Flood waters after a hurricane could be filled with a lot of unknowns.

"You don't know what the water has run over," says Dr. Brian Hiestand, Professor of Emergency Medicine at Wake Forest Baptist Medical Center.

He says it could contain any sort of chemical or industrial contaminants or it could also have animal waste if the water stream goes over a farm.

With those contaminants comes the risk of tetanus, a bacteria found in dust, soil and animal waste. It can get in to your system through open wounds and can typically lead to what's called lockjaw. Symptoms include stiffness in your jaw, neck or abdominal muscles; difficulty swallowing; fever; sweating; elevated blood pressure or rapid heart rate.

Dr. Hiestand recommends getting the tetanus shot every ten years, or every 5 if you've ever had a cut that's put you at risk for tetanus. He also recommends avoiding flood water if at all possible.

"So, in general, if you don't have to go in to flood water, it's probably not a good idea to start wading in areas you can't see."

But in the wake of a natural disaster, that's not always an option.

In the event of evacuation, Dr. Hiestand recommends keeping a list of medical conditions, medications and allergies to take with you if you need to seek medical help at a shelter. If possible, take your own medications with you, so you won't have to rely on getting prescriptions filled under evacuation circumstances.