英语语法分析

California is now in the middle of the worst outbreak of pertussis in half a century.

加州目前正处于半个世纪以来最严重的百日咳爆发中。

Caused by the bacterium Bordetella pertussis, it initially resembles a cold with a short dry cough.

致病菌为百日咳博尔德氏杆菌，潜伏期一周，类似普通感冒，伴有短促的干咳。

That can be a sign of pertussis, or whooping cough, which can be serious and has been more prevalent in the past few years.

那可能是百日咳的征兆，这可能很严重并在这几年越来越普遍。