A U.S. Marine climbs out of an icy lake during the winter Mountain Leader Course at the Mountain Warfare Training Center.

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Cold has a drastic effect on humans. We weren't born with fur like our mammal cousins, so being caught in severe cold can lead to illness and even death. In fact, the total number of deaths goes up 15 percent in the winter thanks to hypothermia, pneumonia and influenza [source: globalbiowether.com].

Hypothermia is pretty simple -- your body loses more heat than it produces and your body temperature drops. If you're caught in the cold, watch out for the following symptoms of hypothermia:

  • slurred speech
  • stiff joints
  • loss of coordination
  • slow pulse
  • uncontrollable shivering
  • loss of bladder control
  • puffy face
  • mental confusion

To fight off hypothermia, find shelter from the wind and cover up with anything you can find -- blankets, sleeping bag, pillows or even newspaper. Most of your body heat is lost through your head, so cover your noggin. If you have on wet clothes, replace them with dry duds immediately. If you don't have anything dry to wear, it's better to strip naked and dry your clothes by a fire than to wear something wet.

If you're with someone who's slipping into hypothermia, handle him or her with care -- he or she could go into cardiac arrest. Keep him or her horizontal. Get into a sleeping bag with your partner or simply hug each other tight to create warmth. If you're not trapped in the wilderness, seek professional medical attention as soon as possible.