Flu: General Information

Synonyms and Related Terms

Synonyms of Flu:

  • flu
  • influenza with non-respiratory manifestation
  • Influenza with non-respiratory manifestation (disorder)
  • Influenza with other manifestations
  • Influenza with other manifestations (disorder)
  • Influenza with other manifestations NOS (disorder)
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Categories

Category of Flu:

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Categories

Categories for Flu may include:5 Category of Flu:

Prevalence of Flu

As many as 1 in 5 Americans come down with the flu each year, and kids are 2 to 3 times more likely than adults to get sick with the flu.

Source: NIH News in Health (NIH)6

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Each year, 5% to 20%of U.S. residents acquire an influenza virus infection, and many will seek medical care in ambulatory healthcare settings (e.g., pediatricians’ offices, urgent-care clinics). In addition, more than 200,000 persons, on average, are hospitalized each year.

Source: CDC7

Contagiousness of Flu

Flu is highly contagious. When infected people cough or sneeze, the flu virus can spread to others up to 6 feet away.

Source: NIH News in Health (NIH)8

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When you’re sick, each cough or sneeze can propel droplets laden with microbes into the surrounding air. These droplets can travel as far as 3 feet. Anyone in their path may be at risk for infection. That’s why covering your mouth and nose—with a tissue, the crook of your elbow or even your hand—is the considerate thing to do.

Microbes can survive outside the body, too. Some can live for 2 hours or more on doorknobs, faucets, keyboards and other surfaces. If you touch a germ-covered surface and then touch your eyes, nose or mouth, you increase your chance of getting infected and getting sick.

Source: NIH News in Health (NIH)9

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Influenza, or flu, is a contagious respiratory infection caused by several flu viruses that infect the nose, throat and lungs.

Source: NIAID (NIH)10

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TRANSMISSION

Influenza viruses spread from person to person, primarily through respiratory droplet transmission (such as when an infected person coughs or sneezes near a susceptible person). Transmission via large-particle droplets requires close contact between the source and the recipient, because droplets generally travel only short distances (approximately 6 feet or less) through the air, before settling onto surfaces. Airborne transmission via small-particle aerosols in the vicinity of the infectious person may also occur. Indirect transmission can also occur when a person touches a virus-contaminated surface and then touches his or her face. However, the relative contribution of the different modes of transmission to the spread of influenza viruses is unclear.

Most adults who are ill with influenza shed the virus in the upper respiratory tract and are infectious from the day before symptom onset to approximately 5-7 days after symptom onset. Ninety-five percent of virus transmission occurs within 3 days after illness onset. Children and those who are immunocompromised or severely ill, including those who are hospitalized, may shed influenza virus for 10 days or more after the onset of symptoms. Seasonal influenza viruses have rarely been detected from nonrespiratory sources such as stool or blood.

Source: CDC Yellow Book 201611

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Flu is usually spread through infected people coughing and sneezing, which temporarily contaminates the surrounding air and surfaces with infected droplets. You can reduce the risk of infection by getting vaccinated and practising good hand and respiratory hygiene.

Source: Queensland Health12

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Transmission

The flu can spread from person to person by:

  • droplets spread from an infected person's coughs or sneezes (these droplets generally travel less than 1 metre)
  • touching surfaces contaminated by infected droplets (including hands, phones, keyboards and door handles) and then touching your mouth, nose, or eyes.

People with flu can be infectious to others from 24 hours before symptoms start until a week after the start of symptoms. Even people with mild flu illness can transmit the infection.

Source: Queensland Health13

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Flu viruses are spread mainly by the droplets made when people with the flu sneeze, cough, or talk. These droplets can land in the mouths or noses of people who are nearby. You might also become infected by touching a surface or object that is contaminated with the flu virus and then touching your own mouth, eyes, or nose.

Source: MedLinePlus Magazine (NIH)14

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How flu spreads

Most experts believe that flu viruses spread mainly by droplets made when people with flu cough, sneeze, or talk. These droplets can land in the mouths or noses of people who are nearby. Less often, a person might also get flu by touching a surface or object that has flu virus on it and then touching their own mouth, eyes, or possibly their nose.

Source: MedLinePlus Magazine (NIH)15

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Period of contagiousness

You may be able to pass on the flu to someone else before you know you are sick, as well as while you are sick. Most healthy adults may be able to infect others beginning one day before symptoms develop and up to 5 to 7 days after becoming sick. Some people, especially young children and people with weakened immune systems, might be able to infect others for an even longer time.

Source: MedLinePlus Magazine (NIH)16

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The flu spreads quickly from person to person through touch and through the air.

While you’re unwell, stay away from work or school. Look after yourself and your family - rest and fluids are especially important.

Source: New Zealand Health17

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Cases are infectious 1 day before to 3 to 5 days after symptoms appear.

Source: GOV.UK18

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Spread

By breathing in droplets coughed out into the air by infected people or by the droplets landing on mucous membranes. Transmission may also occur by direct or indirect contact with respiratory secretions for example via soiled tissues, surfaces.

Source: GOV.UK19

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Exclusion

There is no precise exclusion period. Adults and children with symptoms of influenza are advised to remain at home until recovered.

Source: GOV.UK20

Race/Ethnicity and Flu

Compared to the general U.S. population, American Indians and Alaska Natives are more likely to be hospitalized from the flu than the general U.S. population. Experts aren't sure exactly why, but reasons that these populations are at high risk of flu complications could include social and economic factors that often result in reduced access to health care and crowded living conditions.

