Imported dengue cases reach record high
Source: gov.uk (2025-03-27)

In 2024, 904 dengue cases were reported in returning travellers across England, Wales and Northern Ireland, up from 631 in 2023.

New data from UK Health Security Agency (https://www.gov.uk/government/publications/travel-associated-infections/travel-associated-infections-in-england-wales-and-northern-ireland-2024) show imported dengue cases in England, Wales and Northern Ireland (EWNI) have reached their highest level since dengue surveillance began in 2009. All cases are linked to travel abroad.

In 2024, 904 dengue cases were reported in returning travellers across EWNI, up from 631 in 2023. Most cases were linked to travel to Southern and South-Eastern Asia. UKHSA is developing enhanced surveillance of dengue cases to better understand where people are acquiring infections and what mosquito bite precautions they were using, in order to help inform public health interventions in future.

Dengue cases have been increasing globally since 2010 with historic highs reported in 2019. In 2023, The World Health Organization (https://www.who.int/emergencies/disease-outbreak-news/item/2023-DON498) (WHO) reported a post-pandemic global increase in both dengue cases and deaths, including in regions previously considered dengue-free, with significant increases particularly noted in Asia and the Americas. A range of factors, including climate change, changing distributions of the mosquito vector, and periodic weather events leading to rising temperatures, heavy rainfall and humidity are driving this increase globally.

The Joint Committee on Vaccination and Immunisation (JCVI) has recently recommended dengue vaccination for some travellers.

Imported cases of Chikungunya, another mosquito-borne infection, have also risen in EWNI. In 2024, 112 cases were reported, more than double the 45 cases in 2023, with most linked to travel in Southern Asia. These changing patterns may reflect several factors including differences in testing practices, disease burden, global epidemiology, clinician awareness and travel trends.

Zika virus disease cases increased to 16 in England, Wales and Northern Ireland during 2024, compared to 8 cases in 2023, with most travellers returning from South-Eastern Asia. Although Zika virus cases are rarely reported and don’t often cause serious illness, the infection poses a significant risk to pregnant women, as it can be passed to the foetus. There is no drug or vaccine to prevent Zika virus infection, and the most effective way of preventing infection is minimising mosquito bites.

Mosquito-borne infections like dengue, chikungunya and Zika can cause symptoms including fever, severe headache, pain behind the eyes, muscle and joint pain, abdominal pain, loss of appetite, nausea and vomiting. These are not always present, and some people will experience no symptoms.

Dr Philip Veal, Consultant in Public Health at the UK Health Security Agency, said:

It is essential to take precautions against mosquito-borne infections such as dengue while travelling abroad. Simple steps, such as using insect repellent, covering exposed skin, and sleeping under insecticide-treated bed nets, can effectively reduce the risk of mosquito-borne infections. Before you travel, check the TravelHealthPro website for the latest health advice on your destination, including any recommended vaccinations. Even if you’ve been to a country before, remember that you don’t have the same level of protection against infections as permanent residents and are still at risk.

The Travel Health Pro (https://travelhealthpro.org.uk/) website, supported by the UK Health Security Agency, has information on health risks in countries across the world and is a one-stop-shop for information to help people plan their trip abroad. Ideally travellers should consult their GP, practice nurse, pharmacist, or travel clinic 4 to 6 weeks before their trip for individual advice, travel vaccines and malaria prevention tablets, if relevant for their destination.

In countries with insects that spread diseases (https://www.gov.uk/government/publications/mosquito-bite-avoidance-for-travellers) like dengue, malaria or Zika, travellers can protect themselves by using insect repellent, covering exposed skin, and sleeping under a treated bed net where air conditioning is not available.

It is also important for travellers to:
- ensure your routine childhood vaccines are up to date
- have any recommended travel related vaccines
- Follow the ABCD of malaria prevention- ‘Awareness of risk, Bite prevention, Chemoprophylaxis and Diagnose promptly and treat without delay’
- Carry sufficient medications to cover the whole trip
- get valid travel insurance to cover your entire trip and planned activities
As well as mosquito borne infections, UKHSA is reminding travellers that there is an ongoing outbreak of mpox in some countries in Africa. Currently, the risk to most travellers is low and vaccination against mpox infection is not recommended for the majority of people.

Those travelling to areas affected by the ongoing outbreak should take sensible precautions to protect themselves from the risk of infection by reducing touch or sexual contact, especially with individuals with a rash.

You can see a list of countries where cases of mpox clade I have been reported (https://travelhealthpro.org.uk/news/792/mpox-outbreak-in-africa-clade-1-mpox-virus-infection) on the Travel Health Pro website. We recommend that anyone planning to travel to affected countries check the latest guidance.