What is yellow fever?
Yellow fever is a severe acute viral infection caused by the yellow fever virus, which belongs to the Flavivirus group. The disease is spread through the bites of infected mosquitoes, mainly day-biting mosquitoes. Both humans and primates can serve as reservoirs of the virus, and the risk of infection is especially significant in regions where the disease is endemic.
What are the symptoms of yellow fever?
The initial symptoms of yellow fever usually include fever, headache, muscle pain, nausea, vomiting, and weakness. In most patients, these symptoms improve within a few days, but about 15% of infected people develop a severe form of the disease with recurrent high fever, jaundice, bleeding, organ failure, and shock.
Most common symptoms
high fever;
headache;
muscle pain;
chills;
nausea or vomiting;
pronounced weakness;
in severe cases — jaundice, bleeding, kidney or other organ failure.
Where are the yellow fever risk regions?
Yellow fever is endemic in sub-Saharan Africa and tropical South America. Travelers are at greater risk if they plan to visit forests, jungle areas, savannas, or outbreak-affected regions. It is important to note that the absence of a mandatory vaccination certificate requirement does not mean that there is no yellow fever risk in that country. At the same time, some countries may require proof of vaccination even if they are not themselves endemic, in order to prevent the importation of the virus.
How does yellow fever spread?
Yellow fever spreads through the bites of infected mosquitoes. Travelers who visit forested or savanna areas in endemic regions are especially at risk if they are not vaccinated.
Yellow fever vaccine
Vaccination is the most effective way to prevent yellow fever. A single dose of the vaccine usually provides protection for life, and revaccination is generally not required. Immunity develops in most vaccinated people within 10 days after vaccination.
When is vaccination especially important?
Vaccination is generally recommended for travelers who are going to regions with a risk of yellow fever, especially if they plan to:
travel to endemic areas in Africa or South America;
stay in forest, jungle, or savanna regions;
visit outbreak-affected areas;
enter a country where proof of yellow fever vaccination is required.
International certificate of vaccination
Yellow fever vaccination is documented for international travel by the International Certificate of Vaccination or Prophylaxis (ICVP), often called the “yellow card.” The certificate becomes valid 10 days after vaccination. Under international rules, the yellow fever vaccination certificate is valid for the entire lifetime of the vaccinated person.
Is there treatment for yellow fever?
There is no specific antiviral treatment for yellow fever. Management is based on supportive care, including fluid balance, symptom control, and treatment of complications. This is why prevention and timely vaccination are especially important.
How else can the risk of infection be reduced?
Even after vaccination, travelers should still avoid mosquito bites:
use insect repellent;
wear long-sleeved clothing and long trousers;
reduce mosquito breeding sites, such as standing water;
use other personal protective measures against mosquitoes.
Because yellow fever mosquitoes often bite during the daytime, bed nets alone are not enough.
When might the vaccine not be suitable?
Yellow fever vaccine is generally not recommended for infants under 9 months of age, people with severe allergy to egg protein, people with severe immunodeficiency, or people with certain thymus disorders. In adults over 60 years of age, the benefits and risks of vaccination should be assessed individually.