As it moves away from Southeast Texas, Hurricane Harvey leaves a number of public health risks along its path of flood and destruction.

Even as floodwaters have started receding in some places, experts warn that residents in Harvey-affected areas could still be exposed to numerous health threats, ranging from water contamination to psychological distress.

Dealing with these threats is one of the biggest challenges communities face in the wake of a natural disaster, when it's harder to receive medical assistance and people might not have access to basic resources like cash, medication and clean drinking water.

"The disruption of the event itself and access to care tends to be the more problematic aspect," said Courtland Robinson, an associate professor at the Center for Humanitarian Health at the Johns Hopkins Bloomberg School of Public Health in Maryland, who has participated in recovery missions after Hurricane Katrina and other natural disasters.

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Here are some of the health risks experts are concerned with in extreme flooding events like Harvey – and some precautions impacted residents can take to prevent them.

Contaminated water

The torrential rain that Harvey dropped has left a large part of Southeast Texas underwater. Experts warn that floodwaters can be contaminated with chemicals from industrial plants and agro-businesses, as well as with human waste, as sewage systems fail.

Researchers at Texas A&M University tested floodwaters from Northwest Houston on Tuesday and found levels of E. coli that were 125 times higher than what is considered safe for swimming.

"If you see a lot of E. coli, that indicates that there's a lot of fecal material in the water, and we know that fecal material can carry a lot of different types of organisms," said Terry Gentry, an associate professor at Texas A&M University, who led the study. He adds that these organisms can cause minor health problems, like an upset stomach, and more serious diseases such as hepatitis or salmonella.

What you can do:

  • If officials in your area have issued "boil water alerts" or you have a private well that could be contaminated by floodwater, use only bottled, boiled or treated water.
  • Don't drink water from unknown sources.
  • Don't eat food that has touched floodwaters.
  • Don't drink and avoid touching floodwater.
  • If you do get in contact with floodwater and you have a skin cut or abrasion, Gentry recommends washing the area immediately with clean water, treating it with some type of antibiotic and monitoring the wound for signs of infection.

Click here and here for additional tips.

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Psychological distress

Robinson explains that anxiety is a big problem when a disaster hits, particularly if people lose access to basic provisions like food and water or lose contact with friends and family.

Psychological distress is also a concern in the long term.

"Over time, anxiety can also lead to depression — 'I lost my home, my job, I'm not sure where I'm going to rebuild. Can I go back to my neighborhood? Is that going to be declared unfit?'" said Robinson, adding that displaced people can also develop post-traumatic stress disorder.

What you can do:

  • Talk about what you experienced and express your feeling to others.
  • Try to keep routines in your family, like having meals together and participating in enjoyable activities. This will help restore a sense of order and normalcy.
  • Talk with children about their feelings and experiences and pay attention to changes in their behavior.
  • Talk to a professional about emotional distress by calling the Disaster Distress Helpline at 800-985-5990 or texting “TalkWithUs” to 66746.

Click here for additional emotional recovery tips, as well as how to help children and the elderly.

Mold

Mold can start growing in a home the day after a flood.

"As the water recedes, the mold issues became striking in a hot climate," warns Richard Jackson, a professor at the Fielding School of Public Health at the University of California, Los Angeles, who has also directed the National Center for Environmental Health at the national Center for Disease Control. Mold can affect the eyes and throat and increase the chance of asthma attacks and other respiratory problems.

What you can do:

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  • If your house was flooded, thoroughly dry it out.
  • Remove and throw away wet carpets.
  • Discard materials that easily absorb water (like wallpaper, mattresses and pillows) and clean floors, walls, countertops and other non-porous materials. Here's how.

Click here for more information on avoiding mold.

Mosquito-borne diseases

Large quantities of standing water make Harvey-affected areas prone to mosquitoes that could transmit Zika, dengue, West Nile virus and other diseases. "If it gets hot, the mosquito population will really bloom," said UCLA's Richard Jackson.

He said Texas has done a good job in terms of mosquito control but that Harvey has brought a new challenge.

"One of the key things is just to monitor it, not be surprised when it occurs and be prepared for what you have to do," Jackson adds.

According to the Austin American-Statesman, the Hays County Health Department alerted residents this week about these threats in a statement and recommended them to:

  • Drain all standing water that might have accumulated at their home or business.
  • Wear long-sleeve shirts and pants.
  • When outside, apply insect repellant that contains DEET
  • Put screens on their home's windows and doors
  • If the standing water can't be drained, apply mosquito larvicide

Other injuries

When rescue and recovery efforts are underway after a disaster, people can get injured by lifting heavy loads or removing debris, and they risk exposure to dangerous chemicals, such as carbon dioxide from generators, according to Robert Emery, the Vice President of Safety at the University of Texas Health Science Center at Houston.

He explained that extra care is necessary since emergency rooms are usually overflowing after a disaster. "I totally sympathize with people that want to get home and get their lives restored, but we have to have folks exercise caution and don't tackle things that you can't tackle. If you throw your back out trying to drag a wet mattress, getting health care for that will be difficult. So everybody has to operate within their boundaries, " he advises.

What to do:

  • Never use gas-powered generators inside your home.
  • Never mix bleach with products that contain ammonia. It could create toxic fumes.
  • Always wear shoes in areas that were flooded to avoid cuts from nails and other sharp objects.
  • If you have an injury that was exposed to floodwater, you could be at risk of contracting tetanus if you haven't had a tetanus vaccine in the last 10 years.
  • Stay hydrated.

For additional tips, click here, here and here.

Disclosure: Texas A&M has been a financial supporter of The Texas Tribune. A complete list of Tribune donors and sponsors is available here.

Read related Tribune coverage:

  • Hurricane Harvey ravaged the Texas Coast and left Houston grappling with unprecedented flooding. Do you need help? Or do you want to help those in need? Check out these resources. [Full story]

  • Immigration enforcement and Border Patrol officials reiterated last week that their agents are not conducting routine immigration operations during rescue efforts in Southeast Texas — despite rumors to the contrary. [Full story]

  • Texas school districts are preparing to take in students displaced by Harvey. [Full story]

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