The UK Health Security Agency (UKHSA) has urged holidaymakers to protect themselves against mosquito-borne diseases and other travel-related infections after new figures showed
imported cases of dengue and Zika continuing to rise as the summer travel season begins.
Provisional data covering England, Wales and Northern Ireland found that 137 dengue cases were reported between January and June 2026, with South-East Asia and South Asia remaining the main locations where infections were acquired. Thailand accounted for 27 cases, while 19 were linked to travel to the Maldives.
Health officials also recorded eight imported cases of Zika virus during the first half of the year, already exceeding the seven reported throughout the whole of 2025. Indonesia accounted for half of this year's cases, marking a notable increase after only one travel-related infection linked to the country had been reported between 2014 and 2025.
Although Zika infection is usually mild, the virus poses a significant risk during pregnancy because it can be passed to an unborn baby and cause serious birth defects. There is currently no vaccine or specific treatment.
The latest surveillance data also showed 59 imported chikungunya cases between January and June, with Sri Lanka accounting for 18 infections.
Meanwhile, 557 malaria cases were reported across England, Wales and Northern Ireland between January and May. Malaria can be life-threatening but is largely preventable through the correct use of anti-malarial medication and measures to avoid mosquito bites.
UKHSA said the figures followed the seasonal pattern seen in previous years, with imported mosquito-borne infections typically increasing during the spring and summer holiday period. Dengue reached its highest monthly total of 2026 in June, while Zika infections continued to be detected throughout the spring.
The agency also warned of an increase in travel-related cases of enteric fever, which includes typhoid and paratyphoid fever. A total of 287 cases were reported during the first six months of the year. The illnesses, caused by Salmonella bacteria, are usually spread through contaminated food or water and typically peak between May and October. In 2025, September recorded the highest monthly total with 118 cases.
Health officials expect imported infections to rise further over the coming weeks as overseas travel reaches its seasonal peak.
Dr Hilary Kirkbride, Consultant Epidemiologist and Head of Travel Health at UKHSA, said:
“Summer is a popular time to travel – don’t let illness spoil your holidays. Good preparation and planning is important for a safe and enjoyable trip.
Check the TravelHealthPro website for the latest health advice for your destination, including which vaccines you may need and any important medications, such as antimalarial tablets. To protect against mosquito borne infections use insect repellent, cover exposed skin and sleep under a treated bed net where needed. For enteric fever and other stomach bugs make sure you take good food and water hygiene precautions.
Even if you have visited a country before, you do not have the same level of natural protection against infections as permanent residents, so it is important to take precautions every time you travel. And if you are pregnant or trying to conceive there are special precautions you should take, so please speak to a doctor, nurse or local travel clinic before planning your trip”.
Separately, UKHSA reminded families that measles continues to circulate in parts of the UK and in several countries overseas. The highly contagious virus can lead to serious complications, including pneumonia and, in rare cases, inflammation of the brain.
The agency urged parents to ensure children are fully protected with two doses of the MMR or MMRV vaccine before travelling, noting that babies under one year old and some people with weakened immune systems cannot receive the vaccine and rely on high vaccination rates within the wider community for protection. Photo by gov.uk
