- Slideshow: Foods to Eat When You Have the Flu
- Slideshow: Natural Cold & Flu Remedies
- Slideshow: Finding Relief for Your Cough
- Patient Comments: Flu (Influenza) - Symptoms
- Patient Comments: Flu (Influenza) - Side Effects
- Flu (influenza, conventional, H1N1, H3N2, and bird flu [H5N1]) facts
- What is flu (influenza)?
- When does flu season begin and end?
- Flu vs. cold
- What are the causes of the flu (influenza)?
- What are flu (influenza) symptoms in adults and in children?
- What is the incubation period for the flu?
- How long is the flu contagious, and how long does the flu last?
- How is the flu (influenza) diagnosed?
- How does flu spread?
- What is the key to flu (influenza) prevention?
- Are there any flu shot or nasal spray vaccine side effects in adults or in children?
- How effective is the flu vaccine?
- Why should the flu (influenza) vaccine be taken every year?
- What are some flu treatments an individual can do at home (home remedies)?
- What types of doctors treat the flu?
- What can people eat when they have the flu?
- When should a person go to the emergency department for the flu?
- Who should receive the flu vaccine, and who has the highest risk factors? When should someone get the flu shot?
- What is the prognosis for patients who get the flu? What are possible complications of the flu?
- Can the flu be deadly?
- What is the bird (avian) flu?
- Do antiviral agents protect people from the flu?
- What medications treat the flu?
- Is it safe to get a flu shot that contains thimerosal?
- Where can people find additional information about the flu?
Quick GuideFlu Pictures Slideshow: 10 Foods to Eat When You Have the Flu
What is the incubation period for the flu?
Incubation period for the flu, which means the time from exposure to the flu virus until initial symptoms develop, typically is one to four days with an average incubation period of two days.
How long is the flu contagious, and how long does the flu last?
The flu is typically contagious about 24-48 hours before symptoms appear (from about the last day of the incubation period) and in normal healthy adults is contagious for another five to seven days. Children are usually contagious for a little while longer (about seven to 10 days). Individuals with severe infections may be contagious as long as symptoms last (about seven to 14 days). In adults, flu symptoms usually last about five to seven days, but in children, the symptoms may last longer (about seven to 10 days). However, some symptoms such as weakness and fatigue may gradually wane over several weeks.
How is the flu (influenza) diagnosed?
The flu is presumptively diagnosed clinically by the patient's history of association with people known to have the disease and their symptoms listed above. Usually, a quick test (for example, nasopharyngeal swab sample) is done to see if the patient is infected with influenza A or B virus. Most of the tests can distinguish between A and B types. The test can be negative (no flu infection) or positive for types A or B. If it is positive for type A, the person could have a conventional flu strain or a potentially more aggressive strain such as H1N1. Most of the rapid tests are based on PCR technology that identifies the genetic material of the virus. Some rapid influenza diagnostic tests (RIDTs) can screen for influenza in about 10-30 minutes.
Swine flu (H1N1) and other influenza strains like bird flu or H3N2 are definitively diagnosed by identifying the particular surface proteins or genetic material associated with the virus strain. In general, this testing is done in a specialized laboratory. However, doctors' offices are able to send specimens to specialized laboratories if necessary.