Yellow fever is an acute vaccine preventable viral haemorrhagic
disease found mainly in tropical regions of
Africa and America. It is caused by a Flavivirus which is
transmitted by mosquito bites and has a natural reservoir
in non-human primates. The virus is endemic in
tropical areas of Africa and Latin America, with a combined
population of over 900 million people [1]. The
“yellow” in the name refers to the jaundice that affects
some patients. Approximately 200,000 cases and 30,000
deaths occur annually especially in Africa [2] where the
case-fatality rate ranges from 15–50% [3]. The yellow
fever virus can cause devastating epidemics of potentially
fatal, hemorrhagic disease. The disease can be confirmed
through, serological testing by way of ELISA for
yellow fever virus-specific IgM or isolation of the virus
from blood samples. These are the recommended standard
diagnostic tests for yellow fever although PCR tests
which detect the viral genetic material have been used
[1,4]. The number of yellow fever cases has increased
over the past two decades due to declining population
immunity to infection, deforestation, urbanization, population
movements and climate change. This disease has no
cure and treatment is symptomatic, aiming at reducing
symptoms for the comfort of the patient and mass vaccination
is the most important preventive measure [5].
Immunization of people at risk interrupts human to human
transmission of the yellow fever virus especially when
adequate vaccination coverage levels are reached. The vaccine
is safe, affordable and highly effective, and appears to
provide protection for 30–35 years or more [1]. The vaccine
provides effective immunity within one week for 95%
of persons vaccinated [6,7]. Despite mass vaccination campaigns
to prevent and control these outbreaks, the risk of
major yellow fever epidemics, especially in densely populated,
poor urban settings, both in Africa and South
America, has greatly increased [8]. Consequently, yellow
fever is considered an emerging, or reemerging disease of
considerable importance.