Yellow Fever (Human)

Unique identifier / Notation

BI0058

Synonyms

Not found.

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Yellow fever is an acute viral haemorrhagic disease transmitted by infected mosquitoes (WHO, 2019).

Primary reference(s)

WHO, 2019. Yellow fever. World Health Organization (WHO). Accessed 18 November 2019.

Additional scientific description

Yellow fever virus is an arbovirus of the flavivirus genus and is transmitted by mosquitoes, belonging to the Aedes and Haemogogus genus. The different mosquito species live in different habitats – some breed around houses (domestic), others in the jungle (wild), and some in both habitats (semi-domestic). There are three types of transmission cycles: sylvatic (or jungle) yellow fever; intermediate yellow fever; and urban yellow fever. The virus is endemic in tropical areas of Africa and Central and South America (WHO, 2019).

The ‘yellow’ in the name refers to the jaundice that affects some patients (WHO, 2019).

Once contracted, the yellow fever virus incubates in the body for 3 to 6 days. Many people do not experience symptoms, but when these do occur, the most common are fever, muscle pain with prominent backache, headache, loss of appetite, and nausea or vomiting. Symptoms disappear after 3 to 4 days (WHO, 2019).

A small proportion of patients may enter a more toxic phase within 24 hours of recovering from initial symptoms. High fever returns and usually the liver and the kidneys are affected. People in this phase are likely to develop jaundice (yellowing of the skin and eyes), dark urine and abdominal pain with vomiting. Bleeding can occur from the mouth, nose, eyes or stomach. Half of the patients in this toxic phase die within 7 to 10 days (WHO, 2019).

Polymerase chain reaction (PCR) testing in blood and urine can sometimes detect the virus in early stages of the disease. In later stages, testing to identify antibodies is needed (WHO, 2019).

The World Health Organization (WHO) has published guidance on case classification and surveillance standards (WHO, 2015).

Metrics and numeric limits

Not available.

Key relevant UN convention / multilateral treaty

International Health Regulations (2005), 3rd ed. (WHO, 2016).

Examples of drivers, outcomes and risk management

Major epidemics of yellow fever occur when infected people introduce the virus into heavily populated areas with high mosquito density and where most people have little or no immunity, due to lack of vaccination. In these conditions, infected mosquitoes of the Aedes aegypti species transmit the virus from person to person (WHO, 2019).

Yellow fever is prevented by an extremely effective vaccine, which is safe and affordable (WHO, 2019). However, there is no specific antiviral therapy, so if severe illness develops, only supportive care is available. The risk of yellow fever transmission in urban areas can be reduced by eliminating potential mosquito breeding sites, including by applying larvicides to water storage containers and other places where standing water collects (WHO, 2019).

Both vector surveillance and control are components of the prevention and control of vector-borne diseases, especially for transmission control in epidemic situations (WHO, 2019).

Prompt detection of yellow fever and rapid response through emergency vaccination campaigns are essential for controlling outbreaks (WHO, 2019).

Occasionally travellers who visit yellow fever endemic countries may carry the disease to countries free from yellow fever. In order to prevent importation of the disease, many countries require proof of vaccination against yellow fever before they will issue a visa, particularly if travellers come from, or have visited yellow fever endemic areas (WHO, 2019).