Drinking or eating anything that has come in contact with floodwaters can lead to cryptosporidiosis, E. coli or giardiasis. While cryptosporidiosis and giardiasis are brought on by parasites, E. coli is caused by bacteria.
Symptoms from each include diarrhea, gas, nausea and vomiting. Cryptosporidiosis, however, can even be fatal for those with weakened immune systems, such as AIDS or cancer.
Open wounds and rashes that are exposed to floodwater can cause tetanus or Vibrio vulnificus. Tetanus is a bacterial infection, and it can enter the body through breaks in the skin like a cut.
You should also be aware of chemical hazards from materials that may have spilled into the water. And be cautious of electrical hazards, since there are puddles that may be electrified due to fallen power lines.
Curious about other diseases you can catch? Take a look at the full list at CDC's official website.