Residential flooding following torrential downpours, hurricanes and other severe weather events is one of the most heartbreaking headaches faced by a homeowner.

Drying out and cleaning up after a flood can be a laborious, expensive and exhausting experience with much attention paid to salvaging what hasn’t been claimed by floodwaters. However, there are a few side effects of flooding — some standard, some a bit unexpected depending on where you live — that can adversely impact the health, well-being and sanity of flood victims.

The above photo shows debris-filled floodwater in Texas after Hurricane Harvey tore through; you can see car parts, broken wood planks and various containers in the water. But for the sake of being prepared for just about everything — amphibians, reptiles and raw sewage included — here’s a look at more of the unsavory side effects of household flooding.

Sewage where it shouldn't be

Sewage water overflowing from sewage system Sewage water overflows from a sewage system (Photo: A_Lesik/Shutterstock)

Heavy, steady rains can spell relief in drought-prone areas but with torrential downpours comes a rather gruesome side effect: backed-up sanitary or combined sewage lines. Excessive amounts of stormwater brought on by localized flooding can enter overworked and antiquated sewer systems and cause overflow to run into the street, possible into your home. Overworked sewer systems can result in overflowing toilets, raw sewage-leaking bathtub drains and more.

Unbeknownst to many homeowners, sewer-related backups are not covered by most homeowner’s insurance policies or flooding insurance; in most instances, protection against blocked private (lateral) and main sewage lines must be purchased separately as an additional rider at a nominal cost.

Clean-up following a sewage backup requires that homeowners practice extreme caution given the risk of coming in direct contact with dangerous pathogens. The Massachusetts department of Energy and Environmental Affairs offers a comprehensive guide on how to proceed.

Bacteria, and not the good kind

E. coli bacteria E. coli bacteria, which can be found in floodwater, can cause illness outbreaks after natural disasters. (Photo: dreamerb/Shutterstock

Outbreaks of vomiting and diarrhea tend to happen during natural disasters, including flooding, the Centers for Disease Control and Prevention (CDC) says. Bacteria, parasites and viruses, such as the norovirus, can spread as homes lose electricity, people gather together in close spaces and access to clean water becomes limited.

Floodwater in two Houston neighborhoods after Hurricane Harvey contained E. coli at a level more than four times that considered safe after breaches at 40 waste treatment plants, according to the New York Times. "Scientists found what they considered astonishingly high levels of E. coli in standing water in one family’s living room — levels 135 times those considered safe — as well as elevated levels of lead, arsenic and other heavy metals in sediment from the floodwaters in the kitchen.public housing development," the Times reports.

In addition to E. coli and heavy metals, the Occupational Safety and Health Administration (OSHA) says floodwater also may contain infectious organisms, including intestinal bacteria such as salmonella, and shigella; Hepatitis A; and agents of typhoid, paratyphoid and tetanus.

OSHA says symptoms generally include nausea, vomiting, diarrhea, abdominal cramps, muscle aches and fever. The most common source of illness during a flood is through consuming contaminated food or water. The exception is tetanus, which is when an infectious disease enters the body through a cut in your skin, affecting the nervous system and causing spasms.

The CDC says to seek medical attention or treat open woulds right away. Washing hands regularly, designating a toilet seat for people with diarrhea, using hand sanitizer and separating people who are ill from those who are healthy can help reduce illnesses. And follow any boil-water advisories that may be in effect.

Mosquitoes and standing water

mosquito biting Mosquitoes lay eggs in standing water, and as adults (Photo: John Tann/flickr)

Near or directly in bodies of stagnant water of pretty much any shape, size or form — marshes, puddles, lakes, irrigated pastures, streams, clogged gutters, flower pots, half-empty birdbaths and the list goes on — is where annoying and potentially deadly mosquitoes choose to lay their eggs. And generally, these disease-carrying vectors in their adult form don’t stray too far from where they were born.

Residential flooding can spell trouble when it comes to plagues of mosquitoes, which could carry Zika, West Nile or other harmful viruses. Which is why after Hurricane Harvey hit parts of Texas, state health officials enlisted U.S. Air Force planes to do nighttime aerial spraying of insecticides over three counties, with more to come, Reuters reports.

