Tarrant, Dallas officials take different approaches to Chikungunya

09/03/2014 12:00 AM

09/02/2014 4:38 PM

Now that Chikungunya cases have been confirmed in North Texas, officials in Dallas and Tarrant counties are taking different approaches to combating the mosquito-borne virus.

Since late December, Chikungunya has spread across the Americas, with most of the half-million suspected cases reported in the Caribbean. Two cases have been confirmed in Dallas County, two in Tarrant County and one in Collin County. All five patients were infected with the virus while traveling in the Caribbean.

Statewide, 15 imported Chikungunya cases have been reported.

While no known cases have originated in North Texas, Chikungunya can be carried by Aedes mosquitoes, which bite during the day and are present in North Texas. The West Nile virus is carried by Culex mosquitoes, which are more active at night.

In Dallas, officials are ordering traps and operating under the assumption that the virus will eventually get there.

“The projection is next year or the following year,” said Zachary Thompson, director of Dallas County Health and Human Services. “We got traps in. If you go by West Nile, it first showed up in New York in 1999 and we saw it in Dallas County in 2002. We just don’t know how swiftly Chikungunya will move.”

The traps are different from the ones used to test for West Nile, officials said.

Tarrant County is taking more of a wait-and-see approach.

“We believe that it will follow the same course that we have seen by the dengue virus, where we see a lot of imported cases and sporadic local outbreaks,” said Anita Kurian, Tarrant County Public Health’s associate director for environmental health and disease control. “We haven’t had a dengue virus case in a long time.”

Texas had 154 cases of dengue fever from 2003 to 2012, according to the Texas Department of State Health Services. Eight were reported in Tarrant County.

Different from West Nile

In Swahili, Chikungunya means “that which bends up,” referring to the joint pain it can cause, which is similar to the dengue virus.

Chikungunya has no known vaccine, and up to 90 percent of those who get it experience some symptoms, usually high fever, headaches and severe joint pain. Chikungunya complications tend to occur more often with infants, those over 65 and people with diabetes or hypertension. Chikungunya has no known cure but is rarely fatal.

West Nile is already established in the local bird population, but mosquitoes can carry Chikungunya only after biting an infected human.

Both Tarrant County residents — one from Mansfield and one from Fort Worth — are past the time of being infectious, officials said.

“The surveillance and the response measures for this particular mosquito-borne illness is different from the other mosquito-borne illness that is prevalent in our community,” Kurian told Tarrant County commissioners last week. “In the absence of local transmission, it is not recommended — neither is it warranted — to trap, test or spray.”

One local researcher, who oversees the University of North Texas Health Science Center’s West Nile trapping and testing program, expressed skepticism that Chikungunya will become established in North Texas.

Joon Lee, an assistant professor of environmental and occupational health sciences, said conditions are not the same locally as in parts of the Caribbean.

“Based on available information on the CHIKV epidemics and ecology, there will be a limited chance for the virus to establish in North Texas, where conditions unlikely support local maintenance of the virus,” Lee said.

“However, there is always a chance for an outbreak of CHIKV from an imported case and … the possibility for an outbreak would increase during the mosquito season if imported case numbers continued to increase in the region.”

If a local outbreak occurred, Lee said, a limited trapping and testing program might be necessary around the neighborhood where cases were reported.

Like Kurian, Lee doesn’t expect large-scale Chikungunya outbreaks across the U.S.

For one thing, the number of Aedes mosquitoes “is not comparable with that of the Caribbean countries,” Lee said. “More importantly, we do have a better public health system that could quickly detect the human cases and manage the virus transmission at a minimum level.”

Travel precautions

Kurian said local physicians must be kept aware of the virus and encouraged to test those who have symptoms and recently traveled to the Caribbean. Doctors should report suspected cases immediately rather than waiting 10 to 14 days for test results.

The only place where local transmission has been reported is in Florida, with six cases. There have been 201 locally transmitted cases in Puerto Rico and 21 in the U.S. Virgin Islands, according to the Centers for Disease Control and Prevention.

In its Aug. 22 report, the Pan American Health Organization reported 583,504 suspected cases across the Americas, with the overwhelming majority in the Caribbean. The most cases by far — 370,141 — were in the Dominican Republic. The U.S. mainland has seen 645 imported cases.

The CDC has advised travelers to take precautions while traveling in the Caribbean because local transmission has been reported in 25 countries in the region.

Since the Aedes mosquito bites during the day, local health officials are encouraging residents to fundamentally change their habits by applying insect repellent or wearing long sleeves whenever they go outdoors.

That may seem like an uphill battle, but Dallas County’s Thompson said attitudes changed after the 2012 West Nile outbreak.

“I think it was a hard sell up until 2012,” Thompson said. “But as you see more cases confirmed in Dallas or Tarrant County — or around North Texas — those attitudes start to change.”

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