The common cold and flu are caused by different viruses but can have some similar symptoms, making them tough to tell apart. In general, the flu is worse and symptoms are more intense.

COLDS: Usual symptoms include stuffy or runny nose, sore throat and sneezing. Coughs are hacking and productive. It's unusual to have fever, chills, headaches and body aches, and if they do occur, they are mild.

FLU: Fever is usually present, along with chills, headache and moderate-to-severe body aches and tiredness. Symptoms can come on rapidly, within three to six hours. Coughs are dry and unproductive, and sore throats are less common.

PREVENTION: To avoid colds and flu, wash your hands with warm water and soap after you've been out in public or around sick people. Don't share cups or utensils. And get a flu vaccination — officials say it's not too late, even in places where flu is raging.

TREATMENT: People with colds or mild cases of the flu should get plenty of rest and fluids. Those with severe symptoms, such as a high fever or difficulty breathing, should see a doctor and may be prescribed antiviral drugs or other medications. Children should not be given aspirin without a doctor's approval.

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Sources: U.S. Centers for Disease Control and Prevention; Roche, maker of Tamiflu.

Also: 5 foods that fight the cold and flu:

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  • Garlic

    Garlic's history as an infection fighter runs long (it was used as an antibiotic during both World Wars) thanks to the sulfur-containing compounds in each clove, <a href="http://apps.who.int/medicinedocs/en/d/Js2200e/4.html">including powerful allicin, ajoene and thiosulfinates</a>. The anitmicrobial effects of the garlic compound allicin are well-documented, including in <a href="http://www.allimax.us/Cutler.pdf">a 2004 study</a> in the <em>British Journal of Biomedical Science</em>, where researchers found the sulfinate effective against powerful, antibiotic resistant bacterial infections from Methicillin-resistant Staphylococcus aureus (MRSA). The medical literature consistently shows that <a href=http://www.ncbi.nlm.nih.gov/pubmed/10594976>allicin is also active</a> against drug-resistant E.coli infections, fungal infections (particularly oral and vaginal yeast infections), and parasites, including Giardia -- a common cause of traveler's diarrhea. Allicin also has antiviral properties. It's important to note that these findings have been on the cellular level in a lab setting, rather than observed from human diets. But at least one clinical trial found that dietary garlic was <a href=http://www.ncbi.nlm.nih.gov/pubmed/11697022>useful in preventing colds</a>. Allicin is only released when garlic cells are damaged (cutting, crushing, chewing) and is heat sensitive. Try adding some minced, raw garlic to a salad dressing.

  • Wheat Germ

    Wheat germ is one of the richest vegetarian sources of zinc -- an important mineral that is involved in nearly every aspect of immune system regulation. Zinc aids in the <a href="http://www.ncbi.nlm.nih.gov/pubmed/19519463" target="_hplink">development of T-lymphocytes</a>, a group of white blood cells that are central to fighting off infection. It also helps maintain healthy skin and mucus membranes -- the body's first barriers to infection. Wheat germ has 17 milligrams of zinc per 100 gram serving, more than the government's recommended daily allowance, <a href="http://ods.od.nih.gov/factsheets/Zinc-QuickFacts/" target="_hplink">which is 11 mg for men and eight for women</a>. Animal protein is the best, most bioavailable form of zinc -- particularly oysters, lobster, beef and pork shoulder. But not only are these sources also high in cholesterol and saturated fat, they are not an option for vegetarians, vegans and those who keep religious diets, like kosher and halal traditions. <a href="http://ods.od.nih.gov/factsheets/Zinc-QuickFacts/" target="_hplink"> According to the National Institutes of Health (NIH)'s Office of Dietary Supplements</a>, the reason grain-derived zinc is less available to humans than meat sources is because grains also contain phytates, a compound that binds to zinc and inhibits its absorption by the body. Soaking or sprouting the wheat germ before eating it will help to break down the phytates, improving zinc absorption.

  • Brazil Nuts

    Brazil nuts are the richest source of selenium, a nutrient that helps to form selenoproteins -- <a href="http://ods.od.nih.gov/factsheets/selenium">a powerful antioxidant that helps prevent cellular damage from free radicals</a>. That means selenium may help prevent chronic diseases like some cancers and heart disease, but selenoproteins also play a role in protecting the immune system by helping to form infection-fighting T-cells. One study in mice showed that the compound also <a href="http://www.ncbi.nlm.nih.gov/pubmed/21493887">helps regulate intestinal flora</a> -- helping gut bacteria to defeat invading pathogens. But Brazil nuts are <em>so</em> high in selenium that a single nut has nearly twice the recommended daily dose, as determined by the Institute of Medicine. While adults require 55 microgams per day, a Brazil nut has 95 mcgs -- and a single ounce has 544 mcgs. Too much selenium can be bad for your health, so it's better to consider the nuts an occasional dietary source rather than a daily one.

  • Mushroom Barley Soup

    Mushrooms and barley are both high in beta-glucan, a type of carbohydrate that's found on the cell walls of fungi, yeast, bacteria, algae, lichens, and plants. <a href="http://www.ncbi.nlm.nih.gov/pubmed/17161824">Researchers say that beta-glucan can stimulate the immune system</a> by mimicking an invading pathogen, which in turn improves the function of two types of immune defense cells: natural killer cells and macrophages, a type of white blood cell found in human tissue. And veterinary studies, <a href="http://www.ncbi.nlm.nih.gov/pubmed/15030604">including a 2004 experiment involving five-day-old piglets that had been exposed to swine influenza virus (SIV)</a>, have found that a daily dose of 50 mg of beta-glucan protected the treated piglets from the virus, compared to a control group that received placebo. While those studies used a beta-glucan extract rather than dietary beta-glucan, food sources of the compound -- particularly those found in mushrooms -- have been used to boost immune response by practitioners of folk and Eastern medicine for centuries.

  • Raw Kale Salad

    Raw kale is one of the best sources of vitamin C and has the added benefit of being low in sugar and high in fiber -- an overall healthy choice. Why raw? Vitamin C is <a href="http://www.nap.edu/openbook.php?record_id=9810&page=95">very sensitive to heat</a>, breaking down the nutrient and making it less effective. Stick to thinly cut ribbons of the veggie, which packs a bigger punch than salad greens. Each 100 gram serving of raw kale includes about 120 mg of vitamin C, well over the recommended dietary amounts for men (90 mg) and women (75 mg). Vitamin C, also known as ascorbic acid, is an antioxidant <a href="http://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional">that helps prevent cell damage caused by free radicals</a>. It is a very commonly used immune-boosting nutrient, though there is little clinical research that can explain how vitamin C helps boost immunity. But while studies prove that vitamin C won't help curtail a cold that's already in progress, observational data shows that people who have a vitamin C-rich diet tend to have shorter, more mild colds.

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