Yellow Fever

Yellow Fever

Mandatory vaccination against yellow fever is carried out to prevent the importation of yellow fever virus into vulnerable countries. These are countries where yellow fever does not occur but where the mosquito vector and non-human primate hosts are present. Importation of the virus by an infected traveller could potentially lead to the establishment of infection in mosquitoes and primates, with a consequent risk of infection for the local population. In such cases, vaccination is an entry requirement for all travellers arriving from countries, including airport transit, where there is a risk of yellow fever transmission. If yellow fever vaccination is contraindicated for medical reasons, a medical certificate is required for exemption.

The International Certificate of vaccination or revaccination against Yellow fever is valid only if the vaccine used has been approved by the World Health Organization and if the vaccinating center has been designated by the Health administration for the territory in which that center is situated.

The validity of this certificate shall extended for period of ten years, beginning ten days after the date of vaccination or, in the event of a revaccination within such period of ten years, from the date of that revaccination.

This certificate must be signed by in his own hand by a Medical practitioner or other person authorized by the National Health Administration; his official stamp is not an accepted substitute for his signature.

Any amendment of this certificate, or erasure, or failure to complete any part of it, may render it invalid.

International certificate of vaccination or revaccination against yellow fever Certificate international de vaccination ou de revaccination center la fièvre jaune

Yellow fever is a life-threatening viral infection transmitted by mosquitoes in parts of Africa and South America. In urban areas, yellow fever is primarily a disease of humans and is transmitted from person to person by Aedes mosquitoes, which breed in man-made water containers, such as jars, barrels, cisterns, and discarded tires. Because Aedes mosquitoes proliferate in densely populated areas, large outbreaks may occur. However, except during epidemics, yellow fever is rare in urban settings.

In the jungle, yellow fever is mainly a disease of non-human primates and is transmitted by a variety of mosquito species. Human cases occur sporadically, chiefly among those who work in the jungle, such as loggers. In the humid or semi-humid savannahs of Africa, an intermediate situation exists, wherein both monkeys and humans are infected and the disease occurs in many small villages simultaneously, but not at the levels seen in urban epidemics. This has been the pattern for most yellow fever outbreaks reported in recent years.

The incubation period ranges from three to six days. Initial symptoms may include fever, chills, headache, muscle aches, backache, loss of appetite, nausea and vomiting, which usually subside in three or four days. However, after initial improvement, approximately one person in six enters a second, toxic phase characterized by recurrent fever, vomiting, listlessness, jaundice, kidney failure, and hemorrhage, leading to death in up to half of the cases. There is no treatment except for supportive care.

Yellow fever vaccine should be given at least ten days prior to arriving in a yellow-fever-endemic area and must be administered at an approved yellow fever vaccination center, which gives each vaccinee a fully validated International Certificate of Vaccination. The vaccine is given as a single 0.5 cc subcutaneous injection. A booster dose is recommended every 10 years for those who remain at risk. Reactions to the vaccine, which are generally mild, may include headaches, muscle aches, low-grade fevers, or discomfort at the injection site. Severe allergic reactions to yellow fever vaccine are uncommon and occur principally in those allergic to eggs.

Rarely, yellow fever vaccine may lead to multiple organ system failure, similar to yellow fever caused by wild-type virus, or to neurologic illness. A recent report indicates that those with a history of thymus disease or thymectomy are at highest risk for developing multiple organ system failure and should not be given yellow fever vaccine . Limited data also suggest that serious adverse reactions occur more commonly among the elderly and among those receiving yellow fever vaccine for the first time.

Because yellow fever vaccine contains live virus, it should not in general be given to children under 9 months of age, pregnant women, and immunosuppressed individuals, such as those with AIDS or cancer patients receiving immunosuppressive medications. These individuals should avoid traveling to areas where yellow fever is actively transmitted. Physicians considering yellow fever vaccine for pregnant women or infants between the ages of six and nine months because of special circumstances should contact the Division of Vector-Borne Infectious Diseases.