The Early Show medical contributor Dr. Mallika Marshall
"The flooding and water surges can cause the public water supply to become contaminated," she says, "and put people at risk for all types of illnesses, such as hepatitis and dysentery and other intestinal infections. So, until local authorities have actually deemed the public water supply safe, you really need to boil your water or use distilled or bottled water in the meantime. And certainly don't eat any food that's been contaminated with the water, unless you've properly cooked it.
If your power has been out for some time, she recommends throwing the perishable food away and eating only canned foods and nonperishable items.
The floodwater itself poses great danger, Marshall says, because it contaminated with sewage, agricultural waste and industrial waste.
"It has chemicals in it," she says. "So you certainly don't want to wade in the water. You don't want to allow your children to play in the water. You certainly don't want to drive through floodwaters, because your car could be swept away or stall, and then you're in big trouble.
"This type of water can also attract mosquitoes, which also can carry disease. So you want to wear protective clothing, long sleeved shirts, long pants, so you don't get mosquito bites."
A risk many people don't think of comes from using stoves, generators and other alternative supplies of power, which can produce carbon monoxide —an odorless and colorless gas.
"You may be exposed without even knowing it," Marshall says. "Don't use these items unless you are in a well-ventilated area."
Marshall also cautions that going home can be dangerous.
"People are anxious to get back to their homes, or what may be left of their homes, but you really need to talk to the local authorities to find out if it's safe to return," she says, "because a lot of these buildings are unstable. You want to look for downed electrical lines, glass, and metal and nails that you can injure yourself on. Talk to someone before you get back to your home. If it looks unstable, get out."