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This article is from the In-Depth Report A Guide to Swine Flu

What's the difference between cold and flu?

The two winter respiratory illnesses may look alike, but pay attention to tell them apart



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How many times have you dismissed sniffles as "just a cold," and carried on with a stuffed nose and sinuses assuming that the symptoms would eventually run their course, perhaps a bit more quickly with a few doses of Mom's homemade chicken soup?

Influenza is another story. The common cold eventually fizzles, but the flu may be deadly. Some 200,000 people in the U.S. are hospitalized and 36,000 die each year from flu complications — and that pales in comparison to the flu pandemic of 1918 that claimed between 20 and 100 million lives. The best defense against it: a vaccine. Yet barely 30 percent of 4,000 U.S. adults surveyed said they'd been inoculated this season, despite a record supply of flu shots, according to a new RAND Corp. survey. (GlaxoSmithKline, which makes flu vaccine, helped pay for the survey.)

So what is the difference between a cold and the flu – and how can you be sure which one you have?

We asked Jonathan Field, director of the allergy and asthma clinic at N.Y.U. Langone Medical Center/Bellevue Hospital in New York. Following is an edited transcript of our interview with him.

What causes the flu? How is it different from a cold?

The flu is a viral infection caused by the influenza virus, a respiratory virus. The common cold is also a viral infection caused by the adenovirus or coronavirus and there are many, many subsets with a lot of variability. That’s why it's said there's no cure for the common cold [and] there's no real vaccine. The flu is known to be from influenza and is preventable with vaccination.

Colds tend to produce runny nose, congestion, sore throat. Influenza is more pronounced in that it infects the lungs, the joints and causes pneumonia, respiratory failure and even death. It tends to infect the intestinal tract more in kids, with diarrhea and vomiting. Because of the relative immaturity of the gut, they may absorb more virus and that wreaks more havoc on the intestines. Flu causes epidemics and pandemics with the potential for mortality, whereas the common cold is a nuisance for us.

How can someone who's feeling ill distinguish between cold and flu, or an allergy?


Flu typically starts in early November and can go until March. The peak time is now — November to January. Allergy is typical in spring or fall, and cold more so in winter.

The body can respond in only so many ways, but there are things you can use to differentiate. Allergic symptoms are similar to those of a cold, but [result from] your immune system responding to something benign. Usually there's no fever, and there's an allergic manifestation of itch in the back of the throat or the ears. It's unlikely with allergy to have body aches. With a cold, there's sometimes a low-grade fever.

You can tell the difference by the length and severity of the illness and whether you've had a similar experience in the past. Both colds and flu usually last the same seven to 10 days, but flu can go three to four weeks; the flu virus may not still be there, but you have symptoms long after it's left. Allergy can last weeks or months.

Are the treatments for these illnesses different?


For any of these things, if it affects the nose or sinus, just rinsing with saline that gets the mucus and virus out is a first-line defense. It's not the most pleasant thing to do, but it works very well. There are classes of medicines that can help the flu — Tamiflu and Relenza — antivirals that block viruses' ability to reproduce and shorten the length and severity of the illness. But they have to be taken within 48 hours or the cat is proverbially out if the bag [because by then] the virus has done the most of its reproduction. For a cold or flu, rest and use decongestants and antihistamines, ibuprofen, acetaminophen, chicken soup and fluids.

Zinc supposedly helps the body's natural defenses work to their natural capacity and decrease the severity and length of a cold. Cells need zinc as a catalyst in their protective processes, so if you supply them with zinc, it helps them work more efficiently. You should also withhold iron supplements. Viruses use iron as part of their reproductive cycle, so depriving them of it blocks their dissemination.

The majority of these infections are not bacterial and do not require [nor will they respond to] antibiotics. My rule of thumb is that a viral infection should go away in seven to 10 days. If symptoms persist after that, you'd consider if it's bacteria like Strep or Haemophilus influenzae. Those bacteria cause illnesses that are longer lasting.

Is that treatment approach the same for kids?

In general, the same rules apply: Most children will have six to eight colds a year in their first three years of life, and most are viral. It's very easy to test for strep and for that you should have a [positive] culture [before treating with antibiotics].

Are the strategies for avoiding cold and flu different?

Avoidance is very similar: Strict hand washing, not sharing drinking cups or utensils, and avoiding direct contact with people who are sneezing. As long as someone has a fever, they have the possibility to transmit infection. After they've had no fever for 24 hours, they're not infectious.

The U.S. Centers for Disease Control and Prevention (CDC) now recommends that just about everyone get the flu shot: kids 6 months to 19 years of age, pregnant women, people 50 and up, and people of any age with compromised immune systems. Is the shot beneficial to anyone who gets it?

Unless you have a contraindication, there's no reason not to get it. Contraindications would include egg allergy (because the vaccine is grown from egg products), any vaccines within a last week or two, and active illness at the time of your vaccine.

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