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What Pathogens Are Found in Sewage and Flood Water?

Last updated October 25, 2026

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The short answer

Bacteria in Sewage and Flood Water

Flood water often mixes with sewage, animal waste, and runoff, bringing in bacteria that can make you sick. E. Coli and Salmonella are common, and both can cause diarrhea, cramps, and fever. Another concern is Leptospira, which can enter through cuts and lead to a more serious infection.

Staphylococcus and Streptococcus bacteria can also be present, especially if the water touches open wounds. These can cause skin infections that spread quickly. If you have any cuts or sores, keep them covered and wash with clean water and soap after any contact with floodwater.

  • E. Coli: causes stomach cramps and diarrhea
  • Salmonella: leads to food poisoning symptoms
  • Leptospira: enters through skin breaks and can be severe
  • Staphylococcus: causes skin and soft tissue infections
  • Streptococcus: can cause strep throat or skin infections

Viruses Carried by Flood Water

Viruses are another threat in sewage-contaminated water. Hepatitis A attacks the liver and spreads through ingestion of contaminated water or food. Norovirus is highly contagious and causes vomiting and diarrhea, often leading to dehydration if you are not careful.

Rotavirus is especially dangerous for young children, causing severe diarrhea. While these viruses do not survive long outside a host, flood water can still carry them from overflowing sewage systems. Always wash your hands thoroughly with soap and clean water after being near flood water.

  • Hepatitis A: liver infection from contaminated water
  • Norovirus: causes stomach flu symptoms
  • Rotavirus: common in children, leads to diarrhea
  • Enteroviruses: can cause respiratory and intestinal illness

Parasites and Protozoa

Parasites like Giardia and Cryptosporidium are common in flood water contaminated with animal or human waste. These microscopic organisms cause intestinal illness, with symptoms like diarrhea, stomach pain, and nausea. They are resistant to chlorine, so standard water treatment may not kill them.

Another parasite, Toxoplasma, can be present in cat feces that wash into floodwater. It poses a risk to pregnant women and people with weakened immune systems. If you feel unwell after exposure, see a doctor and mention that you came into contact with flood water.

Fungi and Mold Spores

Flood water leaves behind moisture that encourages mold and fungi to grow on walls, floors, and furniture. Mold spores can become airborne and cause allergic reactions, asthma attacks, and respiratory infections. People with mold allergies or breathing conditions should avoid the affected area until it is dried and cleaned.

Some molds, like Stachybotrys chartarum, are sometimes called toxic mold, though any mold can be harmful in large amounts. Drying out the home within a day or two helps reduce mold growth, but porous materials like drywall and carpet may need removal. Mold professionals can test and remediate if the growth is extensive.

How to Protect Yourself

The right protection is to avoid contact with flood water altogether. Wear rubber boots, gloves, and a mask if you must enter a flooded area. Wash any exposed skin with soap and clean water as soon as possible, and do not eat or drink anything that touched the water.

After the water recedes, remove standing water and dry out the space quickly. Items that cannot be cleaned, like mattresses or stuffed toys, should be thrown away. For thorough cleanup and sanitation, local water damage pros can handle the job safely, especially for sewage backups.

If you live in Sammamish, keep the number of a water damage cleanup service handy before a flood happens. Acting quickly reduces health risks, but never rush into a flooded basement without proper gear. Your health comes first.

  • Wear waterproof gloves, boots, and a mask
  • Wash hands with soap and clean water after contact
  • Do not eat or drink anything exposed to flood water
  • Remove standing water and dry items within 24 to 48 hours
  • Discard porous items that cannot be disinfected
  • See a doctor if you develop symptoms after exposure

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Frequently asked questions

Can I get sick just from breathing the air near flood water?

Yes, flood water can release mold spores and bacteria into the air, especially when it is disturbed. Breathing these in can cause respiratory irritation or infections, particularly for people with asthma or allergies. Wearing an N95 mask helps reduce the risk.

How long do pathogens survive in flood water?

Many bacteria and viruses survive only a few days in water, but parasites like Giardia can last for weeks. Mold starts growing within 24 to 48 hours on wet surfaces. The longer water sits, the higher the risk, so remove standing water as soon as it is safe.

Is it safe to clean up flood water myself?

Small areas with minimal contamination might be manageable, but sewage backups and large floods are risky. Without proper protective gear and disinfectants, you could expose yourself to serious pathogens. The pros have the equipment and training to handle contaminated water safely, so consider hiring them for major cleanup.

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