Some of the biggest threats that appear during a flood are unseen. Deadly microorganisms like bacteria, viruses and parasites will thrive in floodwaters, waiting to invade someone’s body through an open cavity or wound. Here are several, harmful diseases caused by microorganisms that appear in floodwaters.


Amoebiasis is an amoeba-caused illness with the symptoms of vomiting and diarrhea. An infection may cause tissue damage to the liver or intestines. With treatment, death is uncommon, but the disease can be passed on to other people.


Cholera is caused by Vibrio cholerae that is spread through contaminated water. Diarrhea and severe dehydration are common symptoms. Although rare in many communities, cholera can spread when rivers, lakes or other large bodies of water flood into neighborhood streets.


Giardiasis is caused by the Giardia lamblia parasite. Common symptoms are diarrhea along with vomiting and abdominal pain. Not treating the disease may cause severe fatigue and weight loss for several months. Sufferers also lose nutrients and find it harder to concentrate and function normally.


Cryptosporidiosis develops when the Cryptosporidium parasite invades the intestines, causing prolonged periods of watery diarrhea. It results in a short-term infection that can be passed from host to host. Cryptosporidium can live outside of the body and resist being killed by disinfectants.

Typhoid Fever

Although not common in developed countries, typhoid fever can develop in people who are infected with Salmonella typhi, which spreads in sewer-infested floodwaters. The disease can be spread from one person to another without knowing it. The feverish symptoms appear several days or weeks after the infection.

During floods, disease-causing microorganisms are usually transmitted through the water. The type of waterborne disease that develops depends on where the flood damage in Mesa formed. In developing countries where sewer systems are less stable, more bacteria and diseases are present in the floodwaters. Anyone who lives in high-risk flood zones must know about the dangers of pathogenic microorganisms.