Yellow Fever
- Acute viral haemorrhagic disease transmitted by infected mosquitoes
- The name refers to the yellow colour of jaundice experienced by infected humans
- Yellow fever is a tropical disease, endemic in western and central Africa, and also in the
rainforests of South America
- During 2013, the epidemiological burden of yellow fever was 84, 000 to 170, 000 cases,
with an estimated 29, 000 to 60, 000 deaths
Pathophysiology
- The causative agent is the yellow fever virus, an arbovirus of the genus Flavivirus
- Transmission is zoonotic, specifically arthropod-borne, by the mosquito Aedes aegypti
- In urban areas, humans are a reservoir host, with mosquitoes transmitting the virus
between humans. Also, in rainforest areas, transmission to humans during tree felling,
where monkeys are reservoir hosts (via mosquitoes), also occurs
- Once the virus is contracted, it will incubate in the body for 3-6 days. Many patients are
asymptomatic
- The main clinical features of mild yellow fever infection are proteinuria, leucopenia and
jaundice, without any complications
- In other cases, the infection can be severe, and presents as fever, muscle pain and
headaches
- In some patients, this is followed by a ‘toxic phase’ within 24 hours of recovery from initial
symptoms. In this phase, fever returns, accompanied by jaundice, dark urine, abdominal
pain with vomiting and bleeding from the mouth, nose, eyes and stomach. Patients usually
die within 7 – 10 days of infection
Diagnosis
- Yellow fever can be difficult to diagnose in the early stages, and more severe cases can be
confused with malaria, leptospirosis and viral hepatitis
- The virus can be isolated from the blood using tissue culture; however, polymerase chain
reaction (PCR) testing of blood and urine is more common and is especially used in
detecting the early stages of the disease
- In later stages of the disease, immunostaining and antibody testing (PRNT and ELISA) is
needed
Treatment and prevention
- Whilst there is no specific anti-viral treatment for yellow fever, specific care to treat
dehydration, liver/ kidney failure and fever does improve outcomes of the patients
- The yellow fever vaccine is the best way to prevent infection
- Acute viral haemorrhagic disease transmitted by infected mosquitoes
- The name refers to the yellow colour of jaundice experienced by infected humans
- Yellow fever is a tropical disease, endemic in western and central Africa, and also in the
rainforests of South America
- During 2013, the epidemiological burden of yellow fever was 84, 000 to 170, 000 cases,
with an estimated 29, 000 to 60, 000 deaths
Pathophysiology
- The causative agent is the yellow fever virus, an arbovirus of the genus Flavivirus
- Transmission is zoonotic, specifically arthropod-borne, by the mosquito Aedes aegypti
- In urban areas, humans are a reservoir host, with mosquitoes transmitting the virus
between humans. Also, in rainforest areas, transmission to humans during tree felling,
where monkeys are reservoir hosts (via mosquitoes), also occurs
- Once the virus is contracted, it will incubate in the body for 3-6 days. Many patients are
asymptomatic
- The main clinical features of mild yellow fever infection are proteinuria, leucopenia and
jaundice, without any complications
- In other cases, the infection can be severe, and presents as fever, muscle pain and
headaches
- In some patients, this is followed by a ‘toxic phase’ within 24 hours of recovery from initial
symptoms. In this phase, fever returns, accompanied by jaundice, dark urine, abdominal
pain with vomiting and bleeding from the mouth, nose, eyes and stomach. Patients usually
die within 7 – 10 days of infection
Diagnosis
- Yellow fever can be difficult to diagnose in the early stages, and more severe cases can be
confused with malaria, leptospirosis and viral hepatitis
- The virus can be isolated from the blood using tissue culture; however, polymerase chain
reaction (PCR) testing of blood and urine is more common and is especially used in
detecting the early stages of the disease
- In later stages of the disease, immunostaining and antibody testing (PRNT and ELISA) is
needed
Treatment and prevention
- Whilst there is no specific anti-viral treatment for yellow fever, specific care to treat
dehydration, liver/ kidney failure and fever does improve outcomes of the patients
- The yellow fever vaccine is the best way to prevent infection
