It is clear from the passage that ....... .

Humans, because of the diversity of their genetic makeup, react to epidemic diseases in different
ways. Some people have" acquired immunity for a different disease, others have partial immunity,
and still others have no immunity. It is possible to have an immunity for one disease while being
susceptible to others. Sometimes an immunity can he temporary, as in the case of influenza. Some
diseases, such as measles, confer permanent immunity on those who have had them. A few diseases,
including chicken pox and rheumatic fever, can infect an individual early in life and then lie
dormant for many years before becoming active again in another way.