How is seasonal incidence of influenza estimated? This means that children younger than 18 are more than twice as likely to develop a symptomatic flu infection than adults 65 and older. Median incidence values (or attack rate) by age group were 9.3% for children 0-17 years, 8.8% for adults 18-64 years, and 3.9% for adults 65 years and older. The same CID study external icon found that children are most likely to get sick from flu and that people 65 and older are least likely to get sick from influenza. Who is most likely to be infected with influenza? The 3% to 11% range is an estimate of the proportion of people who have symptomatic flu illness.

The commonly cited 5% to 20% estimate was based on a study that examined both symptomatic and asymptomatic influenza illness, which means it also looked at people who may have had the flu but never knew it because they didn’t have any symptoms. Why is the 3% to 11% estimate different from the previously cited 5% to 20% range? population gets sick from flu each season, with a range of between 3% and 11%, depending on the season. Both methods had similar findings, which suggested that on average, about 8% of the U.S. population who were sickened by flu using two different methods and compared the findings. A 2018 CDC study published in Clinical Infectious Diseases external icon looked at the percentage of the U.S.