The Foreign Office has issued a fresh warning regarding the resurgence of a mosquito-borne virus that poses a high risk in 42 countries. The Travel Health Pro website, backed by the Foreign Office, released an alert this week about the spread of yellow fever in parts of Africa, Central and South America, and Trinidad in the Caribbean.
Yellow Fever: A Serious Threat
Yellow fever is a viral hemorrhagic illness that can be fatal to humans. Officials emphasize that vaccination and mosquito bite avoidance are crucial preventive measures. The virus can cause jaundice (yellowing of the skin and eyes), bleeding, and severe damage to major organs such as the liver, kidneys, and heart. The mortality rate is high among those who develop severe disease.
Current Outbreak Statistics
Travel Health Pro reported that yellow fever is a risk in areas of 13 countries and territories in South and Central America. In 2025, there were 346 confirmed human cases (including 143 deaths) from seven countries, representing a 5.6-fold increase compared to 2024. Since the start of 2026, 41 confirmed cases (including 18 deaths) have been reported from Bolivia, Colombia, Peru, and Venezuela.
In 2024, most cases were in the Amazon region. However, officials note that cases have since spread to a wider geographic area, including Sao Paulo State in Brazil and Tolima Department in Colombia. Reports also suggest recent human cases in Venezuela occurred in an area previously not considered at risk.
“Risk of YF outbreaks in South America remains high. An outbreak in Colombia has been ongoing since mid-2024, with 153 confirmed cases (including 62 deaths). The confirmed reporting of YF cases in a wider geographic area, including cases related to jungle transmission near urban centres, increases the risk of urban outbreaks,” officials stated. They added that while vaccination is highly effective, the COVID-19 pandemic has reduced vaccine coverage in local populations.
Africa: Ongoing Transmission
Yellow fever risk countries in Africa continue to report probable and confirmed cases. In 2024, confirmed cases occurred in countries with no recent history of transmission and suboptimal vaccination coverage. The World Health Organization (WHO) notes potential under-reporting due to surveillance issues. The risk remains high in endemic areas, and the mosquitoes that transmit yellow fever are common in many urban areas, increasing the risk of rapid outbreaks.
List of Countries at Risk
The WHO defines countries with a risk of yellow fever transmission. The list includes:
Africa: Angola, Benin, Burkina Faso, Burundi, Cameroon, Central African Republic, Chad*, Congo, Côte d’Ivoire, Democratic Republic of the Congo, Equatorial Guinea, Ethiopia*, Gabon, The Gambia, Ghana, Guinea, Guinea-Bissau, Kenya*, Liberia, Mali*, Mauritania*, Niger*, Nigeria, Senegal, Sierra Leone, South Sudan, Sudan*, Togo, Uganda.
Central and South America: Argentina*, Bolivia*, Brazil*, Colombia*, Ecuador*, French Guiana, Guyana, Panama*, Paraguay*, Peru*, Suriname, Trinidad and Tobago*, Venezuela*.
*Only some parts of these countries have a risk of yellow fever. Remaining areas have low potential or no risk.
Signs and Symptoms
Yellow fever varies in severity. The incubation period is three to six days. Initial symptoms include muscle pain, high temperature, headache, lack of appetite, nausea, and vomiting. Many patients improve within three to four days. However, 15 to 25 percent progress to a more serious illness within 24 hours, characterized by acute hemorrhagic fever, bleeding from the mouth, eyes, ears, and stomach, pronounced jaundice, and kidney damage. Shock and major organ failure follow, with 20 to 50 percent of these patients not surviving. Recovery grants lifelong immunity.
