Travel-associated infections in England, Wales and Northern Ireland: January to June 2025
Updated 14 August 2025
Applies to England, Northern Ireland and Wales
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Executive summary
The main findings of this report are that:
- chikungunya cases increased to 73 between 1 January and 30 June 2025, up from 27 during the same period in 2024, with most cases reporting travel to Sri Lanka, India and Mauritius, aligning with ongoing local outbreaks in countries in the Indian Ocean region
- cholera cases increased to 8 in the first six months of 2025 (up from 1 in 2024), with 4 cases linked to a single source in Ethiopia. The main travel destinations reported were Ethiopia and India
- dengue cases decreased to 161, down from 490 during the same period in 2024, with Thailand, Brazil and Indonesia as the most frequently reported travel destinations
- rickettsial infections in returning travellers decreased to 18 from 23 in the same period in 2024, with most cases reporting travel to South Africa and Thailand
- Zika virus disease cases decreased to 4 cases, down from 9 cases in the first six months of 2024, with most still associated with travel to Thailand
- Oropouche virus disease was reported for the first time in England, Wales and Northern Ireland, with 3 imported cases linked to travel to Brazil
- no cases of Japanese encephalitis or yellow fever were reported between 1 January and 30 June 2025
Background
This report, produced by the Travel Health and International Health Regulations (IHR) team in the Epidemic and Emerging Infections Directorate, UK Health Security Agency (UKHSA), summarises case numbers of selected travel-associated infections reported in England, Wales and Northern Ireland (EWNI) from 1 January to 30 June 2025. The data presented in this report supersedes any other case numbers previously reported; the data in this report is provisional: more detailed reports are produced on an annual basis and can be found via the Travel-associated infections reports landing page.
Detailed information is included on the trends of chikungunya, cholera, dengue, rickettsial infections and Zika virus disease during the first half of 2025. An infection summary and key findings are provided for Japanese encephalitis, Oropouche virus disease and yellow fever. Data presented here is collated from a variety of sources and may be subject to limitations in completeness due to various factors, including underreporting.
Detailed reports and data are available elsewhere for imported malaria cases in the UK and travel-associated enteric fever cases in EWNI.
Data sources
Data for cases of chikungunya, dengue, Japanese encephalitis, Oropouche virus disease, rickettsial infections, yellow fever and Zika virus disease was obtained from the Rare and Imported Pathogens Laboratory (RIPL), UKHSA Porton (1). Case definitions used for these infections are:
- confirmed: molecular detection (PCR, other molecular amplification test or sequencing) and/or positive virus isolation and/or seroconversion between acute and convalescent samples and/or four-fold rise in antibody titre
- probable: IgM and IgG positive and compatible clinical syndrome
Data for confirmed cholera cases was obtained from the UKHSA Gastrointestinal Bacteria Reference Unit (GBRU). A confirmed case is a person with Vibrio cholerae serogroup O1 or O139 that is positive for the cholera toxin gene (ctxA), as confirmed by the GBRU (2).
For all cases, specimen collection date was used where available to conduct analysis. In cases where this information was not available, laboratory receipt date was used. Case numbers presented in this report include both confirmed and probable cases, collated from multiple sources, including confirmed cases from GBRU, and both confirmed and probable cases from RIPL.
Geographical areas were assigned based on the patient’s residential postcode; if the patient postcode was missing, the sending laboratory postcode was used.
World regions of travel were assigned based on the United Nations world region classifications (3).
Chikungunya
Chikungunya is a mosquito-borne infection transmitted by the bite of an infected female Aedes mosquito and is caused by a virus from the Flaviviridae family. It is characterised by a sudden onset of fever usually accompanied by joint pain (arthralgia); however, symptoms vary in severity. Serious complications are uncommon, but, rarely, in older people the disease can contribute to the cause of death, particularly if there is other underlying illness. Chikungunya mainly occurs in Africa, Asia and specifically in Southern Asia, although cases have been reported in parts of Europe and North America (4).
In EWNI, there were 73 chikungunya cases reported between January and June 2025. Of these, 41 (56%) were confirmed and 32 (44%) were probable cases. This represents a 170% increase compared to the same period in 2024, which saw 27 cases (11 confirmed and 16 probable) (Figure 1).
Figure 1. Number of confirmed and probable chikungunya cases by month, January to June 2024 and 2025
Of the cases reported so far in 2025, sex and age were known for all cases. Of these, 37 cases (51%) were female (aged 10 to 82 years, median=54) and 36 (49%) were male (aged 24 to 94, median=54.5) (Figure 2).
Figure 2. Number of confirmed and probable chikungunya cases by age group and sex, January to June 2025 (n=73)
There were 73 cases reported in England, and zero cases reported in Wales and Northern Ireland. The largest proportion of cases in England were reported in London (58%) (Table 1).
Table 1. Number of confirmed and probable chikungunya cases in England, Wales and Northern Ireland by geographical distribution: January to June 2025
| Geographical area (UKHSA) | Number of cases |
|---|---|
| London | 42 |
| South East | 16 |
| West Midlands | 5 |
| East of England | 4 |
| Yorkshire and Humber | 3 |
| South West | 2 |
| North East | 1 |
| England Total | 73 |
| Wales | 0 |
| Northern Ireland | 0 |
| EWNI Total | 73 |
Between January and June 2025, travel history was known for 70 out of 73 cases, with the majority of these reporting travel to Sri Lanka (45, 64%), followed by India (9, 13%) and Mauritius (5, 7%) (Table 2).
