The first reason is their size. They are very small and are very difficult to see. Special technology needed to be developed in order to observe them and their behavior and reach the conclusion that they were in fact infectious agents that could cause diseases. This wasn't possible before because the microscopes weren't as well developed.
Another is that they have a very long incubation period. This means that if you have them, a long time will pass before they start harming you which meant that many people believed them to be harmless since they couldn't track their behavior over a longer time period, also due to the lack of good technology.
Answer:
There were many motives for overseas imperialism by the United States in the late nineteenth century. Let us look at a few of them.
The desire for overseas markets: Many American economists feared the effects of "overproduction." They thought that the domestic market was not big enough to sustain continued industrial growth. So they advocated different methods to secure overseas markets. This was especially important in China, where Secretary of State John Hay.
Explanation:
I believe it is the last option... "Its political system cannot be easily changed.
An eight hour day, an end to child labor and work
