Yellow fever

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at February 24, 2016
StartDiseasesYellow fever

Yellow fever occurs primarily in Africa, and there are approximately 200,000 cases of it every year. It is still considered an epidemic in over 40 countries. While it can be a deadly illness, there are measures that can be taken to protect oneself against the disease.


Definition & Facts

Yellow fever is caused by a yellow fever virus and is a viral hemorrhagic fever, like Ebola virus disease. The “hemorrhagic” part refers to hemorrhaging (bleeding); the disease affects several vital organ systems. This can make it even more difficult for the body to heal itself since it is compromised in multiple ways.

The disease is still a major problem in tropical Africa, despite a vaccine being available. The illness is also found in South America, but only about 10% of cases occur there. Since the last epidemic in North America in 1905, it primarily affects only those in North America who travel to affected countries. Worldwide, it still causes approximately 30,000 deaths a year.

Symptoms & Complaints

The disease occurs in two distinct phases, which begin about three to six days after exposure. During the first stage, called the acute phase, common complaints include headache, fever, nausea, vomiting, muscle aches, dizziness, and more flu-like symptoms. Yellow fever can be difficult to diagnose early since these symptoms are common to many illnesses and tropical diseases.

For most people, the symptoms are relatively mild and recovery is reached within several days. About 15% of sufferers, however, move into second stage called the toxic stage. Frequently there may be a day or two in between phases, when the person appears to have recovered. However, then they enter into the second stage, which can include abdominal pain, vomiting (sometimes vomiting blood), liver failure and kidney failure, bradycardia (slow heartbeat), and nosebleeds, bleeding gums, and bleeding eyes.

One of the most prominent symptoms at this stage of yellow fever is the jaundice and yellowed eyes that can occur, for which the disease is named. This is caused by liver dysfunction. The sufferer can also experience brain dysfunction, which can involve a coma, seizures, or delirium. Approximately half of people who reach the second stage die within 10-14 days. Survival rates are often affected by the age and health of the person who contracted the disease.


Yellow fever is caused by an arbovirus which is a term that describes viruses spread by arthropods such as insects. The arboviruses that cause yellow fever belong to the Flavivirus genus which also includes dengue virus, Zika virus, and West Nile virus. It is transmitted primarily by the Aedes aegypti species of mosquito, the same type responsible for transmission of viruses that cause dengue fever and Zika fever.

This mosquito needs very little water to breed, reproduces quickly, and is most active at dawn and dusk—a very common time for people to be out leaving or returning to their homes. This kind of mosquito is efficient at spreading disease, which has led some to discuss the possibility of eradicating the breed.

Yellow fever is not passed on directly from one person to another. It is possible, however, that the disease could be transmitted from needle sticks or blood transfusions that were done with infected blood. There are frequently outbreaks in condensed areas due to the small travel range of the mosquitoes.

An ill person can pass the disease onto non-affected mosquitoes, which then transmit the disease to someone else. For this reason, it is recommended that already sick people try to stay indoors to prevent mosquitoes from feeding on them and then spreading the disease even further. Primates are also susceptible to yellow fever, so the disease can keep circulating even when humans are taking necessary precautions.

Diagnosis & Tests

It can be difficult to make a conclusive diagnosis during the acute phase of yellow fever, as lots of the symptoms are seen in so many other illnesses. A presumptive diagnosis is often made based on symptoms, vaccination status, and the patient’s location—whether or not he or she resides in an area affected by yellow fever.

A blood test can be done to confirm the diagnosis by revealing the presence of antibodies that are specific to the yellow fever virus. For a person who suspects he may have the disease, it is recommended that medical help is sought immediately. This can especially be beneficial if secondary complications develop, such as pneumonia or blood infections.

Treatment & Therapy

Once a person has the disease, limited treatment is available. Medical professionals attempt to manage the symptoms. For instance, fluids could be given to combat dehydration and medication to lower a fever. However, there is not a cure for the disease itself.

Medical care can still be crucial, though, as treating the symptoms and possible complications can give the person’s body a better chance of fighting off the virus. For natives of Africa or South America, some natural immunity is gained with age.

Prevention & Prophylaxis

Prevention is the best approach to yellow fever. A yellow fever vaccine is available which provides 99% effective immunity within 30 days of a person receiving the vaccination. There are a few groups of people for whom the vaccine is not recommended, such as babies under 9 months old, people with severe egg allergies, pregnant women or breastfeeding mothers, people whose immune systems are suppressed, and sometimes people over 60 years of age. The vaccine is recommended both for people living in affected areas and those traveling there.

If a person is not able to receive the vaccine, he should practice careful mosquito bite avoidance. This is usually done by using mosquito spray and frequently reapplying it, and by wearing pants and long sleeves to minimize exposed skin. For the majority of people, the vaccine is safe, inexpensive, and provides the best possible chance of avoiding this lethal disease.