What is Seasonal Influenza (flu)?
Seasonal influenza is commonly referred to as “the flu.” It is a contagious respiratory illness caused by influenza viruses. Flu can cause mild to severe illness, and at times can lead to death. Flu viruses can be detected year-round in the United States, but they are most common during the fall and winter.
There are two types of flu viruses that cause human seasonal illness: Types A and B. Type A has many different subtypes based on proteins on the surface of the virus that tend to change from year to year. Type B viruses generally change more slowly compared to type A influenza viruses.
Who gets flu?
Anyone can get flu and develop serious illness. However, some people are at higher risk of developing serious flu-related complications if they get sick. This includes young children (under the age of five years, but especially those younger than two years, pregnant women, people aged 65 years and older, and people with chronic illnesses (e.g., lung disease, heart disease, cancer, or diabetes) or weakened immune systems.
How is flu spread?
People spread flu to others by coughing, sneezing, or talking, which creates small respiratory droplets that contain the virus. Less often, a person might get flu by touching a surface or object that has the flu virus on it and then touching his or her mouth, nose, or eyes.
People with flu are most contagious in the first three to four days of their illness. Some people can start spreading the virus beginning one day before symptoms develop and up to five to seven days after becoming sick. Young children and some people with weakened immune systems, may be contagious for longer periods of time.
What are the symptoms of flu?
Flu symptoms usually come on suddenly. Symptoms can include fever or feeling feverish/chills, cough, sore throat, runny or stuffy nose, headache, fatigue, and muscle or body aches. Some people may have vomiting and diarrhea, but this is more common in children. Most people with flu recover within a few days to less than two weeks. However, some people might develop severe or life-threatening complications, like pneumonia.
How soon after exposure do symptoms appear?
The time from when a person is exposed and infected with flu to when symptoms begin is about two days but can range from about one to four days.
How is flu diagnosed?
Healthcare providers usually diagnose flu based on symptoms. It is difficult to distinguish flu from other viral or bacterial respiratory illnesses based on symptoms alone. There are multiple tests that can detect flu viruses. There are rapid tests that can provide results within 10–20 minutes. There are several more accurate flu tests that must be performed in specialized laboratories. These tests require a healthcare provider swipe the inside of your nose or the back of your throat with a swab and then send the swab for testing.
What is the treatment for flu?
Rest, liquids, and over-the-counter medicines for fever and discomfort are the usual treatments. Prescription antiviral medications are available to people who are very sick with flu or at increased risk of developing serious flu complications. These treatments can reduce the severity of flu and shorten the time someone is sick. They work best when started within one to two days after symptoms begin. Check with your doctor promptly about treatment if you have flu symptoms and are at higher risk of serious flu complications. Aspirin should not be given to children younger than 19 years old with fever-causing illnesses like flu because of the possibility of a rare but serious illness called Reye’s syndrome. Antibiotics are not used to treat flu.
Do people who have been in contact with someone with flu infection need to be tested and treated?
Close contacts of a person with flu might want to contact their healthcare provider or seek medical evaluation for vaccination, testing, or antiviral medication to prevent flu.
In the setting of a flu outbreak, testing and treatment may also be recommended, particularly if the outbreak occurs in a healthcare setting.
How can flu be prevented?
There are actions to help protect yourself and are sick. If you are sick, limit contact with others as much as possible.
- Getting a flu vaccine every year is the most important action you can take to prevent the flu.
- Stay home if you are sick to prevent spreading the virus to others. You can return to normal activities when, after 24 hours, the following are both true:
- Your symptoms have improved overall, AND
- You have no fever (without the use of fever-reducing medication).
- Take steps for cleaner air. This can include opening a window to let in fresh air and maintaining central heating, ventilation, and air conditioning (HVAC) systems.
- Practice good hygiene.
- Cover coughs and sneezes.
- Wash hands often with soap and water for at least 20 seconds. If water is unavailable, use an alcohol-based hand sanitizer containing at least 60% alcohol.
- Clean and disinfect frequently touched surfaces
- Take flu antiviral drugs if your doctor prescribes them.
Who should be vaccinated against flu?
Everyone aged six months or older, with rare exceptions, should get a flu vaccine each year. Vaccination is especially important for people who are at higher risk of developing serious flu complications. Talk to a healthcare provider if you have questions about flu vaccines.
If I was vaccinated for flu last year, do I need to get vaccinated this year?
Yes. It is important to get vaccinated for flu every year. The flu vaccine formulation changes year to year to best match the flu viruses research indicates will be most common during the upcoming season. Also, protection from the flu vaccine decreases over time, so getting a flu vaccine every year will give you the best protection.
How can I get more information about flu?
- If you have concerns about flu, contact a healthcare provider.
- Contact your local health department.
- Visit the VDH Influenza (Flu) in Virginia page or CDC Flu page.
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