The Spread of Yellow Fever

The Spread of Yellow Fever
Yellow fever is a dangerous disease that is primarily found in tropical climates. Sometimes, people infected with yellow fever suffer only mild flu-like symptoms. In other cases, however, yellow fever can be much more serious, causing kidney problems, liver failure, and sometimes, even death. For many years, people believed that the disease was spread from person to person, much like the cold or flu. However, this was not the case. It took the dedicated research of a doctor named Carlos Juan Finlay to show people how to prevent a disease that was killing people by the thousands.
In the 1800's, yellow fever was a serious threat to Cuba's population. Because people believed that the disease was spread from person to person, they tried to prevent the spread of the disease by quarantining people. However, this did not help.
Dr) Finlay had a different hypothesis. He noticed the worst outbreaks of yellow fever happened when mosquitoes were most active. This led him to theorize that mosquitoes spread the disease, not people. This was a revolutionary idea; no one had considered the possibility of mosquitoes being vectors of disease. In fact, the idea was so revolutionary that no one believed Finlay for over 20 years.
Eventually, Finlay's theory was proven. A team of military doctors led by Dr. Walter Reed conducted a series of experiments that proved once and for all that mosquitoes were indeed responsible for spreading yellow fever. Armed with this information, people took new measures to protect themselves from yellow fever. As a result of this discovery, yellow fever has almost completely disappeared from Cuba and many other nations.
According to the text, which of the following is true regarding mosquitoes?

A) There is a large number of mosquitoes in Cuba.
B) When mosquitoes were most active, the worst cases of yellow fever occurred.
C) After mosquitoes bit a person, yellow fever was spread from person to person.
D) As a result of the study, mosquitoes are currently inactive.