Hurricane Harvey could ignite a surge in mosquitos capable of spreading Zika in southeast Texas, public health experts warned even as the storm was lashing the Gulf Coast over the weekend.
In the short term the storm will actually be a boon, flooding out mosquitos. But the standing water Harvey will leave behind will become their perfect breeding ground, including for Aedes aegypti mosquitos blamed for spreading the disease.
Officials are urging those returning to their homes after the storm to dump flower pots, bird baths and other containers with standing water.
“It’s been a significant part of our messaging for Zika all along and definitely will be something we’re talking about following Harvey,” said Chris Van Deusen, spokesman for the Texas Department of State Health Services.
The U.S. has enjoyed a relatively Zika-free year in 2017, with just a single case of the disease being spread locally by mosquito. That case came in Hidalgo County, along the border with Mexico.
Tamaulipas, the Mexican state on the other side of the boundary from Hidalgo Country, is one of three hard-hit states in Mexico where the number of Zika cases has risen this year.
On Thursday, Texas added three counties to its list of places where it’s advising women to obtain routine testing for Zika if they are pregnant. The new additions bring the total number to nine.
Hurricane Harvey tracked north as it made landfall over the weekend, above the counties at most risk of Zika transmission along the Rio Grande, yet it could throw a climatic curveball into the threat in a large swath of the state.
Though the hurricane should knock out some insect vectors, “with sufficient rain and the resulting standing water, the mosquito numbers may rebound as quickly as 5 to 7 days after the rainfall, and possibly be even higher than they were,” said Christopher Vitek, an associate professor and mosquito expert at the University of Texas, Rio Grande Valley.
Some of the rebounding mosquitos will be “floodwater mosquitoes,” which transmit West Nile virus, though “breeding mosquitoes” that can spread Zika will find new places to multiply.
“Following a hurricane there may be an increase in debris around people’s houses, as well as water in those containers,” Mr. Vitek said. “If that happens, and those breeding sites are left unattended, then the population of mosquitoes capable of transmitting Zika may increase.”
Texas recorded six cases of mosquito-borne Zika last year.
Florida, the only other state with local transmission, saw more than 200.
Florida has yet to see any confirmed local cases this year, leaving Texas the chief worry spot.
“Given that transmission of Zika and other arboviruses in South Texas can continue well into the fall, on balance I believe the hurricane could make things worse,” said Peter J. Hotez, dean of the National School of Tropical Medicine at the Baylor College of Medicine in Houston.
Dr. Hotez said the effect of hurricanes on insect-borne diseases requires more study, though he pointed to a scientific paper that found West Nile cases more than doubled in 2006 among regions of Louisiana and Mississippi that were battered by Hurricane Katrina in late 2005.
“There may be some short term benefits in term of washing away mosquito breeding sites during the storm,” he said, “but there is some evidence that over time hurricanes could have a detrimental effect in terms of promoting West Nile Virus infections — transmitted by Culex mosquitos — in the region, but also viruses such as Zika and dengue transmitted by Aedes mosquitos.”
• Tom Howell Jr. can be reached at email@example.com.
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