The winter months present plenty of opportunities for viruses to spread. Chilly weather keeps more of us indoors at the same time, and the holiday season brings together family members of all ages. Colds and flu (influenza) can occur anytime, but appear mostly in the fall and winter.

Flu season in the United States runs from November to April. October to November is the usual vaccination time for most people. "But you can also get good results when the vaccine is used in December and January, even if influenza is already starting to spread through a community," says Roland A. Levandowski, M.D., a medical officer and virologist in the Food and Drug Administration's Center for Biologics Evaluation and Research. We need a new flu shot every year because the predominant flu viruses change every year.

The protective effect of the vaccine starts working rapidly in people who have been previously infected with flu viruses or have received a flu shot in the past. Infection-fighting antibodies in the blood reach a peak about three weeks after these people get the shot. But for some, such as children younger than 9 who haven't been previously vaccinated, two doses of the influenza vaccine about a month apart are recommended for the first vaccination. In older people and in those with chronic illnesses, the shot may not necessarily prevent the flu, but can reduce the symptoms and risk of complications if they do get sick.

The flu vaccine is made of killed virus and can't cause the flu. The most common side effect is soreness at the injection site. The flu shot is not recommended for certain people, including those allergic to eggs. The viruses for flu vaccines are grown in eggs.

In June 2003, the FDA approved FluMist, the first nasally administered flu vaccine to be marketed in the United States. The needle-free vaccine is for healthy children and adolescents ages 5 to 17 and in healthy adults ages 18 to 49. The nasal spray is manufactured by MedImmune Vaccines Inc. of Gaithersburg, Md., and is marketed by MedImmune and Wyeth Vaccines of Philadelphia.

FluMist is also the first live virus influenza vaccine to be approved in the United States. The most common side effects are nasal congestion, runny nose, sore throat, and cough. As with other live virus vaccines, FluMist should not be given to people with suppressed immunity, such as people with AIDS or cancer. The vaccine also shouldn't be given to pregnant women, people with a history of asthma or other reactive airway diseases, people age 50 and over, or to children under 5.

Wash your hands.

Both colds and flu can be passed through coughing, sneezing, and touching surfaces such as doorknobs and telephones. So it's wise to make a habit of washing your hands and to teach children to do the same. This helps you prevent spreading respiratory infections and picking them up from someone else.

According to the American Society for Microbiology, a national survey found that Americans were most likely to say they wash their hands after changing a diaper and before handling food. Most, however, said they don't wash their hands after coughing and sneezing.

The CDC recommends regular scrubbing of your hands with warm, soapy water for about 15 seconds. Touching your nose, mouth, and eyes with contaminated hands makes it easy for cold and flu viruses to enter the body. Others can become ill by just coming in contact with someone who has become infected with a cold or flu virus or who has come in contact with a contaminated area.

Limit exposure to infected people.

Sometimes people are infected with a virus and they don't know it because they haven't experienced symptoms yet. If possible, avoid people who you know have colds and flu. Keep infants away from crowds for the first few months of life. "This is especially important for premature babies who may have underlying abnormalities like lung disease and heart disease," says Larry Pickering, M.D., a fellow of the American Academy of Pediatrics and a pediatrician in Atlanta.

If keeping your distance is too difficult--say in the case of parents who can't help but hold and kiss their sick kids--then, in addition to washing your hands frequently, you can keep surfaces clean with a virus-killing disinfectant available at the grocery store. A solution of 1 part bleach mixed with 10 parts water also is effective in killing viruses.

Practice healthy habits.

Eating a balanced diet, getting enough sleep, and exercising can help the immune system better fight off the germs that cause illness. Because smoking interferes with the mechanisms that keep bacteria and debris out of the lungs, those who use tobacco or who are exposed to secondhand smoke are more prone to respiratory illnesses and more severe complications than nonsmokers.

