Dr. Terry Gentry, an associate professor at Texas A&M University, examined small samples of both drinking water and floodwater from Cypress, Texas--a community just outside of Houston--at the university's microbiology lab. While the results of the lab tests revealed that the drinking water was safe, Gentry found that the levels of E. coli and coliform bacteria in the floodwater samples raised cause for concern.
"We saw elevated levels of E. coli," Gentry told ABC News. "This indicates the very likely presence of pathogenic bacteria viruses and other organisms that could cause disease in some individuals."
The Harris County Department of Health told ABC News in a statement that "the results in the report would be exactly as we would expect," adding that with the flooding, "the waters in the streets can easily be overrun and contaminated with sewage, trash, and displaced animals, making it dangerous and unsafe."
Dr. Susan Whittier, an associate professor at Columbia University in New York City, told ABC News that rescuers and residents exposed to the floodwaters should be cautious, especially if they had open wounds.
Whittier also advised people to try and stay "clean as much as possible."