| What Is Influenza? |
At least 20 million people — 500,000 of them in the United States — died in the 1918 influenza pandemic. Today, as many as 20,000 Americans still die each year from what is commonly known as the flu. Another 200,000 are hospitalized. You're especially at risk if you're an older adult, have diabetes, chronic cardiovascular or lung disease, or an impaired immune system.
But anyone can get influenza, a viral infection that attacks your respiratory system, including your nose, throat, bronchial tubes and lungs. Although other viral infections, especially colds and intestinal ailments such as gastroenteritis — a condition that causes diarrhea, nausea and vomiting — are often referred to as the flu, they're not. Real influenza usually doesn't affect your intestines. And while you may cough and sneeze with the flu, you're also likely to have a high fever, chills and body aches — signs and symptoms you won't typically have with a cold.
You're exposed to the flu when someone who's infected with the virus coughs or sneezes, or you touch something they've handled. That's why the flu spreads rapidly anywhere people congregate — schools, child-care centers, offices, nursing homes, buses, even luxury cruise ships. Most outbreaks in North America occur between October and May. The peak season is usually late December to early March.
If you're at high risk of getting the flu, your first line of defense is an annual flu shot. For some people, antiviral medications taken within 24 to 48 hours of infection may help shorten the duration and intensity of symptoms slightly.
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| Signs and symptoms |
The flu virus attacks your respiratory system, especially your airways. This leads to the symptoms you commonly experience with the flu. Some signs and symptoms, such as a runny nose, sneezing and sore throat, may seem like a common cold. But if you have a fever of 101 F or more, it's more likely you have influenza. Your fever may last from 1 day to as long as a week and, in some cases, may reach as high as 106 F.
You're also likely to feel worse with the flu than with a cold. Although you can probably carry on with a cold, the flu can knock you flat. Even after you've recovered, you may still feel tired.
Other symptoms of influenza include:
- Chills and sweats
- Dry cough
- Muscular aches and pains, especially in your back, arms and legs
- Fatigue and weakness
- Nasal congestion
- Loss of appetite
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| Causes |
The flu is caused by three types of viruses — influenza A, B and C. Type A is responsible for the deadly influenza pandemics (worldwide epidemics) that strike every 10 to 40 years, while B causes smaller, more localized outbreaks. Type C is less common and causes only mild symptoms.
Type C is a fairly stable virus, but types A and B are constantly changing, with new strains appearing regularly. This results in a new epidemic every few years. Localized epidemics involving virulent strains of flu generally occur about every 3 to 15 years.
Once you've had the flu, you develop antibodies to the virus that caused it, but those antibodies won't protect you from new strains. And while outbreaks in different regions generally vary in their duration and severity, the fact that millions of people now travel every day means that regional strains of flu can show up just about anywhere.
| Risk factors |
The Centers for Disease Control and Prevention (CDC) suggests that children ages 6 months to 2 years and people older than 50 are at higher risk of complications from influenza and should receive an influenza vaccination.
In addition, you're at increased risk of influenza if you:
- Are a resident of a nursing home or other chronic-care facility.
- Have a chronic disorder such as diabetes or heart, kidney or lung conditions. People with diabetes
are at greater risk of complications of flu, such as pneumonia, and are 3 times more likely to die of
flu than people without diabetes.
- Have a weakened immune system from infection with the human immunodeficiency virus (HIV), leukemia
or medications you take following an organ transplant.
- Will be in your second or third trimester of pregnancy during flu season.
- Work in a health care facility where you're more likely to be exposed to the flu virus.
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Children are at high risk if they:
- Have asthma or another chronic lung condition.
- Have cardiovascular disease. Children with cardiovascular diseases may have a passive congestion
of their lungs, which makes them more susceptible to viral illnesses.
- Are taking medications to suppress their immune systems.
- Have sickle cell anemia, HIV infection, diabetes, chronic kidney disease, chronic metabolic diseases or are on long-term aspirin therapy. Aspirin therapy puts children age 16 and under at risk of Reye's syndrome, a rare, but potentially fatal, disease.
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The flu vaccine is safe for children 6 months or older. If your child isn't at risk of the flu but lives with someone who is — a grandparent, for instance, or anyone with a chronic heart or lung disease, or compromised immune system — you still may want to have your child vaccinated. That way, he or she is less likely to infect others. In fact, the more people who are immunized, the less likely it is that the infection will spread through a community.
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| When to seek medical advice |
See your doctor right away if you have flu symptoms, especially if you're at high risk of a severe case of influenza or complications of the disease. For some people, drugs known as neuraminidase inhibitors may help shorten the flu's duration and intensity. Other antiviral drugs, such as amantadine (Symmetrel), may help reduce the duration and severity of type A influenza, but may also cause side effects. To be effective, antiviral drugs need to be taken no later than 24 to 48 hours after you first notice symptoms.