If you've been feeling run down, some stress management might not be a bad idea. David Skoner, M.D., chief of allergy and immunology at Children's Hospital in Pittsburgh, has studied the effects of chronic stress on susceptibility to cold and flu infections. "We've found that people who experience more stress are more likely to get sick and experience worse symptoms," he says. Examples of chronic stress are personal crises such as going through a divorce or feeling stuck in a bad job.

"Research has also shown that the more social you are, the less likely you are to get sick," Skoner says. It could be because having more social contacts and support is less stressful than keeping to yourself, he says.

If you do come down with a cold or flu, here's advice on safe relief from symptoms:

Drink up and rest.

Fluids such as water, juice, soup, and non-caffeinated beverages can help loosen mucus, keep you hydrated, and make you feel better, especially if you have a fever. Alcohol and drinks containing caffeine may have a dehydrating effect. To help others stay healthy, limit your exposure to them and promptly throw out tissues rather than letting them pile up on your nightstand.

Gargling with salt water can help relieve a sore throat. A cool-mist humidifier, which breaks water into droplets and releases them into the air, may help relieve stuffy noses. Keep the humidifier clean to avoid a buildup of mold, which could be harmful if inhaled. Saline nasal drops and suctioning with a bulb syringe can help infants and small children breathe better. But be gentle because aggravating the nasal passages could make swelling worse. Also, dress sick children comfortably--like you would dress yourself, Pickering says. "Some parents bundle them up if they have a fever, but that can make it worse."

Choose over-the-counter (OTC) medicines that are appropriate for your symptoms.

With all the choices on the shelves, it can be hard to know what medicine to pick. It may seem easier to grab a multi-symptom medicine that promises to take care of everything, but it's better to take a product specific to your symptoms, says Jeffrey Delafuente, a professor and director of geriatric programs at Virginia Commonwealth University's School of Pharmacy.

"If your only problem is a runny nose, why take a cough suppressant?" he says. Taking medicine for symptoms you don't have may not be harmful, he adds, but it unnecessarily exposes you to medicine and the accompanying side effects. "Multi-symptom medicines can be useful if you truly have many symptoms."

If you want to unclog a stuffy nose, then nasal decongestants may help. Cough suppressants quiet coughs; expectorants loosen mucus so you can cough it up; antihistamines help stop a runny nose and sneezing; and pain relievers such as acetaminophen can ease fever, headaches, and minor aches. Check with a pediatrician or your family physician first before treating children suffering from cold and flu symptoms with medicine.

Don't give aspirin or aspirin-containing medicines to children and teen-agers.

Children and teen-agers suffering from flu-like symptoms, chickenpox and other viral illnesses shouldn't take aspirin because of the possibility of Reye syndrome. Some medicine labels may refer to aspirin as salicylate or salicylic acid. Be sure to educate teen-agers, who may take OTC medicines without their parents' knowledge.

Children with Reye syndrome start vomiting and become drowsy within a few days of becoming sick. The disorder, which is now rare, can affect all body organs and lead to brain damage and death. Reye syndrome occurs almost exclusively in children 4 to 12 years of age and is rare in adults, Pickering says.

Read OTC medicine labels carefully and follow directions.

Use the dosing device that comes with the medicine and don't exceed recommended dosages or length of use. Taking a nasal spray for too long during a cold could result in an even stuffier nose, for example. Always check with a doctor first if the correct dose for a child isn't listed on a label and before giving a child more than one medicine at a time.

Delafuente says he tells older people, who often take multiple medications, to check with a doctor or pharmacist before taking a new OTC cough and cold medicine because some can worsen underlying health problems, such as high blood pressure or heart disease. Decongestants can speed up heart rate, for example, and antihistamines can cause urinary retention in men with prostate problems. For both young and old, antihistamines can make you drowsy, which could affect driving.

Be sure to check expiration dates and get rid of old medicine. The FDA has warned consumers against using OTC and prescription drug products containing phenylpropanolamine because the ingredient has been associated with an increased risk of hemorrhagic stroke (bleeding in the brain). This ingredient was commonly used as a decongestant in OTC and prescription cough and cold medicines before the warning.

