Emergencies preparedness, response

Yellow fever

Nigeria launches yellow fever vaccination campaign to stop outbreak in Edo state

WHO/AFRO

20 December 2018 – The Government of Nigeria with support from WHO and partners launched this week a yellow fever reactive vaccination campaign. More than 1.4 million people from 9 months to 44-years-old are expected to be protected in this seven-day campaign, which will use part of the 3.1 million doses provided by the International Coordination Group (ICG) on Vaccine Provision, funded by Gavi, the Vaccine Alliance.

Ghana launches Sub National Immunization Days (NIDs) against yellow fever

WHO/AFRO

The Ministry of Health and the Ghana Health Service in collaboration with WHO, Gavi, the Vaccine Alliance and UNICEF has launched a sub national campaign aimed to vaccinate 5.3 million people against yellow fever in 9 regions in Ghana. The event took place in Sunyani in the Brong Ahafo Region.

The theme for the campaign is “Get vaccinated and be protected against yellow fever” and it will be conducted from Wednesday, 28th of November, to Tuesday, 4th of December, 2018. The main objective of this campaign is to maintain a high population immunity of all persons living in Ghana.

Uganda Virus Research Institute approved as a regional reference laboratory for yellow fever

WHO Uganda

26 November 2018 - The Uganda Virus Research Institute (UVRI) has been certified to perform yellow fever regional reference lab functions in the Arbovirology department that supports yellow fever diagnostic surveillance. This makes UVRI the only certified Yellow fever reference laboratory in Eastern Africa and the second in the African Region, the other being Institut Pasteur Dakar (IPD) in Senegal.

The second phase of Nigeria's biggest-ever yellow fever vaccination campaign gets underway

22 November 2018 - The Government of Nigeria – with support from WHO, Gavi, the Vaccine Alliance and UNICEF launched the second phase of the biggest-ever yellow fever preventive vaccination campaign in Nigeria. This step of the campaign, will run from 22 November to 1 December 2018 and will target 18.6 million people in the country.

Ethiopia to vaccinate more than 1 million people against yellow fever

16 November 2018 - The Ethiopian Ministry of Health, in collaboration with WHO and partners, have started a second vaccination campaign to protect high-risk populations against yellow fever. More than 1.3 million people will be protected in this seven day campaign, which follows a smaller, more focused campaign in October.

The vaccination campaign uses doses from the global emergency Yellow Fever vaccine stockpile managed by the International Coordination Group on Vaccine Provision (ICG) and funded by Gavi, the Vaccine Alliance.

2nd EYE Annual Partners Meeting: Strengthening partnership and country commitment to eliminate yellow fever epidemics

WHO

18 October 2018 - The second EYE Annual Partners Meeting was held on 11-13 September in Dakar, Senegal. The event was hosted by UNICEF WCARO and jointly organized by WHO, Gavi, and UNICEF. Partners, country representatives, vaccine manufacturers, donors, and experts came together to discuss the Eliminate Yellow Fever Epidemics (EYE) Strategy achievements to date, and what the main challenges are anticipated looking forward. Mechanisms to accelerate the EYE strategy in the implementation of immunization activities with reliable vaccine supply were the main focus of the meeting.

The Republic of Congo to vaccinate more than one million people against yellow fever

WHO AFRO

26 September 2018 - The Republic of Congo, WHO and partners have started a vaccination campaign to control the spread of yellow fever in the port city of Pointe Noire and surrounding areas. More than 1 million people from nine months of age are expected to be vaccinated in this six-day campaign.

The vaccination campaign uses doses from the global emergency yellow fever vaccine stockpile managed by the International Coordination Group on Vaccine Provision (ICG) and funded by Gavi, the Vaccine Alliance.

