Yellow fever: Symptoms, causes, and prevention

Yellow fever is a hemorrhagic condition that can lead to a high fever, bleeding into the skin, and cell death in the liver and kidneys. If enough liver cells die, liver damage occurs, leading to jaundice, a condition in which the skin takes on a yellowish color.

It is an acute, systemic disease, meaning that it starts suddenly, and it affects the whole body. The Flavivirus causes yellow fever.

The virus is transmitted by mosquitos, mainly the Aedes and Haemogogus species.

It is most likely to occur in tropical and subtropical parts of South America, parts of the Caribbean, and
Africa. It rarely affects American travelers.

The World Health Organization (WHO) estimate that in 2013, there were between 84,000 severe cases of yellow fever and between 29,000 and 60,000 fatalities. About 90 percent of all cases occur in Africa.

An outbreak is currently underway in Brazil, and the Centers for Disease Control and Prevention (CDC) has in place a level 2 alert for travelers.

Fast facts on yellow fever

Here are some key points about cold yellow fever. More detail and supporting information is in the main article.

Yellow fever is transmitted by mosquitoes.

It can cause a high fever and organ damage, and it can be fatal.

There is no specific treatment, so people will receive supportive care.

Travelers to affected areas should check if they need a vaccine before they travel.

Some countries will not allow a traveler to enter without an immunization certificate.


[Yellow fever mosquito]
Yellow fever is spread by mosquitos.

Mosquitoes spread yellow fever. It can affect monkeys and humans.

If a mosquito bites a monkey that has the fever, they can pass it to humans. This can lead to outbreaks.

After having it once, a person is generally immune, meaning that they are unlikely to have it again.

Yellow fever can occur in settlements close to the jungle, where infected monkeys and mosquitoes live, and it can spread from there.

[Jaundice is a sign of yellow fever]
Yellow fever gets its name from the symptoms of jaundice.

recurring fever

abdominal pain

vomiting, sometimes with blood

tiredness, sluggishness, lethargy

jaundice, which gives the skin and whites of the eyes a yellow tinge

kidney failure

liver failure


delirium, seizures, and sometimes coma

arrhythmias, or irregular heartbeats

bleeding from the nose, mouth, and eyes

Between 20 percent and 50 percent of people who develop toxic stage symptoms die within two weeks.

Within 7 to 10 days, yellow fever is fatal in around half of all people who enter the toxic phase.

Those who recover do not generally have any organ damage and are immune for life.

Causes and risk factors

A flavivirus causes yellow fever.

It is transmitted by mosquito bite, usually the Aedes aegypti mosquito. The mosquito becomes
infected by biting an infected human or a monkey. An infected mosquito is a source of infection for the rest of its life.

[Yellow fever monkey]
Mosquitos can pick up yellow fever from the monkeys that inhabit the jungle canopy, or from infected humans.

Apart from mosquitoes, the only other known hosts of the virus are primates and humans.

The flavivirus is believed to be endemic among monkeys that live in the tree tops of the jungle, known as the jungle canopy, in many parts of Africa and the Americas.

If the infected mosquito passes the flavivirus on to a person who is in the jungle, that person may become a source of infection when they return to their community. They can go on to infect other people.

Anybody who travels to an area where the yellow fever virus is present is at risk of becoming infected.

These areas include parts of Africa, especially sub-Saharan Africa, tropical South America, and some parts of the Caribbean.

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