Public Health

People age 65 years and older, people of any age with chronic medical conditions, and very young children are more likely to get complications from influenza. Pneumonia, bronchitis, and sinus and ear infections are three examples of complications from flu. The flu can make chronic health problems worse. For example, people with asthma may experience asthma attacks while they have the flu, and people with chronic congestive heart failure may have worsening of this condition that is triggered by the flu.

How the Influenza Virus Is Passed Around The flu is spread, or transmitted, when a person who has the flu coughs, sneezes, or speaks and sends flu virus into the air, and other people inhale the virus. The virus enters the nose, throat, or lungs of a person and begins to multiply, causing symptoms of influenza. Influenza may, less often, be spread when a person touches a surface that has flu viruses on it - a door handle, for instance - and then touches his or her nose or mouth.

The Flu Is Contagious A person can spread the flu starting one day before he or she feels sick. Adults can continue to pass the flu virus to others for another three to seven days after symptoms start. Children can pass the virus for longer than seven days. Symptoms start one to four days after the virus enters the body. Some persons can be infected with the flu virus but have no symptoms. During this time, those persons can still spread the virus to others.

How To Know if You Have the Flu Your respiratory illness might be the flu if you have sudden onset of body aches, fever, and respiratory symptoms, and your illness occurs during November through April (the usual flu season in the Northern Hemisphere). However, during this time, other respiratory illnesses can cause similar symptoms and flu can be caught at any time of the year. It is impossible to tell for sure if you have the flu based on symptoms alone. Doctors can perform tests to see if you have the flu if you are in the first few days of your illness.

What You Should Do If You Get the Flu - Rest
- Drink plenty of liquids
- Avoid using alcohol and tobacco
- Take medication to relieve the symptoms of flu
- Influenza is caused by a virus, so antibiotics (like penicillin) don`t work to cure it. Your physician may want to prescribe an antiviral medication.

Do Not Give Aspirin To a Child or Teenager Who Has the Flu Never give aspirin to children or teenagers who have flu-like symptoms - and particularly fever - without first speaking to your doctor. Giving aspirin to children and teenagers who have influenza can cause a rare but serious illness called Reye syndrome. Children or teenagers with the flu should get plenty of rest, drink lots of liquids, and take medicines that contain no aspirin to relieve symptoms.

The Myth of the "Stomach Flu" Many people use the term "stomach flu" to describe illnesses with nausea, vomiting, or diarrhea. These symptoms can be caused by many different viruses, bacteria, or even parasites. While vomiting, diarrhea, and being nauseous or "sick to your stomach" can sometimes be related to the flu these problems are rarely the main symptoms of influenza. The flu is a respiratory disease and not a stomach or intestinal disease.

Groups At Risk for Complications from Influenza A yearly flu shot is recommended for the following groups of people who are at increased risk for serious complications from the flu:
- persons aged >50 years;
- residents of nursing homes and other long-term care facilities that house persons of any age who have long-term illnesses;
- adults and children > 6 months of age who have chronic heart or lung conditions, including asthma;
- adults and children > 6 months of age who need regular medical care or had to be in a hospital because of metabolic diseases (like diabetes), chronic kidney disease, or weakened immune system (including immune system problems caused by medicine or by infection with human immunodeficiency virus [HIV/AIDS]);
- children and teenagers (aged 6 months to 18 years) who are on long-term aspirin therapy and therefore could develop Reye Syndrome after the flu; and
- women who will be more than 3 months pregnant during the flu season.

Who Should Not Get a Flu Shot? The following groups should not get a flu shot before talking with their doctor:
- People who are have a severe allergy to hens` eggs
- People who have had a severe reaction to a flu shot in the past
- People who previously developed Guillain-Barré syndrome (GBS) in the 6 weeks after getting a flu shot

Who should get a flu shot? People at high risk for complications of the flu and people in close contact with them (including household members) should get the vaccine.
Talk with a doctor before getting a flu shot if you:
1) Have ever had a severe allergic reaction to eggs or to a previous flu shot or
2) Have a history of Guillain-Barré Syndrome (GBS).

