Key points about Yellow Fever
- Yellow fever is an acute viral disease transmitted to humans through the bite of infected mosquitoes.
- Endemic in several regions of Africa and South America, it can be responsible for epidemic outbreaks.
- The disease can progress to severe forms involving liver damage, hemorrhages and multi-organ failure, with high mortality.
- To date, there is no specific antiviral treatment for yellow fever, and management is based on symptomatic care.
- Vaccination is the most effective preventive measure and makes it possible to avoid almost all severe forms and deaths.
What is yellow fever?
Yellow fever is a viral infectious disease caused by a flavivirus, belonging to the same family as the viruses of the dengue, Zika and Japanese encephalitisIt is transmitted to humans through the bite of infected mosquitoes, mainly of the genus Aedes et haemagogusYellow fever is a hemorrhagic fever prevalent in Africa and South America. After viral inoculation, the virus multiplies in the body and can lead to systemic damage, particularly affecting the liver, kidneys, and cardiovascular system. Yellow fever is a potentially serious and fatal arboviral disease that can cause major outbreaks in endemic areas.
Yellow fever worldwide
La yellow fever is endemic in 34 African countries et 13 countries in Central and South AmericaTransmission is facilitated by the presence of mosquito vectors, tropical climatic conditions, and insufficient vaccination coverage. It is estimated that 67,000 to 173,000 severe infections and 31,000 to 82,000 deaths from yellow fever occur annually in Africa and the Americas, with Africa being the most affected continent. The exact figures are likely underestimated due to limited access to diagnosis in some regions. Three transmission cycles are described:
- le forest cycleinvolving mosquitoes and non-human primates;
- le intermediate cycleobserved in Africa, with transmission between mosquitoes and rural human populations;
- le urban cycleresponsible for epidemics, with human-to-human transmission via Aedes aegypti.
In non-endemic countries, yellow fever is observed as imported cases in unvaccinated travelers. The risk of introduction into new areas exists due to globalization and the geographic expansion of mosquito vectors.
What are the symptoms of yellow fever?
After an incubation period of 3 to 6 days, yellow fever usually begins abruptly. The initial phase includes fever, headache, generalized muscle aches, nausea, vomiting, and fatigue. These symptoms generally disappear within three to four days. In the majority of cases, the outcome is favorable after this acute phase. However, in approximately 15% of patients, the disease progresses to a severe phase after a brief remission. This is characterized by the recurrence of high fever, severe liver damage with jaundice (yellowing of the skin and eyes), gastrointestinal or mucocutaneous bleeding (oral, nasal, or ocular), kidney failure, coagulation disorders, and shock. Approximately 50% of patients with a severe form of the disease die within 7 to 10 days despite appropriate treatment.
The diagnosis of yellow fever
Diagnosis is difficult, especially in the early stages when clinical manifestations are nonspecific. In severe cases, symptoms can resemble those of malaria, leptospirosis, viral hepatitis, other hemorrhagic fevers such as dengue, and poisoning. The diagnosis is made as follows:
- at an early stage: using a reverse transcription real-time polymerase chain reaction (RT-PCR) test on a blood sample; and
- at a later stage: using antibody detection by ELISA test or plaque reduction serum neutralization test (PRNT) in a blood sample.
Further biological tests frequently reveal significant liver cytolysis, thrombocytopenia and coagulation disorders, indicating the potential severity of the infection.
Yellow fever treatments
There is no specific antiviral treatment for yellow fever. Management is based on symptomatic and supportive treatmentIdeally, this should be done in a hospital setting for moderate to severe cases. It includes maintaining vital functions, correction of hydroelectrolytic imbalances, the management of hemorrhages and liver failure ou kidneyNon-steroidal anti-inflammatory drugs (NSAIDs) and aspirin are contraindicated due to the risk of bleeding. Prevention of complications and close monitoring are essential to reduce mortality.
Prevention
Prevention of yellow fever The primary focus is on vaccination, which is highly effective. A single dose of live attenuated vaccine provides lasting protection, considered lifelong with a booster dose at least 10 years after the first injection. In addition to being medically recommended, vaccination may be administratively mandatory for travelers going to certain endemic areas, in accordance with the International Health Regulations. In France, yellow fever vaccination can only be administered at a center approved by the Regional Health Agency (ARS), such as the one at the Pasteur Institute in Lille. Mosquito control measures are an essential complement: use of skin repellents, protective clothing, mosquito nets, destruction of breeding sites, and vector control in urban areas. On a collective scale, increasing vaccination coverage in endemic countries, epidemiological surveillance, and a rapid response to outbreaks are key elements in preventing epidemics and reducing the global impact of yellow fever.
FAQ
Yellow fever is contracted through the bite of an infected mosquito, primarily in certain regions of Africa and South America. It is not transmitted directly from person to person.
Many countries, particularly in Africa and South America, require proof of yellow fever vaccination for entry. Requirements vary depending on the country and the traveler's origin.
Yes, yellow fever can progress to severe forms with liver and kidney damage and hemorrhaging, with high mortality.
There is no specific antiviral treatment for yellow fever. Treatment is symptomatic. Vaccination remains the best protection before traveling to an at-risk area.
An international vaccination center assesses the risks associated with your destination, checks your vaccinations, issues the required certificates and advises you on prevention measures adapted to your trip.
