Spoiled snacks on the doorstep
Mail-order food gifts are great unless the weather outside is too delightful to keep them cold. Left out too long, even well-packaged perishables such as cheese and cheesecake become frightful. What to do: Open perishables immediately. If food temperature is above 40 degrees, call the company that sent it and don't eat any. Not even a nibble. Seriously, don't.
Maladies under the mistletoe
Before you pucker up, consider a cheery note from a British Columbia health department: "Colds, kissing disease [mononucleosis], herpes infection, warts, hepatitis B and meningococcal disease may all be transmitted by kissing." What to do: Smooch with discretion. (Thinking about warts should help.)
Tummy troubles in tight places
Getting away for the holidays? Norovirus, a.k.a. "winter vomiting disease," causes more than 20 million cases of gastroenteritis every year. It spreads easily in tight quarters such as hotels, restaurants, airplanes and cruise ships and is often transmitted on uncooked greens, fruit and shellfish. What to do: Wash hands often and don't share utensils. If someone becomes ill with nausea or diarrhea, disinfect contaminated surfaces with a bleach solution.
(Hum)bug on the tree
Critters on conifers are harmless and usually remain unnoticed until you haul the tree to the curb, but a few mites, spiders or praying mantids might hop off or hatch and stay awhile. What to do: Before taking a tree inside, shake it to get rid of loose bugs and remove obvious eggs and nests. Don't spray with insecticide - it's flammable.
Flu in the air
Influenza viruses thrive in late fall and early winter and spread from person to person through the air, particularly cold, dry air. Family gatherings, holiday crowds and even Santa's lap provide plenty of transmission opportunities. What to do: Steer clear of coughing commuters, sneezing shoppers and ailing aunts. Hand sanitizer that contains at least 60 percent ethanol (also called ethyl alcohol) is very effective against flu.
Cold viruses on the remote
Are you constantly clicking between football and "A Christmas Story"? A 2011 study found that the TV remote is one of the germiest items in the house. Rhinoviruses, which cause about a third of all colds in adults, can be resistant to hand sanitizer and can survive on hard surfaces for four days. What to do: Wash your hands often, try not to touch your nose or eyes, and if you're really worried, hide the remote.
Bacteria at the buffet
Nasty bacteria called Clostridium perfringens cause about a million cases of food poisoning each year, and they can flourish in catered foods, especially meats, that sit out a long time. After two hours at room temperature, bacteria in food double every 20 minutes. What to do: At parties, pay attention to how long cooked food has been sitting. At home, refrigerate leftovers within two hours and freeze or toss them after three days.
Lice in Santa's lid
Pediculus humanus capitis isn't on anyone's wish list, but you're asking for it if you pop Frosty's old silk hat on your head without knowing where it's been. Lice don't hop or fly, so they have to be within crawling distance to hitch a ride. What to do: Wash suspicious items in hot water or seal them in a plastic bag for two weeks before wearing.
Salmonella with stuffing
You don't have to eat undercooked turkey to get a serving of salmonella. Raw eggs and poultry can leave microbes on utensils, hands and countertops, ready to spread to other food. What to do: Clean and sanitize as you cook. Use an eggnog recipe that requires heating the eggs. And don't bet on the booze in the eggnog: A 2008 experiment that suggested a 20 percent rum-and-bourbon concentration might kill salmonella was inconclusive.
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Sources: Partnership for Food Safety Education; USDA; CDC; J. Owen Hendley, professor of pediatrics and infectious diseases at the University of Virginia; Penn State University; Rockefeller University via ScienceDaily; Michigan Department of Community Health