It can also carry animal waste from fields and forests."
MORE: Life-Threatening Flooding.’
What to Know About Hurricane Harvey Health and environmental experts recommend people avoid intentional contact with flood water due to potentially high levels of contamination.
The United States Environmental Protection Agency (EPA) says substances like raw sewage and other chemicals can get into the water, as storage containers of industrial chemicals or solvents can be disturbed or moved by surging flood waters.
“ Anyone experiencing these and any other problems should immediately seek medical attention,” says the EPA.
"The bacterial count in floodwater is extremely high," says Bradley.
Mosquitoes and the diseases they carry, such as Zika and West Nile Virus, are also a health hazard, even after the rains subside.
Mosquitoes thrive in standing water, and after Hurricane Katrina, the number of cases of West Nile Virus doubled in affected areas in Louisiana and Mississippi.
The moisture from standing water after a flood can also spur mold growth, which is why proper clean up is critical for homes and buildings.
With so many residents forced to walk through high flood water, Bradley recommends that anyone exposed get out of wet clothes quickly, rinse their bodies entirely, and seek medical attention immediately for any infections or unusual symptoms such as upset stomach or diarrhea.