Viruses can shape human history, as did the yellow fever virus. It shaped the development of America. In 1800, Thomas Jefferson stated that "yellow fever will discourage the growth of great cities in our nation."

This fear drove the need for basic public health services such as clean water supply, sewage systems, and a health department.

Epidemics in Barbados in 1647, Yucatan and Cuba in 1648 signaled the establishment of this disease in the Western Hemisphere. Since the black slaves in the Caribbean are immune to the disease, it suggests that it originally came from Africa.

Previously unexposed people had a 50% chance of survival.

It struck Charleston and Philadelphia for the first time in 1699. New York lost 10% of it's population in 1702. In 1793, Philadelphia lost 15% of it's population when over 4,000 died between August and October. Those who didn't die tried to flee the city. Society was ripped apart. Family members abandoned each other. Natives blamed foreigners, which were Germans and Haitian immigrants this time. Clerics found reason not to assist the helpless, and a provisional government was established ot maintain some city services in the absence of office holders. It was much like it was during the Black Plague. It was also one reason Philadelphia became less of a shipping/trading port than New York.

In 1802, Nepoleon tried to defeat a slave revolt in Haiti. Unfortunately his troops met up with the yellow fever which killed 22,000 of his 25,000 troops. It made him decide to sell the Louisiana Territory to the U.S. in 1803 thus doubling the size of the U.S. overnight. Haiti also declared independence soon after in 1804 to become the first black nation to be free from European colonial rule.

The mosquito was first identified as a carrier in 1881 and later proved to be so by Dr. Walter Reed's Yellow Fever Commission and from recent proof that mosquitoes caused malaria. in 1902. However, many people have guessed at this. A Cuban physician named Doctor Carlos Finlay guessed it was Aedes in 1818.

A vaccine was developed in 1937 and was first given out on a mass basis in French West Africa in 1939. An epidemic in Ethiopia in 1960-2 infected over 100,000 and killed 1/3 of those infected.

The mortality rate for yellow fever can be as high as 10% in large outbreaks but is usually less. It currently occurs in underdeveloped rural areas with lax control measures and /or immunization. In south America there is over 10,000 deaths a year. There was also an outbreak in Kenya in 1993.