Q- Why a person suffering from smallpox cannot suffer from that disease again?
Answer- We all knows that smallpox is a kind of infectious disease that is mainly caused due to two major virus variants. Now according to the question, it is absolutely right that any person who is suffering from or has recently suffered from smallpox cannot suffer from that same disease again because once our body recover from any disease so it stores the data of structure of DNA of that microbe or virus of disease so that if that virus or microbe again enters in our body so body creates started creating WBCs (Antibodies: that help in defense against that microbe or virus) with the help of that same DNA structure to defeat those microbes. So that virus of the same disease cannot survive in body of a particular person anymore. This is the reason behind any person who is suffering or has suffered from smallpox cannot suffer from it again.
By the way the agent that causes smallpox are as follows:
1. Variola Minor
2. Variola Major
These both agents of smallpox disease belong to Genus Orthopoxvirus.