Short Answers to Hard Questions About Health Threats From Hurricane Harvey

September 1, 2017




Ruth Giraldo, a resident of Concord Bridge in northwest Houston, in front of her home on Wednesday. Credit Barbara Davidson for The New York Times

The devastation caused by Hurricane Harvey in Houston has brought a host of health questions from residents of the area and concerned relatives and friends. Here are some answers to common questions showing up in Google searches and on Facebook.

Can I get a bacterial infection from the dirty floodwaters?

Yes. Some Texas public health officials expect an increase in gastrointestinal problems from bacteria breeding in stagnant floodwaters that can contain Escherichia coli (E. coli), Shigella, and Vibrio vulnificus. The latter, which is present in the Gulf of Mexico, can cause terrible infections that can lead to amputations. It is harmful if swallowed or if it comes into contact with a cut.

In a report issued one month after Hurricane Katrina in 2005, the Centers for Disease Control and Prevention said it had counted 24 cases of hurricane-related wounds infected with Vibrio vulnificus or its relative, Vibrio parahaemolyticus, of which six were fatal.

If you have walked through floodwaters, it is best to throw out the clothes and shoes you wore, said Winifred J. Hamilton, director of the environmental health service at Baylor College of Medicine.

What about waterborne intestinal diseases like hepatitis or cholera?

Dr. David E. Persse, Houston’s chief medical officer, does not anticipate any big outbreaks. “We didn’t get a lot of people with those after other storms,” he said, adding that “if you look at other floods, you don’t see a lot of hepatitis. In poor countries, you see cholera, but we don’t have it here.”

Also, Houston – unlike New York and some other cities — has separate pipes for storm water and house sewage. “Our storm sewer system was overwhelmed, but our sanitary system did not get breached,” he said. “That water flows into treatment plants, and they did not get flooded or lose power that I know of.”

Is the drinking water supply really safe?

Houston health officials said there have been no breaches to the city’s main public water supply, and that the drinking water is fine. But, they have warned residents who rely on small municipal water systems of potential contamination and have urged them to boil their water.


Mugs filled with rainwater strewn about what’s left of a Port Aransas, Tex., gift shop on Wednesday. Credit Christopher Lee for The New York Times

What if we use a private water well, not a municipal system?

If you’re among the hundreds of thousands of Houston-area residents who rely on private wells, you are on your own. If flood water has gotten into your well, you need to get the water tested. Use bottled in the meantime.

“If you’re on a well, you are your water system,” said Professor Marc Edwards, a drinking water expert at Virginia Tech. “That is why we have a special outreach effort, a collaboration with Louisiana State University, trying to get information to people who have private wells.”

Can I get H.I.V. from exposure to the flood water?


How’s the air?

Not so good. In most cases the toxic air pollution given off by the refineries and chemical plants during emergency shut downs won’t cause severe problems right away. But older adults, those with asthma and the immune-compromised may develop inflammations and other ailments. Long-term risks won’t be known until health officials figure out what, exactly, has been spewed into the air.

Residents going back to their houses will have to rip out wallboard that has developed mold, which is also a health risk. And be careful when tearing out cabinets or walls: Houses may have asbestos and those built before 1978 are likely to have lead paint. You don’t want to expose yourself or your children.

What’s the risk of mosquito-borne diseases like Zika in the wake of the flooding?

At the moment, the risk is lower than normal. Floods and high winds whisked billions of mosquitoes and their larvae to their doom in the Gulf of Mexico. “When the water is raging and surging, everything’s washed away,” said Mustapha Debboun, chief of mosquito control for Harris County, which includes Houston.

But once the waters settle, there will be countless low spots, old tires, flowerpots and the like where mosquitoes can begin rebuilding their populations.

After Labor Day, Dr. Debboun said, he will send teams out to see how many land on an arm in a minute. If the situation gets bad enough, he said, he will start aerial spraying and probably ask for help from the federal agencies.

