Yellow fever is a serious, potentially deadly flu-like disease spread by Aedes aegypti mosquitoes, which also transmit dengue and Zika viruses. It’s characterized by a high fever and jaundice. Jaundice is yellowing of the skin and eyes, which is why this disease is called yellow fever.

This disease is most prevalent in certain parts of Africa and South America. It isn’t curable, but you can prevent it with the yellow fever vaccine.

Yellow fever develops quickly, with symptoms occurring 3 to 6 days after exposure. The initial symptoms of the infection are similar to those of the influenza virus. They include:

  • headaches
  • muscle aches
  • joint aches
  • chills
  • fever

Acute phase

This phase usually lasts for 3 to 4 days. Common symptoms include:

  • headaches
  • muscle aches
  • joint aches
  • a fever
  • flushing
  • a loss of appetite
  • shivers
  • backaches

After the acute phase is over, symptoms will begin to go away. Many people recover from yellow fever at this stage, but some people will develop a more serious version of this condition.

Toxic phase

The symptoms that you experienced in the acute phase may disappear for up to 24 hours. Then, those symptoms may return, along with new and more serious symptoms. These include:

  • decreased urination
  • abdominal pain
  • vomiting (sometimes with blood)
  • heart rhythm problems
  • seizures
  • delirium
  • bleeding from the nose, mouth, and eyes

This phase of the disease is often fatal, but only 15 percent of people with yellow fever enter this phase.

Yellow fever virus (or flavivirus) causes yellow fever, and it’s transmitted when an infected mosquito bites you. Mosquitoes become infected with the virus when they bite a human or monkey with the virus. The disease can’t be spread from one person to another.

Mosquitoes breed in tropical rainforests, humid, and semi-humid environments, as well as around bodies of still water.

Increased contact between humans and infected mosquitoes, particularly in areas where people haven’t been vaccinated for yellow fever, can create small-scale epidemics.

Those who haven’t been vaccinated for yellow fever and who live in areas populated by infected mosquitoes are at risk. According to the World Health Organization (WHO), an estimated 200,000 people get the infection each year.

Most cases occur in 32 countries in Africa, including Rwanda and Sierra Leone, and in 13 countries in Latin America, including:

  • Bolivia
  • Brazil
  • Colombia
  • Ecuador
  • Peru

See your doctor right away if you’ve been traveling recently and you experience flu-like symptoms.

Your doctor will ask you about the symptoms you’ve been experiencing and if you’ve traveled recently. If your doctor suspects that you have yellow fever, they’ll order a blood test.

Your blood sample will be analyzed for the presence of the virus or for the antibodies meant to fight the virus.

There’s no cure for yellow fever. Treatment involves managing symptoms and assisting your immune system in fighting off the infection by:

  • getting enough fluids, possibly through your veins
  • getting oxygen
  • maintaining a healthy blood pressure
  • getting blood transfusions
  • having dialysis if you experience kidney failure
  • getting treatment for other infections that may develop

The WHO estimates that 50 percent of people who develop severe symptoms of this condition will die. Older adults and those with compromised immune systems are most at risk for serious complications.

Vaccination is the only way to prevent yellow fever. The vaccine for yellow fever is given as a single shot. It contains a live, weakened version of the virus that helps your body create immunity.

The yellow fever 17D vaccine is among the most effective vaccines ever made. One shot lasts a lifetime.

The Centers for Disease Control and Prevention (CDC) suggests that people between 9 months and 59 years old traveling to or living in an area where the risk of yellow fever is present should be vaccinated.

If you’re planning to travel internationally, check the CDC website to see whether you need to get any new vaccinations.

Groups of people who shouldn’t get the vaccine include:

  • people who have severe allergies to eggs, chicken proteins, or gelatin
  • infants younger than 6 months old
  • people who have HIV, AIDS, or other conditions that compromise the immune system

If you’re older than 60 and you’re considering traveling to an area that may have the virus, you should discuss vaccination with your doctor.

If you’re traveling with an infant who is 6 to 8 months old or you’re a nursing mother, you should either postpone travel to these areas if possible or talk to your doctor about vaccination.

The vaccine is considered extremely safe. The side effects may include:

  • a mild headache
  • muscle pain
  • fatigue
  • a low-grade fever

Other methods of prevention include using insect repellant, wearing clothing to reduce the number of mosquito bites, and staying inside during peak times when insects bite.