An updated strategy to Eliminate Yellow fever Epidemics (EYE) has been developed by a coalition of partners (Gavi, UNICEF and WHO) to face yellow fever’s changing epidemiology, resurgence of mosquitoes, and the increased risk of urban outbreaks and international spread. This global, comprehensive long term strategy (2017-2026) targets the most vulnerable countries, while addressing global risk, by building resilience in urban centres, and preparedness in areas with potential for outbreaks and ensuring reliable vaccine supply. Its strategic objectives, built on lessons learned, are:

1) Protect at-risk populations;
2) Prevent international spread;
3) Contain outbreaks rapidly.

Yellow fever is caused by a virus (Flavivirus) which is transmitted to humans by the bites of infected aedes and haemogogus mosquitoes. The mosquitoes either breed around houses (domestic), in forests or jungles (wild), or in both habitats (semi-domestic).

Occasionally, infected travellers from areas where yellow fever occurs have exported cases to countries that are free of yellow fever, but the disease can only spread easily if that country has mosquito species able to transmit it, specific climatic conditions and the animal reservoir needed to maintain it.

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. In most cases, symptoms disappear after 3 to 4 days.

A small percentage of patients, however, enter a second, more toxic phase within 24 hours of recovering from initial symptoms. High fever returns and several body systems are affected, usually the liver and the kidneys. In this phase people are likely to develop jaundice (yellowing of the skin and eyes, hence the name ‘yellow fever’), dark urine and abdominal pain with vomiting. Bleeding can occur from the mouth, nose, eyes or stomach. Half of the patients who enter the toxic phase die within 7 - 10 days.

Yellow fever is difficult to diagnose, especially during the early stages. A more severe case can be confused with severe malaria, leptospirosis, viral hepatitis (especially fulminant forms), other haemorrhagic fevers, infection with other flaviviruses (such as dengue haemorrhagic fever), and poisoning.

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.

The yellow fever virus is an arbovirus of the flavivirus genus and is transmitted by mosquitoes, belonging to the Aedes and Haemogogus species. 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 3 types of transmission cycles:

1. Sylvatic (or jungle) yellow fever: In tropical rainforests, monkeys, which are the primary reservoir of yellow fever, are bitten by wild mosquitoes which pass the virus on to other monkeys. Occasionally humans working or travelling in the forest are bitten by infected mosquitoes and develop yellow fever.

2. Intermediate yellow fever: In this type of transmission, semi-domestic mosquitoes (those that breed both in the wild and around households) infect both monkeys and people. Increased contact between people and infected mosquitoes leads to increased transmission and many separate villages in an area can develop outbreaks at the same time. This is the most common type of outbreak in Africa.

3. Urban yellow fever: Large epidemics 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 transmit the virus from person to person.

Good and early supportive treatment in hospitals improves survival rates. There is currently no specific anti-viral drug for yellow fever but specific care to treat dehydration, liver and kidney failure, and fever improves outcomes. Associated bacterial infections can be treated with antibiotics.

Yellow fever can be prevented through vaccination and mosquito control.

The yellow fever vaccine is safe and affordable, and a single dose provides life-long immunity against the disease.

Mosquito control can also help to prevent yellow fever, and is vital in situations where vaccination coverage is low or the vaccine is not immediately available. Mosquito control includes eliminating sites where mosquitoes can breed, and killing adult mosquitoes and larvae by using insecticides in areas with high mosquito density. Community involvement through activities such as cleaning household drains and covering water containers where mosquitoes can breed is a very important and effective way to control mosquitoes.


Technical information

General information

News and feature stories

A one-stop-shop for news and press releases and feature stories on yellow fever.

Videos

4 things you should know about yellow fever

Video: Yellow fever - facts and challenges

Training and learning

This course provides a general introduction to yellow fever and is intended for frontline responders engaged in preventing and managing outbreaks. The course takes approximately 1 hour to complete.

This page links all WHO information on yellow fever in Portuguese.

Subscribe to our newsletter

Contact us

For any request please send us an email to: mediainquiries@who.int

Regional information on yellow fever