Yellow fever profile

[Sally Furniss]

<table border="0" cellpadding="0" cellspacing="0" width="100%"><tbody><tr><td>Disease profile

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</td></tr></tbody></table> Yellow fever is an acute viral infection of short duration and varying severity. The disease occurs in two forms -- urban and sylvatic (jungle) yellow fever. Both forms are caused by the same virus, which is a member of the Flaviviridae family of viruses. Transmission

Yellow fever is transmitted to humans by the bite of infected mosquitoes from a variety of species, principally the Aedes and Haemagogus species. These mosquitoes are day-time biters.
<table border="0" cellpadding="0" cellspacing="0" width="100%"><tbody><tr><td>Geographic distribution

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</td></tr></tbody></table> Yellow fever is constantly present (i.e., endemic) in many tropical areas of South America and Africa. From time to time in endemic areas, the number of yellow fever cases can increase dramatically to the epidemic level. For the most part, yellow fever transmission is restricted to rural and jungle areas.
<table border="1" cellpadding="2" cellspacing="0" width="100%"> <tbody><tr> <td colspan="3" class="bg-grey-light">Table 1: Countries where yellow fever occurs</td> </tr> <tr> <td valign="top" width="33%">Angola
Benin
Bolivia
Brazil
Burkina Faso
Burundi
Cameroon
Central African
Republic
Chad
Colombia
Congo
Côte d'Ivoire
Democratic Republic
of the Congo
(formerly Zaire)
Ecuador
</td> <td valign="top" width="33%">Equatorial
Guinea
Ethiopia
French Guiana
Gabon
Gambia
Ghana
Guinea
Guinea-Bissau
Guyana
Kenya
Liberia
Mali
Niger
Nigeria
Panama
Peru </td> <td valign="top" width="34%">Rwanda
Sao Tome &
Principe
Senegal
Sierra Leone
Somalia
Sudan
Suriname
Tanzania, United
Republic of
Togo
Uganda
Venezuela
Zambia</td> </tr><tr><td colspan="3"> Source: World Epidemiological Record (WER), vol. 75, No. 41 (Oct. 13, 2000), World Health Organization
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<table border="0" cellpadding="0" cellspacing="0" width="100%"><tbody><tr><td>Symptoms

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</td></tr></tbody></table>Some infected individuals have no symptoms. When they do occur, symptoms take 3 to 6 days to appear and range from self-limiting fever to sudden onset of fever with chills, headache, muscle pain (back pain), loss of appetite, nausea and/or vomiting. In severe cases, yellow fever can lead to shock, bleeding, organ failure, jaundice (i.e., yellowing of skin and eyes) and death.

<table border="0" cellpadding="0" cellspacing="0" width="100%"><tbody><tr><td>Treatment

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</td></tr></tbody></table> There is no specific treatment for yellow fever. The overall case-fatality rate may reach 20% to 40% in single outbreaks. Deaths from yellow fever have been reported among unvaccinated travellers.
Vaccine

The single-dose 'live' vaccine for yellow fever is safe, effective and recommended for individuals 9 months of age and older. The vaccine becomes protective after 10 days, and provides immunity to a vaccinated individual for 10 years or more. For individuals who are pregnant, immuno-suppressed or allergic to eggs, the yellow fever vaccination may not be recommended.

Mosquito-control precautions
Taking the following personal precautions may reduce the risk of exposure to day-time biting mosquitoes:

• remain in well-screened or completely enclosed, air-conditioned areas;
• wear light-coloured clothing with full-length pant legs and sleeves; and
• use insect repellent on exposed skin.

The use of insect repellent on exposed skin is strongly recommended. Of the insect repellents registered in Canada, those containing 'N, N diethyl-m-toluamide' (DEET) are the most effective. Although the concentration of DEET varies from product to product, repellency rates are largely equivalent. In general, higher concentrations protect for longer periods of time, but there is little advantage in the duration of repellence with DEET concentrations greater than 50%, and there may be additional risk of toxicity with higher concentrations. New micro-encapsulated products containing 33% DEET are registered in Canada, and they should provide up to 8 hours of protection.
Children and DEET
In rare instances, application of insect repellents with DEET has been associated with seizures in young children (only 14 cases over 30 years of DEET use and billions of applications every year). The actual concentration of DEET varies among repellents and can be as high as 95%. However, repellents with DEET concentrations of 10% are very effective and should last 3 to 4 hours. Therefore, for children, DEET in a concentration of 10% or less should be applied sparingly to exposed surfaces only and washed off after children come indoors.
The likelihood of adverse reactions can be minimized by the following precautions:

• apply repellent sparingly and only to exposed skin;
• avoid applying high concentration products;
• avoid applying repellents to portions of children's hands that are likely to contact the eyes or mouth;
• never use repellents on wounds or irritated skin; and
• wash repellent-treated skin after children come indoors. If a reaction to insect repellent is suspected, wash treated skin and seek medical attention.

In Canada, DEET products are not recommended for use in children less than 2 years of age. For more information on insecticide use, go to: Safety Tips on Using Personal Insect Repellent

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For more information...

• Visit the World Health Organization - information on yellow fever
  
• and online publication Yellow fever
  
  Written by: Dr. Jari Vainio and Dr Felicity Cutts, London School of Hygiene and Tropical Medicine
• District guidelines for yellow fever surveillance
  
  WHO
• For maps of yellow fever-endemic area, visit Centers for Disease Control and Prevention
  
  , USA
• For more Know before you go! information, click here.

http://www.phac-aspc.gc.ca/tmp-pmv/info/yf_fj_e.html