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.
Alexander Hamilton and Aaron Burr were both in a political and personal battle
The American colonies chose to declare independence from Great Britain for many reasons. They believed the British were treating the colonists unfairly. The British passed many tax laws that impacted the colonists. The colonists had no representatives in Parliament to vote on or discuss these laws.
Rough Riders
The most famous of all the units fighting in Cuba, the "Rough Riders" was the name given to the First U.S. Volunteer Cavalry under the leadership of Theodore Roosevelt. Roosevelt resigned his position as Assistant Secretary of the Navy in May 1898 to join the volunteer cavalry.
Hope this helps :)