To spread Zika or dengue, mosquitoes would have to pick up the virus from the blood of humans who recently returned from areas with outbreaks. Throughout most of the Western Hemisphere, Zika cases are down by more than 90 percent from last year’s peaks, according to the Pan American Health Organization. However, Mexico is having a modest uptick this year, including cases in the state of Tamaulipas, which is just across the border from Texas’s southeast coast.

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A flooded farm field outside of Crosby, Tex., on Thursday. Credit Andrew Burton for The New York Times

What about other diseases spread by mosquitoes, like West Nile?

West Nile virus is endemic in the United States and outbreaks are triggered by several factors, including the concentrations of culex mosquitoes, humans who are not immune, and birds who are not immune. (The virus builds up to higher concentrations in bird blood than in human blood, so mosquitoes tend to pick it up from them to give to humans.) Birds were also probably driven away from coastal Texas by Hurricane Harvey’s winds.

In 2005, in the wake of Hurricane Katrina, there was initially no increase in cases of West Nile virus or St. Louis encephalitis, which is also spread by mosquitoes, noted Dr. Peter J. Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston. But a year later, there was a surge in dangerous “neuroinvasive” West Nile disease in the affected regions of Louisiana and Mississippi: Cases of encephalitis and meningitis more than doubled. Researchers from Tulane University’s School of Public Health and Tropical Medicine speculated that more people were bitten that year because they were outside doing reconstruction work or living inside partially-destroyed houses that mosquitoes could invade easily.

What about disease transmission in shelters?

“The big thing I’m worried about is norovirus,” said Dr. Persse, Houston’s chief medical officer. “That’s the ‘cruise ship virus’ – with a lot of people in a small space, it can spread really quickly.”

The disease causes vomiting, diarrhea and dehydration. It is not normally fatal to otherwise healthy people, but severe dehydration can kill frail older adults.

In shelters, it can be hard to control. Health officials try to stop outbreaks by quickly taking the sick to separate rooms where they are given food and entertainment, there is no wait for toilets and the floors are washed frequently with bleach.

Dr. Persse’s medical teams are walking through shelters now looking for people vomiting. Shelter populations are thinning out as people return home or find other places to stay, so the danger is decreasing.

After Hurricane Katrina, 200,000 refugees ended up in 750 shelters in 18 states, and there were scattered outbreaks of various diseases, the C.D.C. said.

About 1,000 cases of diarrhea in more than 20 shelter clusters were reported. One Dallas-area shelter had 30 skin infections with MRSA, an antibiotic-resistant form of staphylococcus bacteria.


Matthew Trent moved a flood-damaged refrigerator in front of his home in Port Aransas. Credit Christopher Lee for The New York Times

Officials worried about tuberculosis transmission, one new case was found in a shelter. Health authorities were able to trace about 70 percent of the patients they knew had previously been on TB treatment so they could be kept on it, the C.D.C. said. TB patients who are taking their antibiotics are usually not infectious.

Can I get sick from exposure to a corpse?

That is not likely, but dead bodies may leak feces that will contaminate the water and could lead to gastrointestinal infections.

What should I do when I get home?

First, make sure that your electrical system is safe and there are no gas leaks. Check for structural damage.

Once inside, there is likely to be toxic sludge. Throw out any food that has come into contact with floodwaters, unless it’s well packaged in metal, waterproof glass or hard plastic containers. Even then, wash it off first.

Don’t run gas-powered electrical generators indoors or use gas or charcoal grills indoors. These can cause carbon monoxide to build up and kill you.

“Many people are already back into their homes that have been flooded with two or three feet or more of water,” said Winifred J. Hamilton, director of the environmental health service at Baylor College of Medicine. “We are already seeing piles of carpet and sofas on the curb.

“As the water dries,” she said, “you are going to have mold spores made airborne.”

She advised anyone who has asthma, respiratory disease or is immune-compromised not to take on the cleanup. “You should get someone else to do it if possible,” she said. “And wear personal protection equipment so that you are not breathing in toxins.”

Any other advice?

Yes, watch out for snakes. Humans aren’t the only creatures who were seeking dry ground.

Denise Grady contributed reporting.


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