What age groups are most likely to be affected by avian influenza or another pandemic influenza?

Dr. Anthony Fauci

Director, National Institute of Allergy & Infectious Disease 

Historically, in the 1918 pandemic flu, paradoxically, young healthy individuals were more severely afflicted, and that was felt likely to be due to the fact that they mounted a very vigorous immune response and inflammatory response to the virus, and that, in and of itself, damaged their lungs and created more severe disease.  It's really impossible, when you have a new virus and you don't know what its pattern of disease is, to say which age group is going to be more susceptible to complications.  For sure, traditionally, you know the very old and the very young tend to have the more complications.  Whether or not the young, healthy group would have it with a new pandemic like it was in 1918, that just remains to be seen.  Well hopefully, we'll never see that because we'll never get the pandemic.