In addition, seek medical help if you have trouble breathing, a severe sore throat, a cough that produces a lot of green or yellow mucus, or you feel faint. See your doctor immediately if you think you might have signs or symptoms of pneumonia. These may include a severe cough that brings up phlegm, a high fever and a sharp pain when you breathe deeply. If you have bacterial pneumonia, you'll need treatment with antibiotics.
| Complications |
If you're young and healthy, influenza is usually just a moderately severe illness. Although you may feel completely miserable while you have it, flu usually goes away with no lasting effects. But if you're 50 years of age or older or have a chronic illness, signs and symptoms can be much more serious and may lead to complications such as acute sinusitis, bronchitis or pneumonia. In some cases, flu can be fatal.
Pneumococcal pneumonia, a serious bacterial infection of your lungs, is the most common severe complication of influenza. For older adults and people with chronic heart or lung disease, or compromised immune systems, pneumonia can be deadly. The best protection is to be vaccinated against both pneumococcal pneumonia and influenza.
Some people may only need to receive the pneumonia vaccine once. Others, especially those with a serious underlying disease such as diabetes or who have had their spleen removed, may need to be vaccinated again in 6 to 10 years. Flu vaccines need yearly updates.
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| Treatment |
Unless you're at risk of complications from influenza, your doctor may suggest nothing more than bed rest and drinking plenty of fluids, so you don't become dehydrated. But in some cases, he or she may also prescribe an antiviral medication, such as:
- Neuraminidase inhibitors. These drugs, which treat both influenza A and B, work by
inactivating an enzyme the virus needs to grow and spread. Zanamivir (Relenza) was the first
neuraminidase inhibitor to reach the market and may shorten the amount of time you have the flu by a
day or two. Studies show it may also cut the risk of flu within a family when one family member is
infected. Relenza is inhaled through a device similar to an asthma inhaler every 12 hours for 5 days.
It shouldn't be used by anyone with respiratory conditions such as asthma and lung disease. Side
effects may include nose and throat discomfort, headache and cough. Another drug, oseltamivir
(Tamiflu) is available in pill form. It may also shorten the duration of the flu by a day or so.
- Oral antiviral medications. Drugs such as amantadine (Symmetrel) and rimantadine (Flumadine) may reduce the severity and duration of type A — but not type B — influenza if you take them within 48 hours after symptoms begin. But these medications may have serious side effects, including nausea, nightmares and convulsions. Taking lower doses of the drugs may reduce side effects.
| Prevention |
To help prevent any illness, eat right, get enough sleep, exercise regularly and wash your hands often. In the case of influenza, you can also protect yourself by getting a flu shot each fall. Flu shots need to be updated every year because the strains of viruses that cause the disease change frequently. In addition, if you're at high risk, try to avoid crowds when flu season is at its peak.
The best time to be immunized is between mid-October and mid-November. This allows your immunity to peak during the height of the influenza season, which is generally December through March. Adults receive the vaccine in one injection. Children under age 9 who are receiving the vaccine for the first time need two separate injections about a month apart. It takes 1 to 2 weeks after you've been vaccinated for the shot to take effect.
But the flu vaccine isn't foolproof. Its effectiveness varies from year to year and from one person to another. Since the strains used in the vaccine are chosen 9 months before a particular flu season, there's a slight chance the strains may change before the flu season actually starts.
In addition, if you're young and healthy, the vaccine may be 70 percent to 90 percent effective in preventing illness. But if you're an older adult or have a chronic medical condition, the vaccine may not be as protective. Still, for older adults who aren't at high risk, a flu shot can reduce hospitalizations by as much as 70 percent and deaths by 85 percent.
The CDC recommends flu shots for children ages 6 months to 2 years, for adults age 50 and older, and for anyone with an impaired immune system or a serious illness such as chronic heart or lung disease, kidney disease, diabetes, or sickle cell anemia. You should also be vaccinated if you're a health care worker, police officer or firefighter.
You may worry about contracting flu from the vaccine. But the vaccine has an inactivated form of the virus, so you can't get the flu from a flu shot. In some cases, however, you may have a slight reaction to the shot, such as soreness at the injection site, mild muscle aches or fever beginning 6 to 24 hours after you've been immunized. These symptoms may last 1 or 2 days and are more likely to occur in children who've never been exposed to the flu virus.
If you're allergic to eggs, you probably shouldn't have a flu shot. Because the viruses are grown in chicken eggs, you may have an allergic reaction. If you're pregnant, wait until after your first trimester to be immunized, unless your doctor advises you otherwise.
In addition to getting a flu shot from your doctor, you can be vaccinated at public health centers and many pharmacies. In some areas, flu shots are also available at senior or community centers.
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| Self-care |
If you do come down with the flu, these measures may help ease your symptoms:
- Drink plenty of liquids to avoid dehydration.
- Get more sleep.
- Try chicken soup. It's not just good for your soul — It really can help relieve flu symptoms by
breaking up congestion.
- Use an over-the-counter pain reliever such as acetaminophen (Tylenol, generics) or ibuprofen (Advil, Motrin) cautiously, as needed. Remember, pain relievers won't make your symptoms go away any faster and may have serious side effects. Ibuprofen may cause stomach pain, bleeding and ulcers. If taken for a long period of time or in high doses, acetaminophen can be toxic to your liver. Talk to your doctor before giving acetaminophen to children — It may cause liver or kidney damage. And don't give aspirin to children under age 16 because of the risk of Reye's syndrome, a rare, but potentially fatal, disease.
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— October 1, 2002 —