April 18, de 2024 Author: Saraiva da Cunha Yellow fever is a serious infectious hemorrhagic disease, with a high mortality rate. It is caused by a virus and is transmitted to people by mosquitoes infected by the virus. The yellow fever virus belongs to the Flavivirus genus. Mosquitoes become infected when they bite people who are infected with the yellow fever virus. The main species of mosquito that carries the disease is Aedes aegypti, which also transmits the Dengue and Zica viruses. These mosquitoes live and breed close to human habitats, lay eggs in natural or artificial standing water, bite during the day and fly short distances. Preventing yellow fever must be a priority when traveling to countries in South America and Sub-Saharan Africa. In 2023, yellow fever was endemic in 47 countries of Afric and Central and South America. It is possible that people infected by the virus are the source of the disease in areas where the disease is not endemic, as long as the mosquito species responsible by the transmission exists in those areas. The disease is not transmitted directly from person to person. Symptoms and treatment After infection, the incubation period lasts 3 to 6 days. The initial symptoms of the disease are: Fever; Headache and muscle pain; Loss of appetite, nausea, and vomiting. These symptoms, which are common to many other illnesses, may disappear in 3-4 days. However, in some people a more serious disease presentation follows, which can affect several body systems with organ failure, bleeding, and death within 7-10 days. A definitive diagnosis of yellow fever needs laboratory tests to search for the virus or antibodies against the virus, which can develop following exposure to the virus or vaccination. There are no specific antiviral medications to treat yellow fever. Treatment of the disease is based on symptom control and support measures. Yellow fever prevention Yellow fever prevention is based on: Vaccination; Control of transmitting mosquitoes. Vaccination is the safest way to prevent the disease, both in people traveling to risk areas and in local populations. Vaccine immunity develop quickly: after 10 days in 90% of vaccinated people and within 30 days in 99% of vaccinated people; The vaccine has been used for many years and has a good safety profile. Preventing mosquito bites plays an irreplaceable role: In countries where vaccination coverage is low; In people who for some reason cannot be vaccinated; After vaccination, until vaccine immunity develops. In other situations, preventing mosquito bites reinforces prevention: Wear protective clothing that does not leave areas of skin exposed; Apply mosquito repellent products; Avoid being outside during the day, especially at dawn and dusk; Protect environment indoor with nets, fans and air conditioning; Eliminate standing water, especially near rooms. Vaccination of travelers In Portugal, vaccination of travelers against yellow fever must be determined in a prior medical consultation, and is based on parameters such as age, physiological state, personal health history and other particularities, as well as the destination, especially when it comes to countries in Central and South America and Africa. The administration of the yellow fever vaccine in Portugal is carried out at international vaccination centers that exist throughout the country. The vaccine can be administered from 9 months of age. Except in specific circumstances, the World Health Organization considers that the administration of one dose of the vaccine protects adults for life. For children under 2 years of age, the vaccine protection is shorter, and a booster dose may be necessary. Proof of vaccination against yellow fever, with the International Certificate of Vaccination, may be required to enter: In countries where yellow fever is endemic; In many countries where yellow fever does not exist, whenever there has been recent travel to areas where the disease is endemic. World Health Organization strategy The World Health Organization strategy for controlling yellow fever is based on: Protection of local populations, recommending inclusion of yellow fever vaccine in routine vaccination programs in countries where the disease is endemic. Preventing the spread of the disease to areas where it is not endemic. Early identification and control of outbreaks. Source: Schnyder JL, de Jong HK, Bache BE, et al. Long-term immunity following yellow fever vaccination: a systematic review and meta-analysis. Lancet Glob Health 2024;12:e445-6. World Health Organization, Yellow fever . Meet the Infectious Diseases clinical team at the Hospital da Luz network. The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
