What is yellow fever? Yellow fever is a disease caused by a virus that is spread to humans by the bite of an infected mosquito.

Yellow fever is an acute viral infectious disease that is transmitted to humans through the bite of infected mosquitoes.

yellow fever can also be a life-threatening disease causing hemorrhagic fever andhepatitis (hence the term "yellow" from the jaundice it can cause).

This viral disease occurs in tropical areas of Africa and South America, and each year there are an estimated 200,000 cases of yellow fever worldwide, leading to approximately 30,000 deaths. An increase in the number of cases of yellow fever in the last few decades has led to campaigns aimed at improving public awareness and disease prevention for this re-emerging infectious disease.

Yellow fever is a disease caused a virus, which is spread through mosquito bites. Symptoms take 3–6 days to develop and include fever, chills, headache, backache, and muscle aches. About 15% of people who get yellow fever develop serious illness that can lead to bleeding, shock, organ failure, and sometimes death.

Travelers to certain parts of South America  and Africa  are at risk for yellow fever.

What can travelers do to prevent yellow fever?

Vectorborne transmission occurs via the bite of an infected mosquito, primarily Aedes or Haemagogus spp. Nonhuman and human primates are the main reservoirs of the virus, with anthroponotic (human-to-vector-to-human) transmission occurring. There are 3 transmission cycles for yellow fever: sylvatic (jungle), intermediate (savannah), and urban.

RISK FOR TRAVELERSA traveler’s risk for acquiring yellow fever is determined by various factors, including immunization status, location of travel, season, duration of exposure, occupational and recreational activities while traveling, and local rate of virus transmission at the time of travel

Yellow fever occurs in sub-Saharan Africa and tropical South America, where it is endemic and intermittently epidemic

In the summer of 1793 Philadelphia was unusually hot, and dry, and congested. By June, a thousand refugees fleeing from revolution on the island of Santo Domingo had poured into the city. Their tales of slave revolt and of a fever epidemic engendered some support, and $15,000 dollars in relief money was quickly raised.

In August of 1793, several prominent Philadelphia physicians gathered to discuss a worrying trend: an increasing number of patients with symptoms of nausea, black vomit, lethargy, and yellow skin coloration. Among those present was Dr. Benjamin Rush, the city's most prominent doctor, signer of the Declaration of Independence, and supporter of the state and national constitutions. He quickly concluded that the culprit was the dreaded yellow fever.

After the bite of the infecting mosquito, there is an incubation period of several days while the virus multiplies within the body. The onset of symptoms is then abrupt, with headache, backache, rapidly rising fever, nausea, and vomiting. Jaundice (yellowing of the skin and eyes) is a common sign in persons and gives rise to the name yellow fever. This acute stage lasts two or three days, after which the patient either begins to recover or gets worse. Death may occur six or seven days after the onset of symptoms.

The yellow fever patient’s recovery is long, but, when it does occur, it is complete and is accompanied by a lifelong immunity.

Many persons may experience only a mild infection that lasts a few days.

It was the summer of 1793 and a ghastly epidemic of Yellow fever gripped the largest city of America and the nation’s capital. Samuel Breck, a newly arrived merchant to Philadelphia and later instructor to the blind, observed “the horrors of this memorable affliction were extensive and heart rending.” Samuel Breck estimated that the number of deaths in 1793 by yellow fever was more than four thousand. Modern scholars estimate the number to be closer to five thousand, a tenth of the capital’s fifty thousand residents. However, twenty thousand people, including Thomas Jefferson, George Washington, and much of the federal government had fled the city to escape the fever thereby making proportion of deaths among those who remained quite high. What could cause such a devastating epidemic to occur on Pennsylvania soil?

Yellow fever is an acute, infectious, hemorrhagic (bleeding) viral disease transmitted by the bite of a female mosquito native to tropical and subtropical regions of South America and Africa. However, it wasn’t discovered that Yellow Fever was transmitted by mosquitoes until 1881. At the time, Yellow Fever was a well known illness that affected sailors who travelled to the Caribbean and Africa characterized by disquieting color changes including yellow eyes and skin, purple blotches under the skin from internal bleeding and hemorrhages, and black stools and vomit, all of which were accompanied by a high fever.

In 1793, people of the French Caribbean colony of Saint Domingue (now Haiti) were fleeing a revolution from France and thousands of infected individuals landed at the Philadelphia docks. This combined with the dry, hot summer and low water tables of 1793 created the perfect breeding grounds for mosquitoes and the spread of Yellow Fever.