Be careful not to double up on ingredients.

If you take more than one medication at a time, be careful not to duplicate ingredients, says Marina Chang, a pharmacist with the FDA's Center for Drug Evaluation and Research. "Look at the active ingredients of every medicine you take," she says.

For example, you don't want to accidentally take two different medicines that both contain acetaminophen. The same goes for taking acetaminophen tablets to relieve pain while also taking a cough medicine containing acetaminophen. Too much of this drug can result in liver damage.

Jon Temte, M.D., Ph.D., associate professor of family medicine at the University of Wisconsin Medical School, recalls a young woman who came in complaining of a racing heartbeat and anxiousness. He discovered her symptoms occurred because she had taken two different products, both containing a decongestant.

Facts About Flu Drugs.

Relenza (zanamivir) and Tamiflu (oseltamivir), both approved for use in 1999, are to treat uncomplicated cases of influenza caused by types A and B flu virus. Tamiflu also is approved for preventive use, while Relenza is approved only for treatment. Two older drugs, amantadine and rimantadine, which are sold under the trade names Symmetrel and Flumadine respectively, are approved for the treatment and prevention of Type A influenza.

Talk with your health care provider about any use of these drugs in children. The doses and approved ages are different for each. Because some of the drugs' side effects can be serious and because viruses may become resistant when antiviral drugs are used indiscriminately, the FDA recommends that decisions to use these drugs be based on individual evaluations of risk and benefit.

Relenza, which is orally inhaled as a dry powder with a device known as a Diskhaler, can cause wheezing or serious breathing problems, and is generally not recommended for patients with asthma, chronic obstructive pulmonary diseases and other airway diseases.

Common side effects of Tamiflu, which comes in pill and liquid form, include nausea and vomiting. Both amantadine and rimantadine can cause gastrointestinal side effects and central nervous system changes such as nervousness and difficulty concentrating. Other side effects that can occur are mentioned in the drugs' package inserts.

Other important flu drug facts:

• Antiviral drugs are not meant to take the place of a flu shot. The flu shot remains the best way to protect yourself. The drugs are sometimes used as a backup to the vaccine in special situations, such as to control a flu outbreak.
• The treatment effect of these drugs is modest. They won't make you instantly better, but can help shorten the time the flu lasts by about a day. And use of flu drugs does not eliminate the risk of flu complications.
• The drugs are meant to be taken within the first two days you experience flu symptoms. That means if you arrive at the doctor's office on Day 5 asking for a flu drug, you'll be too late. By that time, uncomplicated flu usually starts to get better on its own, and people who develop complications are likely to need other treatment.
• Flu drugs don't influence bacterial infections or other illnesses that may look like the flu. It's important to talk with your health care provider if you are being treated with an antiviral drug but aren't getting better or if you experience new symptoms.

Michelle Meadows is a staff writer for FDA Consumer.

Cold and Flu Symptoms

People who get the flu usually know the exact day that it hit, whereas a cold tends to come on gradually. Both colds and flu cause inflammation of the mucous membranes (found in the nose, throat and mouth). Symptoms for colds and flu can be similar; both can cause a stuffy nose, sore throat, cough, and fever. Symptoms generally last about a week or two.

Colds are usually distinguished by a runny nose and sneezing. Along with coming on suddenly, the flu is more serious than a cold, lasts longer, and often leaves you with a wiped-out feeling, a headache, chills, dry cough, and body aches.

Young children may also experience nausea and vomiting with flu, but what many people call "stomach flu" is something different--probably gastroenteritis, which is usually caused by other viruses, bacteria, and toxins.

When You Need a Doctor

Jerry Rogers, M.D., a family physician in Moorhead, Minn., says some patients have asked him about taking an antibiotic early on, before their cold or flu symptoms get bad. But antibiotics don't help viral illnesses. Using antibiotics inappropriately only spreads antibiotic-resistant bacteria, making fewer drugs effective for treating disease.

