Seasonal flu typically hits the elderly hardest (with 80 % of total deaths seen in those over the age of 65), but H1N1 on the other hand, can result in overstimulation of a young person's immune system in response to the virus, which can damage the lungs and kidneys and even potentially cause organ failure and death.
不同的是，一般流感多侵襲老人（80 % 死亡者為 65 歲以上老人），但 H1N1 病毒卻可能造成免疫力較強的青壯族出現「免疫風暴」，也就是說，免疫系統為了攻擊入侵的新病毒，在殺死病毒的同時也出現激烈的免疫反應，損傷了肺臟、腎臟，甚至因器官衰竭而死亡。