They also knew from experiments on pigs, conducted by others, that exposure to one virus during early life has the potential to make infections of other, quite different, viruses later on much more severe than they otherwise would have been. 

分析划线的这个不定式（作the potential的定语）

to make infections of other, quite different, viruses later on much more severe than they otherwise would have been. 

1. 去掉插入成分quite different后：

to make infections of other viruses later on much more severe than they otherwise would have been. 

2. 去掉时间later on后：

to make infections of other viruses much more severe than they otherwise would have been. 

3. 基本结构已经显现：make infections severe （make + 宾语 + adj. 这里形容词作宾补）使感染很严重。变成比较结构后：

4. to make infections of other viruses much more severe than they otherwise would have been. 

5. 全部加进去后：

to make infections of other, quite different, viruses later on much more severe than they otherwise would have been.