It begins simply: A few sneezes, a scratchy throat, stuffed nose and that sinking feeling that marks the beginning of yet another cold.

Most people suffer three to five colds each year -- about 300 in the course of an average lifetime -- many of which occur around the time of the Christmas holidays, a peak season for colds.

Children, who are least immune to infections, average six colds annually, while the elderly, who can draw upon decades of immunity, suffer only one or two. Each cold lasts about seven days, which over a lifetime adds up to almost six years spent hacking, wheezing and sniffling.

While science has been virtually powerless to do much to prevent or treat this most common, harmless and annoying of human illnesses, the good news is that researchers have made recent advances in deciphering the precise ways in which colds wreak such misery. Some of the genes in the nearly 200 viruses that cause colds have been identified and reproduced in the laboratory, leading to the development of two new, but so far experimental, classes of drugs.

The bad news is that researchers say these cold-fighting drugs are years away from pharmacy shelves. For now, cold sufferers have little choice but to suffer through about a week of sneezing and coughing. A Chill Is Not Enough

Most people are convinced that they can pinpoint when and how they caught a cold, usually after getting chilled, for example by sitting in a numbing 30-degree drizzle watching the Redskins play at RFK Stadium. In fact, this is a myth ingrained in childhood. There isn't a shred of scientific evidence that not wearing a hat outside or getting caught in a freezing downpour is responsible for a subsequent cold.

"Science has tried hard and failed to confirm any effect of getting cold or chilled on developing the common cold," said Robert Couch, chairman of the Department of Microbiology and Immunology at Baylor College of Medicine in Houston.

Sir Christopher Andrews, a British physician and co-discoverer of the first influenza virus, tested the chill theory in 1951. Using a group of volunteers who were soaked from walking in the rain, Andrews then had them sit in a drafty, unheated hallway in their wet underwear for hours. None developed a cold. Even when the experiment was repeated and the volunteers were experimentally infected with cold virus, they still developed no more infections than a control group, which was also infected but had not gotten chilled.

The only way to catch a cold is by becoming infected with one of the hundreds of cold viruses that turn perfectly normal nasal passages into a clogged nightmare. Scientists believe that infections occur two ways: by hand-to-hand contact and by microscopic aerosolized particles that linger in the air after a cold sufferer coughs or sneezes. Which route is more important is debatable.

There's evidence for both. Sneezing into a handkerchief releases thousands of viruses, some of which also coat the hand. In studies, cold viruses have been recovered from the hands of 40 to 90 percent of adults with colds, who also managed to contaminate up to 15 percent of the room around them. Cold viruses can survive on countertops and skin for hours, waiting to be transmitted to an unsuspecting individual. The person whose hand brushes a contaminated area, then rubs an eye or picks up a piece of candy may inadvertently become infected. Such infection occurs routinely, although most people get sick only occasionally because their immune systems are able to ward off cold viruses.

Kissing a cold sufferer may not be as risky as traditionally believed. In a 1970 experiment, University of Wisconsin cold researcher Elliott Dick and his colleagues had people suffering from colds plant sloppy, 90-second kisses on the lips of volunteers. Only one of the 13 volunteers developed a cold.

At the same time, handwashing remains an important protection against colds. "We share doorknobs, currency and hang on the Metrorail together," said David Fairbanks, a Fairfax County physician who is the spokesman for the American Academy of Otolaryngology, an association of ear, nose and throat specialists. "Unless you become a hermit, you will get a few colds from hand-to-hand contact."

But whether hand contact is the chief way colds are spread is uncertain. Some scientists believe that infection by aerosol particles is a more efficient method of contracting a cold.

Colds and flu spread rapidly in the winter partly because more people spend more time indoors in close quarters, breathing the same air. Dry, air-tight, energy-efficient buildings and homes provide the perfect medium for colds to move from person to person.

Several studies at the University of Wisconsin illustrate how airborne transmission occurs. Researchers recruited a total of 20 volunteers, infected them with a cold virus, then sequestered them in a room where they were instructed to play poker with uninfected people. Four uninfected volunteers -- or two thirds of that group -- got colds.

An experiment conducted at the same time gauged the role of hand-to-hand contact. Uninfected volunteers wore splints on their arms that enabled them to play poker but prevented them from touching their faces and contaminating mouths, noses or eyes with cold virus. Even so, more than half of the uninfected volunteers in that group -- three people -- developed colds. That's a slight but not statistically significant decrease, Dick said.

In a third experiment, Dick had cold sufferers play poker for hours, then passed the sticky, contaminated cards to an uninfected group of players in a separate room. Each hour during a night-long marathon poker game, the uninfected volunteers received a newly contaminated deck of cards and poker chips. Not one of them developed a cold. "Our results suggest that it is extremely difficult to spread colds by hands," said Dick.

Regardless of how they are transmitted, colds appear to be most contagious when symptoms are worst. According to studies conducted at the University of Virginia, the third day of an average cold is generally the most miserable, and that's also the time when the most virus particles are produced by an infected individual.

Cold viruses are also affected by the seasons. During fall or spring, rhinoviruses predominate, and more than 100 strains are believed to account for about half of all the colds contracted by adults.

Next comes parainfluenza, a cold virus that can also cause croup, a bark-like cough, in children and laryngitis in adults. In mid-December, the coronaviruses appear. They are the second leading cause of colds and account for about 10 percent of all annual infections.

Technically, a slew of viruses can produce cold symptoms at any time of year. The only definitive way to tell which one is causing a cold is to undergo a nasal culture.

"It's sort of a moot point," said Stephen Mitchell, a Texas physician who chairs the American Academy of Otolaryngology's committee on speech, voice and swallowing disorders. "By the time you find out the results, you'll be well."

