New Foreign Office alert over 'fatal' virus soaring in 42 countries - full list

Travellers have been warned about the resurgence of a disease spread by mosquitos with 'high risk' in 42 countries. The Foreign Office-backed Travel Health Pro website this week issued an alert over the virus spreading in parts of Africa, Central and South America, and in Trinidad in the Caribbean. Yellow Fever can cause a serious haemorrhagic illness that can be fatal for humans . Yellow fever vaccination and mosquito bite avoidance are important preventive measures against the disease, officials said. Yellow fevefr virus can cause an illness that results in jaundice , yellowing of the skin and eyes, and bleeding with severe damage to the major organs such as liver, kidneys and heart. The mortality rate is high in those who develop severe disease. Travel Health Pro said yellow fever is a risk in areas of 13 countries and territories in South and Central America. A high number of cases were reported from this region in 2025, with 346 confirmed human cases (including 143 deaths) from seven countries. This represents a 5.6-fold increase in cases compared to 2024. Since the beginning of 2026, a total of 41 confirmed cases (including 18 deaths) have been reported from four countries: Bolivia, Colombia, Peru and Venezuela. In 2024, most yellow fever cases were reported from the Amazon region. Officials said: “While YF cases continue to be reported in this area, cases have since been reported in a wider geographic area, outside the Amazon region. This includes in Sao Paulo State in Brazil and Tolima Department in Colombia. In addition, reports suggest recent human YF cases in Venezuela have occurred in an area that had not previously been considered a risk for YF disease. “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) r eported. The confirmed reporting of YF cases in a wider geographic area, including cases related to jungle transmission near to urban centres, increases the risk of urban outbreaks [1]. While YF vaccination is one of the most successful public health interventions to prevent YF disease, the COVID-19 pandemic, among other factors, has led to a reduction of YF vaccine cover in the local population.” It added that yell;ow fever risk countries in Africa continue to report probable and confirmed cases. During 2024, confirmed cases of YF were reported in countries with no recent history of transmission and suboptimal vaccination coverage. WHO also advise that in some African countries, there may be under-reporting of YF due to surveillance and data collection issues. The risk of YF transmission remains high in endemic areas of Africa. The mosquitoes (Aedes spp.) that transmit YF are common in many urban areas in Africa. This significantly increases the risk of YF spreading, especially in heavily populated areas, which could lead to the rapid onset of YF outbreaks. Countries with a risk of yellow fever transmission as defined by the World Health Organization Africa Angola Benin Burkina Faso Burundi Cameroon Central African Republic Chad* Congo Côte d’Ivoire (Ivory Coast) 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 this country have a risk of yellow fever disease. Remaining areas either have low potential for yellow fever transmission or no risk. Signs and symptoms YF varies in severity. The infection has an incubation period (time from infected mosquito feeding to symptoms developing) of three to six days. Initial symptoms include myalgia (muscle pain), pyrexia (high temperature), headache, anorexia (lack of appetite), nausea, and vomiting. In many patients there will be improvement in symptoms and gradual recovery three to four days after the onset of symptoms. Within 24 hours of an apparent recovery, 15 to 25 percent of patients progress to a more serious illness. This takes the form of an acute haemorrhagic fever, in which there may be bleeding from the mouth, eyes, ears, and stomach, pronounced jaundice (yellowing of the skin, from which the disease gets its name), and renal (kidney) damage. The patient develops shock and there is deterioration of major organ function; 20 to 50 percent of patients who develop this form of the disease do not survive [22]. Infection results in lifelong immunity in those who recover.