Flu is a infectious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs. That can reason mild to significant illness, and at times deserve to lead come death. The best method to protect against flu is by obtaining a fluvaccineeach year.

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Flu Symptoms

Influenza (flu) can reason mild to significant illness, and at times can lead come death. Flu is different from a cold. Flu commonly comes on suddenly. People who have actually flu regularly feel some or every one of these symptoms:

fever* or emotion feverish/chillscoughsore throatrunny or stuffy nosemuscle or body achesheadachesfatigue (tiredness)some world may have actually vomiting and also diarrhea, despite this is an ext common in youngsters than adults.

*It’s essential to note that no everyone with flu will have a fever.

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How Flu Spreads

Most experts think that flu viruses spread largely by small droplets make when people with flu cough, sneeze or talk. These droplets deserve to land in the mouths or noses of human being who space nearby. Less often, a person can get flu by touching a surface ar or thing that has actually flu virus top top it and then touching their own mouth, sleep or possibly their eyes.

How Many people Get Sick through Flu Every Year?

A 2018 audioeditorfree.com study published in Clinical contagious Diseasesexternal icon looked in ~ the percent of the U.S. Populace who to be sickened by flu utilizing two various methods and compared the findings. Both approaches had similar findings, which suggested that ~ above average, around 8% the the U.S. Populace gets noble from flu every season, v a selection of in between 3% and 11%, depending upon the season.

Why is the 3% to 11% estimate different from the previously cited 5% come 20% range?

The commonly cited 5% to 20% calculation was based on a study that examined both symptomatic and also asymptomatic influenza illness, which method it likewise looked at people who may have had actually the flu but never knew it due to the fact that they didn’t have any symptoms. The 3% come 11% selection is an calculation of the relationship of people who have symptomatic flu illness.

Who is most most likely to it is in infected through influenza?

The exact same CID studyexternal icon found that kids are most likely to get sick from flu and also that world 65 and older are least likely to gain sick from influenza. Typical incidence worths (or attack rate) by period group were 9.3% for children 0-17 years, 8.8% for adult 18-64 years, and also 3.9% for adults 65 years and also older. This method that kids younger than 18 are more than double as likely to develop a symptomatic flu infection 보다 adults 65 and also older.

How is seasonal incidence that influenza estimated?

Influenza virus infection is so usual that the variety of people infected every season can only be estimated. These statistical estimations space based onaudioeditorfree.com-measured flu hospitalization prices that are adjusted to develop an calculation of the total variety of influenza infections in the United states for a provided flu season.

The approximates for the number of infections are then divided by the census population to calculation the seasonal incidence (or attack rate) of influenza.

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Does seasonal incidence the influenza change based ~ above the severity that flu season?

Yes. The relationship of human being who get sick indigenous flu varies. A paper published in CIDexternal icon uncovered that in between 3% and 11% the the U.S. Populace gets infected and also develops flu symptoms every year. The 3% estimate is from the 2011-2012 season, which was an H1N1-predominant season classified together being of low severity. The estimated incidence of flu condition during two periods was approximately 11%; 2012-2013 was an H3N2-predominant season classified together being of center severity, while 2014-2015 to be an H3N2 primary season classified together being that high severity.

Table 1. Estimates of the Incidence that Symptomatic Influenza by Season and Age-Group, joined States, 2010–2016SeasonPredominant Virus(es)Season SeverityIncidence, %, by age Group0-4 yrs5-17 yrs18-49 yrs50-64 yrs≥65 yrsAll Ages2010-112011-122012-132013-142014-152015-16Median
A/H3N2, A/H1N1pdm09Moderate14.