Yellow Fever- Its Five Phases and Its History in America

Yellow fever is an extremely infectious disease that is brought on by a virus. Yellow fever has been responsible over the years for many serious epidemics that have killed thousands upon thousands of people. Yellow fever is passed from monkeys to humans through the bite of infected mosquitoes, and is prevalent in Africa and South America, where it still kills an estimated 30,000 people annually despite the fact that there is a vaccination that can prevent it.

Direct transmission from person to person is not possible with yellow fever; people get it when a mosquito bites a monkey that is infected with the disease and then passes it on to humans when they bite them. This cycle continues, as mosquitoes infect both humans and monkeys with yellow fever. A minute virus known as a flavivirus is responsible for yellow fever, and once it has been injected into a person's system, the chances of them coming down with the malady range from five to twenty percent. The immune system of the individual may destroy the virus, or the effects of it can be so mild that yellow fever is never even suspected.

There are five very marked stages to a case of yellow fever in a human being. The first, incubation, takes three to six days, during which time none of the condition's symptoms manifest themselves. The second stage, invasion, lasts two to three days and brings with it fever and chills, intense pounding headaches and backaches, muscle pain, nausea, and overall fatigue. A person with yellow fever in the invasion stage will have a white coating in the center of their tongue with a swollen red border. Most fevers bring a higher heart rate, but yellow fever causes the heart to actually slow down, a condition known as Faget's sign. During the invasion stage of yellow fever, the virus is still active and alive in the person and can be passed to others through mosquito bites.