Influenza (the flu) is a contagious disease that is caused by 3 viruses, influenza A, B and C. It attacks the respiratory tract (nose, throat, and lungs). Type A is usually responsible for the large outbreaks and is a constantly changing virus. New strains of Type A develop regularly and cause new epidemics every few years. Type B causes smaller outbreaks, and Type C usually causes mild illness. The flu is different from a cold. While both are caused by viruses, high fever, headaches and extreme exhaustion are much more common with the flu. The flu can also cause serious complications such as bronchitis and pneumonia for certain high-risk groups.
Millions of people in the U.S. - about 10% to 20% of the population - will get the flu each year. Most people who get the flu will recover in 1 to 2 weeks, but some people will develop life-threatening complications (such as pneumonia) as a result of the flu. An average of about 20,000 people per year in the U.S. die from the flu, and 114,000 per year have to be admitted to the hospital as a result of influenza.
The flu is transmitted when a person who has the flu coughs, sneezes, or speaks and sends the flu virus into the air, and other people inhale the virus. The virus enters the nose, throat, or lungs and begins to multiply, causing flu symptoms. Less often, the flu may be spread when a person touches a surface that has flu viruses on it, such as a doorknob, and then touches their nose or mouth.
The flu usually comes on suddenly and may include these symptoms:
- Tiredness (can be extreme)
- Dry cough
- Sore throat
- Nasal congestion
- Body aches
- Loss of appetite
These symptoms are usually referred to as "flu-like symptoms." In addition to the flu virus, several other respiratory viruses also can circulate during the flu season and can cause symptoms and illness similar to those seen with flu infection. These non-flu viruses include rhinovirus (one cause of the common cold) and respiratory syncytial virus (RSV).
People of any age with chronic medical conditions, people over 65 years old and very young children are more likely to get complications from the flu. Pneumonia, bronchitis, and sinus and ear infections are three examples of complications from the 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.
A person can spread the flu starting 1 day before they feel sick. Adults can continue to pass the flu virus to others for another 3 to 7 days after symptoms start. Children can pass the virus for longer than 7 days. Symptoms start 1 to 4 days after the virus enters the body. Some people can be infected with the flu virus but have no symptoms. During this time, those people can still spread the virus to others.
It is very difficult to distinguish the flu from other viral or bacterial causes of respiratory illnesses on the basis of symptoms alone. A test can confirm that an illness is influenza if the patient is tested within the first 2 to 3 days after symptoms begin. In addition, a medical provider's exam may be needed to determine whether a person has another infection that is a complication of the flu.
For mild flu in people who are not high risk (people who do not have chronic medical conditions, HIV, asthma or anemia), the following is the most common treatment:
- Drink plenty of liquids
- Avoid using alcohol and tobacco
- Take pain medication (such as Advil or Tylenol) to relieve the symptoms of flu. Do NOT take aspirin because it can cause Reye syndrome, a rare but serious illness in teenagers and children.
Influenza is caused by a virus, so antibiotics don't work to cure it. The best way to prevent the flu is to get an influenza vaccine (flu shot) each fall, before flu season.
If the flu is diagnosed within 48 hours of the onset of symptoms, several antiviral medications are available for people in high-risk groups. These medications may shorten the duration of symptoms by approximately 1 day. They must be prescribed by a medical provider and may have side effects.
Many people use the term "stomach flu" to describe illnesses with nausea, vomiting, or diarrhea that are not caused by the flu virus, but can be caused by many different viruses, bacteria, or even parasites. However, while vomiting, diarrhea, and being "sick to your stomach" can sometimes be related to the flu - particularly in children - these problems are rarely the main symptoms of influenza. The flu is a respiratory disease and not a stomach or intestinal disease. Learn more about the stomach flu (viral gastroenteritis) here.
In the U.S., the peak of flu season can occur anywhere from late December through March.
Anyone can get the flu (even healthy people), and serious problems from flu can happen at any age. We usually recommend that college students get a flu shot because it is easily spread in residence halls and other typical college settings. Other groups that should usually be vaccinated include:
• Pregnant women
• People with significant asthma or other respiratory illness
• People with significant chronic cardiovascular, liver, blood, neurologic disease
• Those who have diabetes, HIV, or are taking immunosuppressive drugs
The following groups should not get a flu shot before talking with their doctor:
- People who are have a severe allergy to eggs or thimerosal (a medication preservative)
- People who have had a severe reaction to a flu shot in the past
- People who previously developed Guillain-Barre syndrome (a disease which causes nerve damage) in the 6 weeks after getting a flu shot
- If you are sick, have an acute respiratory infection or have a fever, you should delay getting the flu shot until your symptoms are gone
Every fall, Health Services provides free flu shots for all Brown students. We will advertise this across campus as soon as the flu shots become available. If you have any questions, you can call Nursing at 401.863-1330.The vaccine provides protection against seasonal flu and H1N1.
Centers for Disease Control
The majority of the information on this page is taken from this site.
This site has several articles on influenza, including the latest news, general overviews and diagrams.
Disclaimer: Health Education is part of Health Services at Brown University. Health Education maintains this site as a resource for Brown students. This site is not intended to replace consultation with your medical providers. No site can replace real conversation. Health Education offers no endorsement of and assumes no liability for the currency, accuracy, or availability of the information on the sites we link to or the care provided by the resources listed. Health Services staff are available to treat and give medical advice to Brown University students only. If you are not a Brown student, but are in need of medical assistance please call your own health care provider or in case of an emergency, dial 911. Please contact us if you have comments, questions or suggestions.