Most of the time, colds and flu simply have to run their course. "We don't typically treat colds and flu unless they become complicated," Rogers says. You usually don't need to call the doctor at the first signs of cold and flu, but there are times when you should.

Doctors will look for and treat cold and flu complications such as bronchitis, sinusitis, ear infections, and pneumonia--bacterial infections that may require antibiotics. For some people, colds and flu can aggravate underlying medical conditions like heart disease and asthma.

If you aren't getting any better after about a week or your symptoms worsen, you should see a doctor. Your viral infection may have caused enough mucus buildup to allow for a bacterial infection to occur. Signs of trouble might be a cough that gets so bad it disrupts sleep, a fever that won't go down, increased shortness of breath, and pain in the face because of a sinus infection (sinusitis).

Another warning signal is if after feeling better for a short time you start to feel worse and experience a high fever, chest pain, or notice a difference in the mucus you're producing, such as a change from clear to thick, yellow-green mucus.

With children, be alert for high fevers and abnormal behavior--acting unusually drowsy, refusing to eat, crying a lot, holding the ears or stomach, and wheezing.

Unproven Remedies

Some people rely on vitamin C supplements, zinc lozenges, and echinacea to prevent and treat cold and flu symptoms. These remedies may make some people feel better. However, their health effects are unknown, says Linda Lambert, a program officer with the National Institute of Allergy and Infectious Diseases (NIAID).

No conclusive data has shown that large doses of vitamin C prevent colds; they may reduce the severity or duration of symptoms, but there is no definitive evidence. And the jury is still out on zinc. "There are about an equal number of studies that say zinc helps as there are studies that say it doesn't," Lambert says.

As for echinacea, "studies have been done of echinacea for preventing or treating colds and flu, but these studies were not rigorous or definitive and the products tested were diverse," according to a written statement from Stephen Straus, M.D., director of the National Center for Complementary and Alternative Medicine, part of the National Institutes of Health. "These studies at best suggest that echinacea may be beneficial in the early treatment of colds and flu, but does not help prevent them."

Always tell your doctor about any supplements or herbal remedies you use, and don't overdo it. For example, taking too much vitamin C can cause diarrhea.

Primary Target Groups for Flu Vaccination

The best time to get a flu vaccination is from October through November, and people who have a high risk of complications from flu should be vaccinated starting in September, according to the Centers for Disease Control and Prevention.

The CDC strongly recommends annual flu vaccination for these primary target groups:

Unvaccinated high-risk persons, health-care workers, those living with high-risk people, and all people ages 50 and older should try to be vaccinated by November, and should continue to seek influenza vaccine in December or later if necessary.

Here are the primary target groups for annual flu vaccination:

People at increased risk for complications from the flu, including

• people 65 and older
• residents of nursing homes and other facilities that house people who have chronic medical conditions such as diabetes, asthma, and heart disease
• adults and children who have chronic pulmonary or cardiovascular disorders, including asthma
• adults and children who have required regular medical follow-up or hospitalization during the preceding year because of chronic metabolic diseases (including diabetes), kidney dysfunction, disorders caused by hemoglobin abnormalities, or a weakened immune system, including immunosuppression caused by medications or the virus that causes AIDS
• children and teen-agers (ages 6 months to 18 years) who are receiving long-term aspirin therapy, and therefore might be at risk for developing Reye syndrome
• women who will be in the second or third trimester of pregnancy during the flu season.

People who can transmit influenza to those at high risk

• physicians, nurses, and other personnel in hospital and outpatient care settings, including emergency response workers
• employees of nursing homes and chronic-care facilities who have contact with patients or residents
• employees of assisted living and other residences for persons in high-risk groups
• persons who provide home care to persons in groups at high risk
• household members (including children) of people in groups at high risk.

People ages 50-64 because this group has increased prevalence of high-risk conditions.