virus

A high number of cases were reported in the last 12 months – with a 5-fold increase in some areas – and 143 deaths

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.

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“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) reported. 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.

A big rise in infections has been detected in a report published today

Health officials have issued an alert of a ‘high risk’ of being infected with a potentially lethal virus at one of the world’s most beautiful holiday destinations. In an alert issued today (Friday March 13) the European Centre for Disease Prevention and Control said gthere has been a huge surge in cases in people returning from this hotspot.

It said that since November 2025, more than 110 travel-related cases of chikungunya virus disease have been reported by 13 EU/EEA countries among travellers returning from Seychelles. In a report today it said: “This represents a marked increase compared with

the earlier months of 2025, and no cases have been reported in preceding years. The emergence of chikungunya virus disease in the Seychelles aligns with a broader regional spread throughout the Indian Ocean. Notably, Réunion (France) experienced a major outbreak in 2025.

“According to local health authorities, chikungunya virus has become more prevalent in the Seychelles compared with other circulating arboviruses.”

Approximately 20,000 to 30,000 people from the UK travel to the Seychelles annually, with 19,870 visitors recorded in 2023. The beaches of the Seychelles have been described as being the most beautiful in the world.

The Republic of Seychelles, to give the official name, is an archipelago consisting of 115 separate islands most of which are uninhabited. The islands are set in the western part of the Indian Ocean at a distance of between 480 and 1600 km from the east coast of Africa and to the north of Madagascar. At a latitude of 4 to 10 degrees south of the equator, they form what has been described as a tropical island paradise.

The ECDC report said: “The current likelihood of chikungunya virus infection for travellers to the Seychelles is high. Given that the peak travel period to the Seychelles occurs between February and April, it is important to strengthen communication to travellers and travel medicine clinics regarding the ongoing outbreak and the need for reinforced preventive measures.

“Vaccination of travellers may be considered, based on national recommendations. The likelihood of onward transmission of chikungunya virus in mainland Europe following introduction by a viraemic traveller is currently considered low, as environmental conditions are not favourable for Aedes mosquito activity at this time of year.”

The UK Health Security Agency said: ”In 2024, there were 112 confirmed and probable cases of chikungunya reported among travellers returning to England, Wales and Northern Ireland – nearly one and a half times the number reported in 2023. Travel to India accounted for the majority of these cases, followed by travel to Pakistan and Brazil – all popular destinations for people travelling from the UK.”

It explained Chikungunya spreads through the bite of infected Aedes mosquitoes, particularly Aedes aegypti and Aedes albopictus species. Mosquitoes breed in natural and human-made sources of standing and stagnant water such blocked gutters and drains, litter, tarpaulins, open buckets, bins, plant pots and discarded items like tyres, and these are a risk factor for transmission if left around human habitation. Unlike malaria-carrying mosquitoes that are active at night, these insects are most active during the day, and particularly at dusk and dawn. This timing makes them troublesome for travellers engaged in daytime activities.

The UKHSA said: “The first symptoms of the disease are usually a high fever and severe joint pain, often more severe in the small joints or where there have been previous injuries. Many patients also experience muscle pain, headaches, sensitivity to light, and distinctive skin rashes. While most people recover fully within 1 to 2 weeks, the joint pain can persist for months or even years in some cases, with up to 12% of patients still experiencing discomfort 3 years after infection.

Serious complications are rare, occurring in approximately one in every 1,000 cases. However, certain groups face higher risks, including young babies, elderly people, and adults with underlying health conditions. Occasional complications affecting the eyes, nervous system, heart, and digestive system have been reported.”

For more information from the UKHSA click here.