Diseases spread by mosquitoes, including Zika virus and dengue, have been on the increase in the UK this year, prompting a warning to those heading on holiday this summer.
The UK Health Security Agency (UKHSA) said these diseases, spread by mosquitoes, can be harmful to people and the experts said measures should be taken to protect holidaymakers.
It urged travellers to use insect repellent, wear long sleeves and trousers and sleep under a treated bed net if necessary. People should also get any jabs they need for travel and check whether they need malaria tablets.
The UKHSA said eight Zika virus cases were reported from January to June 2026 – already above the seven cases recorded in the whole of 2025. Four of these were from Indonesia.
Some 137 cases of imported dengue were reported in England from January to June this year, with South-East Asia and South Asia remaining the most common regions where people caught it. Some 27 cases were linked to travel to Thailand and 19 to the Maldives. For comparison, the overall number of cases by the end of June last year was 161, though cases also tend to rise later in the year.
A total of 59 chikungunya cases were reported from January to June this year, with Sri Lanka being the most commonly reported country of travel, accounting for 18 cases. There were 73 in the same period last year.
Meanwhile, 557 malaria cases were reported in England, Wales and Northern Ireland from January to May. Last year at the same point, there were 548.
As well as mosquito-borne illnesses, there were 287 cases of typhoid and paratyphoid fever between January and June this year.
Typhoid and paratyphoid are caused by Salmonella bacteria, which is usually spread through contaminated food or water. Mosquitoes rely on standing water to lay their eggs. It then needs to be warm enough for the eggs to hatch, which can take just a few days if temperatures are high enough.
What are the symptoms of dengue fever, chikungunya, Zika and malaria?
Dengue fever can feel similar to flu and symptoms include high temperature, severe headache, pain behind the eyes, muscle and joint pain and feeling sick.
Chikungunya symptoms include fever, joint pain, headache, muscle pain, joint swelling and rash.
Most people with Zika suffer a mild illness, but it is serious in pregnant women and can cause stillbirth, miscarriage, problems with development and unusually small heads.
Meanwhile, malaria can prove fatal, with symptoms including fever, vomiting and pain.
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 anti-malarial 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.”
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