Yellow fever

Introduction

Yellow Fever is a viral disease which, like many others, is transmitted to humans by the mosquito and is preventable. This particular virus belongs to the family of flaviviruses, which are responsible for West Nile Virus, Japanese Encephalitis and Dengue Fever. Yellow Fever (YF) is confined to Tropical South America and Sub-Saharan Africa^[1]. Sub-Saharan Africa is classified as an endemic area while Tropical South America sees intermittent endemic outbreaks in forested and/or transitional areas. The disease derives its name from the yellowing of the skin and mucous membranes (jaundice) that develops in some patients. Monkeys and humans are the two primary groups being infected.

Though YF is very rare amongst travelers, many countries do require proof of vaccination, especially if you are entering from a YF endemic region.^[2]

Prevention

• Yellow Fever vaccination*
• When outdoors, use insect repellent containing 35% DEET for adults and 10% DEET for children. Follow the directions on the package.
• Many mosquitoes are most active at dusk and dawn. Be sure to use insect repellent and wear long sleeves and pants at these times or consider staying indoors during these hours.
• Avoid wearing dark coloured clothing.
• Avoid wearing perfume/cologne and scented cosmetics.

*In accordance with the World Health Organization's (WHO) regulations, YF vaccinations are available through approved Yellow Fever Vaccination Centers around the world. The single-dose vaccine will provide immunity for up to 10 years duration. Your personal physician or local health department will be able to provide you with a center in your area.^[1][3]

Symptoms and Treatment

Symptoms

Yellow Fever has an incubation period of 3-6 days post-exposure.

• A few people will exhibit no symptoms and recover without incidence.
• Most patients will enter the acute phase of the disease and exhibit flu-like symptoms (fever, headache, loss of appetite, shivering, muscle aches and nausea). Approximately 85% of these cases will show improvement after 3-4 days and their symptoms disappear, making a full recovery.
• The remaining 15% of infected patients will enter the toxic phase of the disease within 24 hours following incubation. Symptoms for this stage include (but are not limited to) fever, jaundice, abdominal pain, vomiting, and hemorrhagic bleeding.

Yellow Fever is hard to identify in the early stages of the infection. It can easily be confused with many other illnesses (influenza, malaria, hepatitis, typhoid, etc.) and laboratory analyses are required to confirm the diagnosis.^[4]

Treatment

At this time there are no specific treatments for YF. Those requiring medical attention will be treated symptomatically. Receiving the vaccine and using preventative measures against mosquitoes are the best defenses.