One Health Resource Center

One Health Resource Center

August 30, 2017
5 min read

Harvey flood victims could face ‘unusual’ infectious disease threats

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Photo of Bernard Camins
Bernard Camins

Storm victims in Texas are at an increased risk for infection in the wake of catastrophic flooding caused by Harvey, which may bring them into contact with pathogens capable of causing disease, including some that may be unusual to physicians.

Among potential threats, diarrheal illnesses and skin infections are the likeliest to spread as storm victims come in contact with contaminated floodwaters, according to Bernard Camins, MD, associate professor of medicine at the University of Alabama at Birmingham.

“These are everyday things that happen, but in times of flood, the risk is magnified,” Camins said in an interview. “Not everyone will get them, but people with weakened immune systems, the elderly and people on immunosuppressants are more prone to developing these diseases.”

Record flooding

According to news reports, at least 30 people have died since Harvey made landfall in Texas on Friday night as a Category 4 hurricane with maximum sustained winds of 130 mph. Harvey was downgraded to a tropical storm but loitered near the Texas coast, dumping close to 50 inches of precipitation on some areas. It made landfall again on Wednesday morning in Louisiana.

The storm has caused record flooding in many places, including Houston, the nation’s fourth largest city. The water itself can be deadly, trapping people in their houses or cars. Floodwaters that carry sewage and other contaminants can be dangerous on a microscopic level, as drinking or eating anything contaminated with it can cause diarrheal illnesses, according to the CDC.

These illnesses may include commonly seen infections caused by norovirus, Escherichia coli, Salmonella and Shigella, but the magnitude of the flooding and sheer number of victims means there also could be an increase in infections that physicians do not see as often, including some caused by infected wounds, Camins said.

“What clinicians should look out for are skin and soft tissue infections caused by nonconventional bacteria. You still have to worry about Staph infections, but certainly you have to worry about unusual pathogens as opposed to the usual pathogens,” he said.

According to Camins, these include Vibrio vulnificus, which lives in warm, coastal waters. Vibrio illnesses such as V. vulnificus kill around 100 people in the U.S. each year and are usually caused by eating raw or undercooked shellfish, most often oysters, according to the CDC. However, after Hurricane Katrina struck the Gulf Coast in 2005, devastating New Orleans, the CDC identified 22 new cases of Vibrio illness associated with the storm, including five deaths.


Eighteen of the cases — including all five deaths — were caused by wounds that became infected through contact with floodwaters contaminated by V. vulnificus, V. parahaemolyticus and nontoxigenic V. cholerae. Three of the deaths were associated with V. vulnificus infection, and the other two with V. parahaemolyticus, according to the CDC.

Camins said Staphylococcus aureus infections also have been described in the wake of hurricanes, but probably stem from hygiene issues related to overcrowding in shelters rather than contact with floodwaters.

“They probably already have Staph in their body and haven’t been able to shower or care for themselves, and so they end up with Staph infections,” he said. “From a physician’s standpoint, being exposed to floodwater, you have to think about the non-Staph bacteria that can potentially cause an infection.”

Prevention is key

Camins recommends that flood victims inspect their extremities as soon as they can, making sure they do not have any cuts or scrapes. He said tetanus, which is caused by spores of bacteria found in soil, dust and manure that enter the body through broken skin, is more of a concern in dry conditions but recommended that storm victims in Texas make sure they are vaccinated against it.

He said storm victims can mitigate their risk for infection by washing their hands, especially in overcrowded areas, and by not drinking unsafe tap water. The Texas Department of State Health Services (DSHS) warned residents in affected areas to listen for announcements about the safety of public drinking water and to follow alerts to boil water when they are issued.

According to the DSHS, water for drinking, cooking and washing should be brought to a rolling boil for at least 1 minute and then cooled. The department said water can also be disinfected with a small amount of regular, unscented household bleach — one-eighth teaspoon, or about eight drops, per gallon. If the water is cloudy, one-quarter teaspoon should be used, according to the CDC.

“If they have access to bottled water, that may be better. It may be easier than finding a pot and fire to boil the water,” Camins said.

The DSHS said residents should not eat food that has been in contact with floodwater, been at room temperature for more than 2 hours or has an unusual odor or color. It said babies on formula should be given ready-to-feed formula or powdered formula that is prepared with bottled water.


“A lot of it is prevention,” Camins said. “It’s not that [infections are not] going to happen, but if everybody mitigates the risk, then it won’t happen as much.”

Mold and mosquitoes

After the storm, people will be exposed to different risks when they return to houses damaged by floodwaters.

To protect against mold, the CDC recommends cleaning homes quickly, opening doors and windows and using fans to dry wet areas. Wet items and surfaces should be cleaned with detergent and water, and mold should be cleaned with no more than one cup of household bleach mixed with one gallon of water used in a ventilated space, according to the CDC.

According to Camins, although it is important to clean well and to get rid of anything that cannot be cleaned, mold is more of a threat for some people than for others.

“Lay people are very scared of mold,” he said. “Sure, you can’t say you’ll never die from a mold infection, but it is more worrisome if you’re immunocompromised. If you have a healthy immune system, a lot of times it’s related to allergic reactions.”

According to the CDC, rain and flooding from a hurricane may also lead to an increase in numbers of mosquitoes, making mosquito-borne diseases like West Nile virus — or perhaps Zika virus — a concern for people in affected areas.

In the wake of Hurricane Katrina in 2005, reported cases of West Nile virus “sharply increased” in affected areas of Louisiana and Mississippi, according to researchers. Camins said the virus could be a problem after Harvey in people who have not been previously infected or those who have risk factors like old age, hypertension and diabetes.

“When Katrina happened, West Nile was still pretty new, so people hadn’t necessarily been exposed then,” Camins said. “But West Nile is now endemic [in the U.S.], and 80% of people who get infected are asymptomatic, so we don’t know who’s already infected and will not be infected again, and who hasn’t been. It’s really hard to know.” – by Gerard Gallagher


Caillouet KA, et al. Emerg Infect Dis. 2008;doi:10.3201/eid1405.071066.

CDC. MMWR Morb Mortal Wkly Rep. 2005;54:928-931.

For more information:

CDC. After a hurricane. 2017.

CDC. Guidelines for the management of acute diarrhea after a disaster.

CDC. Hurricane PSAs. 2017.

CDC. Infectious disease after a disaster.

CDC. Protect yourself from animal- and insect-related hazards after a disaster. 2014.

Texas Department of State Health Services. DSHS provides flood precautions as Hurricane Harvey affects Texas. 2017.

Disclosure: Camins reports no relevant financial disclosures.