Epidemiology
Yellow fever is an arbovirus (Flavivirus, from the Flaviviridae family, called virus amaril). This virus is transmitted to humans by the bites of female mosquitoes of the genus Aedes, which bite during the day (mostly in the early morning and at the end of the day).
Virus amaril also infects rainforest monkeys. There are 3 cycles in the transmission of the disease:
- jungle cycle (in tropical rainforests) :
- mosquito-monkey-mosquito cycle, in which humans may accidentally be contaminated.
- intermediate cycle (African savannah) :
- in which the mosquito infects both humans and monkeys.
- urban cycle :
- in which monkeys are not involved; the mosquito-human-mosquito cycle.
Yellow fever attacks the tropical zones of Africa and Latin America (Bolivia, Brazil, Colombia, Ecuador, Peru, etc.). The estimated yearly number of cases of yellow fever is 200,000 (30,000 of which are deadly).
Symptoms
The disease progresses in 2 phases :
- After a week of incubation, the first phase starts with fever or headache, shivering and muscle pain. After 2 to 3 days, most patients improve, with disappearance of symptoms.
- For 15% of patients, the disease progresses to a "toxic phase": hemorrhagic syndrome with black vomit, jaundice (whence the name "yellow fever") and renal disorders. Death occurs in 50% of cases after a phase of "delirium", seizures and coma. Others recover with no noteworthy sequelae.
All curable forms induce lifelong immunity (you cannot contract the disease again).
Treatment
No specific treatment for yellow fever. Treatment of symptoms: dehydration and fever treated with oral rehydration salts and acetaminophen. Any secondary bacterial infection must be treated with an appropriate antibiotic.
Prevention
1. Vaccination
A vaccine against yellow fever exists. It is recommended for anyone travelling to a country in which the disease is present. It involves 1 injection to be performed at least 10 days before departure. It can only be done in a licensed centre (List of licensed centres in France). It can be performed at age 9 months and up. It provides protection for 10 years. It is inadvisable during the pregnancy due to the lethal dose of the disease, except if the trip can't be postponed.
The yellow fever vaccine is required for certain countries. You will not be allowed to enter those countries without an international certificate of vaccination. It is essential for all trip in a african or american intertropical endemic zone, even in case of the lack of administrative obligation.
2. Prevention of mosquito bites
Prevention is mainly based on :
- wearing ample clothing that covers the body,
- use of appropriate repellent product for the body and insecticide product for clothing (Moustifluid High Protection Tropical Zones and Moustifluid Lotion For Fabrics and Clothing Tropical Zones),
- and repellent-sprayed mosquito nets (Moustifluid Lotion For Fabrics and Clothing Tropical Zones).
To fight the Aedes mosquito, protection must be maximised at dawn and at sunset: this is the period when the mosquito is most active, although it can also bite during the day.