Cold viruses are difficult to identify by symptoms alone because one strain can have different effects. "It can cause a {symptom-free} infection in one person, a bothersome cold in someone else, and an ear infection in one of your children," said Kathryn Holmes, a virologist who studies colds at the Uniformed Services University of the Health Sciences in Bethesda.

That's why comparing symptoms with an office mate who was sick recently is likely to provide inaccurate information about the future course of a cold.

Distinguishing a cold from the flu is difficult without a culture, a test doctors usually regard as unnecessary. For most people, both infections are self-limiting and relatively harmless. "Anything that stays in your nostrils and in the upper airways is a cold," said John R. La Montagne, director of the division of microbiology and infectious diseases at the National Institute of Allergy and Infectious Diseases.

An illness accompanied by a high fever, chills and wretched aching "is probably not a cold," he added.

When an infection moves to the larynx or to the lungs, it becomes potentially more serious and may signal the flu or a secondary bacterial infection, such as bronchitis. Smoking worsens cold symptoms and increases the likelihood of complications. Stress also plays a role, since studies show that it helps weaken the immune system.

One sign of a secondary bacterial infection is when phlegm or nasal secretions turn from clear to yellow or green. "If you have pain in the cheeks, or between, above or around the eyes or in the upper teeth, that's a sign of bacterial infection, and the time to consult your doctor," said Fairbanks, the Northern Virginia ear, nose and throat specialist.

There's an age-old adage: treat a cold and it goes away in a week. Do nothing and you'll be cured in seven days. Contrary to popular belief, antibiotics are useless against both colds and flu, because they fight only bacterial infections, which do not cause colds or flu.

There are, of course, an array of over-the-counter medications to counter the range of symptoms with cough suppressants and expectorants, nasal decongestants, antihistamines and pain relievers. The most common ingredients in over-the-counter cold medications include dextromethorphan, which suppresses coughs; chlorpheniramine, an antihistamine used to shrink nasal passages and dry a drippy nose, and phenylpropanolamine, a decongestant that helps unclog stuffy noses and shrinks nasal membranes.

Many doctors now recommend that consumers choose products that contain just one or two drugs. The reason: concern about possible drug interactions from products with multiple ingredients.

Cold and cough medications are big business, accounting for about $2.4 billion in sales annually, according to Kline & Co., an international business consulting firm in Fairfield, N.J. Whether they work is debatable. Some doctors, among them Sidney M. Wolfe, director of the Public Citizen Health Research Group, say that drugs are unnecessary in battling colds and that some may in fact prolong them. "The safest, best and least expensive way to care for a cold is to not take anything at all and let the illness run its short, frequently self-limiting course," he and his colleagues wrote in their book, "Best Pills, Worst Pills."

For those with medical problems such as high blood pressure, some cold medications can be dangerous. Many contain ingredients that constrict blood vessels, an action that can send blood pressure soaring and pose particular hazards for those whose blood pressure is already high. Pregnant women are also warned against taking any medications, including nonprescription cold products, without consulting a doctor. Children under 16 are no longer given aspirin, because of the danger of Reye's syndrome -- a fairly rare but potentially fatal neurological complication.

For most people, cold medications won't hurt anything but their wallets. And there's some new research to suggest that one ingredient, the common decongestant pseudoephedrine found in Sudafed, may "indeed make individuals with rhinovirus colds somewhat better," said Couch of Baylor.

All pain relievers need to be used judiciously. A report published in the December issue of the Journal of Infectious Diseases says that aspirin and acetaminophen, increased the severity of some cold symptoms and reduced infection-fighting antibodies. The study by Johns Hopkins researchers found that a third over-the-counter drug, ibuprofen, did not worsen symptoms or depress the immune system.

Another agent that's getting a closer look is vitamin C, a substance long promoted by the Nobel-prize-winning scientist Linus Pauling as an important weapon in preventing and moderating colds. Pauling's claims have been hard to document in scientific studies, a fact that has made the use of vitamin C in cold prevention controversial.

Preliminary findings of research at the University of Wisconsin are renewing interest in vitamin C. Presented this fall at the Inter-Science Conference on Antimicrobial and Chemotherapy Agents, the studies found that vitamin C produced milder colds. But the doses required are high -- at least two grams per day -- a level that could irritate the stomach lining and should not be taken by people prone to kidney stones.

Dick, the researcher who conducted the experiment, has now devised his own vitamin C regimen, which he believes is effective in preventing colds. He takes two grams when he feels cold symptoms coming on, then two more grams an hour later, followed by a gram each hour until the symptoms are gone.

There are of course, a score of other popular remedies: chicken soup, steaming showers, hot lemonade, tea with honey and lemon, and eucalyptus chest rubs. No one knows whether these actually work, because none has been tested in controlled scientific trials.

In theory, some of them may help. "If you're drinking something warm and elevating the temperature of the upper airways for a sufficiently long enough period of time, you might in fact do something to interfere with the replication of the virus," said NIAID's La Montagne.

Drinking lots of fluids helps to relieve some of the symptoms of colds, although it won't make them go away faster. Between a pint to a quart of liquid is lost through nasal secretions, the reason that you need extra fluids to counter dehydration. That's why, as comforting as it may sound, a hot toddy or other form of alcohol is a bad idea and may make you feel worse because alcohol speeds dehydration. Elevating the head on several pillows while sleeping may help drain clogged nasal passages and keep sinuses from blocking.

The bottom line, said Owen Hendley, a colds researcher at the University of Virginia, is -- "if it makes you feel better, take it."