Source: CDC Features21

Seasonality of Flu

Each year, from late fall through winter, the number of cold and flu cases in the U.S. climbs dramatically.

Source: NIH News in Health (NIH)22

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Each winter, millions of people suffer from the fever, aches and pains caused by the flu, a highly contagious infection.

Source: NIH News in Health (NIH)23

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The peak influenza season in the temperate Northern Hemisphere is December through February. In the temperate Southern Hemisphere, the peak influenza season is June through August.

Source: CDC Yellow Book 201624

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The flu can occur all year round but in temperate areas the influenza season typically occurs during the winter months.

Source: Queensland Health25

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The flu season in the United States typically ranges from November through March, but it is never too early to be prepared.

Source: MedLinePlus Magazine (NIH)26

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In temperate climates such as New Zealand’s, you’re more likely to get the flu in winter. Some people get very sick - influenza causes deaths every year.

Source: New Zealand Health27

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It occurs most often in winter in the UK and peaks between January and March.

Source: GOV.UK28

Incubation Period of Flu

The incubation period is usually 1-4 days after exposure.

Source: CDC Yellow Book 201629

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Incubation period is between 1 to 3 days.

Source: GOV.UK30

More Information about Flu

NIH’s National Institute on Aging (NIA) is offering a free fact sheet in Spanish about the flu and how to prevent flu for yourself and your loved ones. Call 1-800-222-2225 weekdays between 8:30 a.m. and 5:00 p.m. Eastern time to order Que Hacer Acerca de la Gripe. A Spanish-speaking information specialist is available to respond to calls. This and other Spanish publications on healthy aging also are available on the NIA website at www.niapublications.org.

Source: NIH News in Health (NIH)31

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Information on the different strains of influenza virus can be found on our health protection archive website.

Seasonal influenza risk assessment for 2015 to 2016, for countries in the EU/EEA can be downloaded from the ECDC website

Source: GOV.UK32

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References

  1. Source: Disease Ontology
  2. ibid.
  3. Source: Monarch Initiative
  4. Source: NCI Thesaurus
  5. Source: MeSH (U.S. National Library of Medicine)
  6. Source: NIH News in Health (NIH): newsinhealth.nih.gov/ issue/ nov2015/ capsule2
  7. Source: CDC: cdc.gov/ HAI/ organisms/ organisms.html
  8. Source: NIH News in Health (NIH): newsinhealth.nih.gov/ issue/ nov2015/ capsule2
  9. Source: NIH News in Health (NIH): newsinhealth.nih.gov/ 2007/ October/ docs/ 01features_02.htm
  10. Source: NIAID (NIH): niaid.nih.gov/ diseases-conditions/ influenza
  11. Source: CDC Yellow Book 2016: cdc.gov/ travel/ yellowbook/ 2016/ infectious-diseases-related-to-travel/ influenza
  12. Source: Queensland Health: conditions.health.qld.gov.au/ HealthCondition/ condition/ 8/ 118/ 82/ influenza-the-flu
  13. ibid.
  14. Source: MedLinePlus Magazine (NIH): medlineplus.gov/ magazine/ issues/ winter16/ articles/ winter16pg12-13.html
  15. Source: MedLinePlus Magazine (NIH): medlineplus.gov/ magazine/ issues/ fall14/ articles/ fall14pg10-11.html
  16. ibid.
  17. Source: New Zealand Health: health.govt.nz/ your-health/ conditions-and-treatments/ diseases-and-illnesses/ influenza
  18. Source: GOV.UK: gov.uk/ government/ publications/ health-protection-in-schools-and-other-childcare-facilities/ chapter-9-managing-specific-infectious-diseases
  19. ibid.
  20. ibid.
  21. Source: CDC Features: cdc.gov/ features/ AIANFlu/ index.html
  22. Source: NIH News in Health (NIH): newsinhealth.nih.gov/ 2007/ October/ docs/ 01features_02.htm
  23. Source: NIH News in Health (NIH): newsinhealth.nih.gov/ 2005/ November2005/ docs/ 02capsules.htm
  24. Source: CDC Yellow Book 2016: cdc.gov/ travel/ yellowbook/ 2016/ the-pre-travel-consultation/ respiratory-infections
  25. Source: Queensland Health: conditions.health.qld.gov.au/ HealthCondition/ condition/ 8/ 118/ 82/ influenza-the-flu
  26. Source: MedLinePlus Magazine (NIH): medlineplus.gov/ magazine/ issues/ fall06/ articles/ fall06pg18-21.html
  27. Source: New Zealand Health: health.govt.nz/ your-health/ conditions-and-treatments/ diseases-and-illnesses/ influenza
  28. Source: GOV.UK: gov.uk/ government/ collections/ seasonal-influenza-guidance-data-and-analysis
  29. Source: CDC Yellow Book 2016: cdc.gov/ travel/ yellowbook/ 2016/ infectious-diseases-related-to-travel/ influenza
  30. Source: GOV.UK: gov.uk/ government/ publications/ health-protection-in-schools-and-other-childcare-facilities/ chapter-9-managing-specific-infectious-diseases
  31. Source: NIH News in Health (NIH): newsinhealth.nih.gov/ 2005/ November2005/ docs/ 02capsules.htm
  32. Source: GOV.UK: gov.uk/ government/ collections/ seasonal-influenza-guidance-data-and-analysis

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Note: This site is for informational purposes only and is not medical advice. See your doctor or other qualified medical professional for all your medical needs.