dengue every year into the United States," said Vance Vorndam, a microbiologist with the U.S. Centers for Disease Control and Prevention. "Texas is leading the pack this year because it's so close to Mexico."
New figures from the Texas Department of Health show that 18 cases were travel-related, most acquired in Mexico. One came from Brazil. Five cases were acquired in Texas, however. It has not been determined where the remaining two cases came from.
This is the state's biggest outbreak since 1995, when 29 Texans caught disease, seven of them acquired in-state.
Texas is the only state that has reported locally acquired cases in the past 50 years, Vorndam said. Although diseases like dengue, yellow fever and malaria were common in the U.S. earlier this century, they have been mostly wiped out.
In fact, modern conveniences like window screens and air conditioning are probably the reason dengue rarely spreads in the United States, Vorndam said. Dengue is spread only by mosquitoes, not person-to-person.
Dengue fever is a viral illness spread by the Aedes aegypti mosquito. Symptoms include high fever, severe headaches, joint and muscle pain, nausea, vomiting and skin rash. The disease usually lasts about two weeks and is rarely fatal. There is no vaccine or cure for dengue.
About 200 dengue cases were reported in the United States last year with 90 cases confirmed by CDC tests. All were acquired in other countries. Since dengue is rarely fatal, many cases might go unreported or misdiagnosed, however.
Texas is experiencing spillover from an outbreak in northern Mexico, where 7,000 cases have been reported this year.
Arizona had three suspected travel-related cases of dengue fever this year, and California had a handful of cases, according to the states' respective departments of health. New Mexico had none.
The Texas Department of Health has stepped up efforts to warn people about dengue, alerted doctors to the symptoms and gone through records to track down possible cases from earlier this year.
The most recent cases the state is reviewing are from August and September, department epidemiologist Julie Rawlings said.
Webb County, which includes the busy international port of Laredo, leads the state with 18 cases.
"We're having cooler weather which means the mosquitoes are slower and more sluggish and less voracious in their biting appetite, but they're still pretty much alive and they're still pretty much in quantity," said Jerry Robinson, Laredo-Webb County health director.
Health officials recommend people wear insect repellant, long sleeves and long pants to avoid mosquito bites. They also suggest emptying outdoor water containers like pet dishes.
Many border counties also have activ fogging campaigns to kill mosquitoes.