Most mosquitoes that appear after floods are not the disease-carrying kind but can hinder recovery operations by swarming residents and cleanup workers, Texas Department of State Health Services spokesman Chris Van Deusen told Reuters.

The most effective way for homeowners to control mosquito populations following heavy rain and flooding is through source reduction or the elimination of the places where these particularly pesky insects breed and thrive — old tires, buckets, plastic wading pools, wheelbarrows, etc.

Mold and all that comes with it

Mold growing on the walls in a water-damaged home Mold growing on the walls in a water-damaged home (Photo: D_Townsend/Shutterstock)

Mold growth and the myriad health concerns that come along with prolonged exposure to spores are a massive concern following residential flooding that can occur in the wake of severe weather events such as hurricanes. Discolored walls and ceilings, signs of water damage and a foul, musty odor are all dead giveaways that action should be taken immediately.

If in doubt, a mold remediation specialist can help identify the presence of health-compromising microscopic fungi. However, your eyes and nose are generally the best ways to detect an infestation.

A basic, initial step is to remove all wet possessions and building materials from a home within 24 to 48 hours of flooding as recommended by the CDC. If it cannot be dried, cleaned and replaced, the item should be discarded — this particularly applies to carpeting, ceiling tiles and drywall. It is crucial to also air out a home by opening doors and windows and employing fans, air conditioners and/or de-humidifiers. Cleaning semi-porous and nonporous items with soap and water or a commercial mold remediation product can further prevent mold growth as can basic moisture control practices such as increasing air circulation, fixing leaks, cleaning air ducts and eliminating sources of indoor condensation.

Fuel where it shouldn't be

Pouring gasoline into a boat engine Motor boats operating through floodwaters contribute to gasoline seeping into the water. (Photo: Sergey Ryzhov/Shutterstock)

Alexandra Spychalsky, who lived in the path of Hurricane Sandy in 2012, writes for Bustle about the hazards of gasoline leaking into floodwaters:

More than a week after Hurricane Sandy struck my town, the block I lived on reeked of gasoline. My neighbors had filled their propane tanks days before the hurricane, which then knocked over and poured into the rushing floodwaters during the storm surge. The prevalence of boats in the area also contributed to the seepage of gasoline into floodwaters, which then dispersed throughout the neighborhood. Everything in my home that had touched floodwater had the distinct smell of gasoline on it.

Snakes, crocodiles and frogs

Cottonmouth snake In the South, cottonmouth snakes have been known to enter homes with rising floodwaters. (Photo: jo Crebbin/Shutterstock)

Many flood-stricken homeowners, preoccupied with salvaging possessions and filing insurance claims, often neglect to remember that with rising waters sometimes come unwanted — and rather nightmarish houseguests — in the form of venomous reptiles.

Following the historic flooding that impacted large swaths of Australia in 2011, thousands of deadly displaced snakes (and crocodiles) terrified stunned residents of Queensland struggling to dry out. And this is a phenomenon not limited to Down Under.

During a 2015 flood in South Carolina, cottonmouth snakes were found in homes as floodwaters receded. The poisonous snakes washed ashore in Alabama that same year after a Christmas Day flood. But though they're dangerous, experts say if you don't touch them and leave them alone, they'll do the same to you.

Grif Griffin of Augusta Crime Stoppers painted a terrifying picture following the recent flooding of the Savannah River: "They're thousands of snakes that lived on this river and are now in people's sewers. Those snakes will come up through your drain.”

In a rather extreme example, Paul Marinaccio Sr. was awarded $1.6 million in compensation in 2013 after flooding from a development near his Clarence, N.Y. home turned his 40-acre property into frog-heavy wetlands. Unnerving for sure, but Marinaccio was really affected by the flooding as he suffers from a severe phobia of frogs stemming from a traumatic childhood incident.

“You people don't understand. I am petrified," explained Marinaccio in his 2009 testimony. “In the winter, it's OK, because I know there's no frogs. But in the summertime, I'm a damn prisoner in my own home.”

Editor's note: This story has been updated since it was originally published in September 2013.

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.