The virus was similar to the 1957-58 Asianflu, so some people may have had some level of immunity.
这种病毒很像1957-58年的“亚洲型流感”病毒，因此许多人已经有了一定的免疫力。
2
Many of the young victims who have become deathly ill turned out to have other medical problems — a phenomenon first clearly seen with the 1957 Asianflu.