If you are sick with a fever when you go to get your flu shot, you should talk to your doctor or nurse about getting your shot at a later date. However, you can get a flu shot at the same time you have a respiratory illness without fever or if you have another mild illness.

Why do I need to get a flu shot every year? Flu viruses change from year to year, which means two things. First, you can get the flu more than once during your lifetime. The immunity (natural protection that develops against a disease after a person has had that disease) that is built up from having the flu caused by one virus strain doesn`t always hold up when a new strain is circulating. Second, a vaccine made against one flu virus may not protect against the newer viruses. That is why the influenza vaccine is updated to include current viruses every year.

A third reason to get a flu vaccine every year is that after you get a flu shot, your immunity to the flu declines over time and may be too low to provide protection after one year.

Does a flu shot work right away? No. It takes about two weeks after the vaccination for antibodies to develop in the body and provide protection against influenza virus infection. In the meantime, you are still at risk for getting the flu. That`s why it`s better to get vaccinated early in the fall, before the flu season really gets under way.

Can I get the flu even though I got a flu shot this year? Yes. The ability of a flu shot to protect a person depends on two things: 1) the age and health status of the person getting the shot, and 2) the similarity or "match" between the virus strains in the vaccine and those in circulation. When the "match" between vaccine and circulating strains is close, flu vaccine prevents influenza in about 70 to 90 percent of healthy persons younger than age 65 years. Among elderly persons living outside chronic-care facilities (such as nursing homes) and those persons with long-term (chronic) medical conditions, flu vaccine is 30%-70% effective in preventing hospitalization for pneumonia and influenza. Among elderly nursing home residents, flu vaccine is most effective in preventing severe illness, secondary complications, and deaths related to the flu. In this population, the vaccine can be 50%-60% effective in preventing hospitalization or pneumonia and 80% effective in preventing death from the flu.

Many people think that "the flu" is any illness with fever or cold-like symptoms, or any illness with stomach or intestinal problems, such as vomiting, nausea, or diarrhea. They may expect flu vaccine to prevent these illnesses. But flu shots are effective only against illness caused by flu viruses, and not against other causes of fever, colds, or gastro-intestinal illnesses caused by other viruses.

How are the viruses for flu shots selected? Each year, many labs throughout the world, including in the United States, collect flu viruses. Some of these flu viruses are sent to one of four World Health Organization (WHO) reference labs, one of which is at the Centers for Disease Control and Prevention (CDC) in Atlanta, for detailed testing. These laboratories also test how well antibodies made to the current vaccine react to the circulating virus and new flu viruses. This information, along with information about flu activity, is summarized and presented to an advisory committee of the U.S. Food and Drug Administration (FDA) and at a WHO meeting. These meetings result in the selection of three viruses (two subtypes of influenza A viruses and one influenza B virus) to go into flu shots for the following fall and winter. Usually one or two of the three virus strains change in the vaccine each year.

What are the risks from getting a flu shot? The viruses in the flu shot are killed (inactivated), so you cannot get the flu from a flu shot. The risk of a flu shot causing serious harm, or death, is extremely small. However, a vaccine, like any medicine, may rarely cause serious problems, such as severe allergic reactions. Almost all people who get influenza vaccine have no serious problems from it.

What are the side effects that could occur? - Soreness, redness, or swelling where the shot was given
- Fever (low grade)
- Aches
If these problems occur, they begin soon after the shot and usually last one to two days.

Can severe problems occur? Life-threatening allergic reactions are very rare. Signs of serious allergic reaction can include breathing problems, hoarseness or wheezing, hives, paleness, weakness, a fast heartbeat, or dizziness. If they do occur, it is within a few minutes to a few hours after the shot. These reactions are more likely to occur among persons with a severe allergy to eggs, because the viruses used in the influenza vaccine are grown in hens` eggs. People who have had a severe reaction to eggs or to a flu shot in the past should not get a flu shot before seeing a physician.

What should I do if I have had a serious reaction to influenza vaccine? Call a doctor, or get to a doctor right away. Tell your doctor what happened, the date and time it happened, and when you got the flu shot.