@greg_travis @TRyanGregory It presents with a wide range of severity from asymptomatic to death. You probably don't remember the milder cases, may not have even known about them.
Moderate or worse flu is likely much less than 1/5 years.
@greg_travis @TRyanGregory 它呈现出从无症状到死亡的各种严重程度。您可能不记得较轻的病例，甚至可能不知道它们。
中度或更严重的流感可能远少于 1/5 年。