Table 2. Number of confirmed and probable chikungunya cases by country of travel, January to June 2025
| Country of travel | Number of cases |
|---|---|
| Sri Lanka | 45 |
| India | 9 |
| Mauritius | 5 |
| Kenya | 3 |
| Thailand | 3 |
| Indonesia | 2 |
| Philippines | 2 |
| Somalia | 2 |
| Bangladesh | 1 |
| Botswana | 1 |
| Brazil | 1 |
| Ethiopia | 1 |
| Maldives | 1 |
| Réunion | 1 |
| South Africa | 1 |
| Vietnam | 1 |
| Not stated | 3 |
| Total [note 1] | 82 |
Note 1: Some cases travelled to more than one country; all countries are included here so the total may be higher than the actual number of cases.
Sri Lanka has been experiencing a large chikungunya outbreak since late 2024 – its first in 16 years (5). By March 2025, 173 chikungunya cases were reported from sentinel sites in Sri Lanka, though unofficial reports suggest higher numbers (6).
By early June 2025, over 33,000 chikungunya cases had been reported in Asia, primarily from Sri Lanka, India and Pakistan (7), reflecting wider regional transmission across the Indian Ocean, including locally acquired cases in Mauritius (8). France has also been affected, reporting 25 locally acquired cases in 2025 and major outbreaks in its overseas territories (54,233 in Reunion and 1,098 in Mayotte) by 29 June 2025 (9). No other EU/EEA country has reported locally acquired cases in 2025 so far.
Globally, an estimated 220,000 cases and 80 related deaths have been reported across 14 countries/territories since the start of the 2025 (7).
Cholera (Vibrio cholerae serogroup O1 or O139)
Cholera is caused by infection of one of 2 serogroups of the Vibrio cholerae bacteria, serogroups O1 and O139.
Cholera is an acute diarrhoeal disease caused by ingestion of contaminated food or water. A vaccine is available but is only recommended for some travellers. Clinical outcomes range from mild to acute, profuse watery diarrhoea (‘rice water stools’) and vomiting, leading to dehydration. Some infections may progress to severe disease, and in extreme cases may result in death if untreated (10). In 2024, cases were reported in 33 countries worldwide, a decrease from 45 in 2023 and 44 in 2022. The disease occurs mainly in Africa and Asia, but cases have also been reported in other regions (11).
In EWNI, there were 8 confirmed cholera cases reported between January and June 2025, up from 1 case in the same period in 2024 (Figure 3).
Figure 3. Number of confirmed cholera cases by month, January to June 2024 and 2025
Of the cases reported so far in 2025, sex and age were known for all cases. Of these, 4 cases (50%) were female (aged 28 to 55 years, median=42) and 4 (50%) were male (aged 0 to 75, median=48) (Figure 4).
Figure 4. Number of confirmed cholera cases by age group and sex, January to June 2025 (n=8)
There were 8 cases reported in England and zero cases in Wales and Northern Ireland. The largest proportion of cases in England were reported in the East Midlands (38%) (Table 3).
Table 3. Number of confirmed cholera cases in England, Wales and Northern Ireland by geographical distribution: January to June 2025
| Geographical area (UKHSA) | Number of cases |
|---|---|
| East Midlands | 3 |
| London | 2 |
| East of England | 1 |
| Yorkshire and Humber | 1 |
| South East | 1 |
| England Total | 8 |
| Wales | 0 |
| Northern Ireland | 0 |
| EWNI Total | 8 |
Between January and June 2025, travel history was known for all cases, with most of these reporting travel to Ethiopia (3, 43%) and India (3, 43%) (Table 4).
One case did not travel outside of the UK but reported drinking holy water from Ethiopia, brought back by another cholera case who also became ill (12).
Table 4. Number of confirmed cholera cases by country of travel, January to June 2025
| Country of travel | Number of cases |
|---|---|
| Ethiopia | 3 |
| India | 3 |
| Rwanda | 1 |
| Total | 7 |
Global cholera case numbers continue to be high in recent years, with the WHO Eastern Mediterranean Region recording the highest numbers in 2025, followed by the African Region, and the South-East Asia Region (13, 14).
Dengue
Dengue is a mosquito-borne infection transmitted by the bite of an infected female Aedes mosquito. It is caused by a virus from the Flaviviridae family and has 4 main serotypes: DENV-1, DENV-2, DENV-3 and DENV-4.
Illness is characterised by an abrupt onset of fever often accompanied by severe headache and pain behind the eyes, muscle pain, joint pains, nausea, vomiting, abdominal pain and loss of appetite; however, symptoms can range from mild or non-existent to severe (15). Severe dengue is rare in travellers.
Dengue is endemic in over 100 countries across Africa, the Americas, the Eastern Mediterranean, South-East Asia and the Western Pacific, with sporadic autochthonous cases occurring in France, Croatia, Italy and Spain within Europe (15, 16). Since the beginning of 2023, the World Health Organization (WHO) has reported a rise in both dengue cases and deaths in areas known for dengue risk and in regions previously considered dengue-free (15).
In EWNI, there were 161 dengue cases reported between January and June 2025. Of these, 142 (88%) were confirmed cases and 19 (12%) were probable cases. This represents a 67% decrease compared to the same period in 2024, which saw 490 cases (434 confirmed and 56 probable) (Figure 5).
Figure 5. Number of confirmed and probable dengue cases by month, January to June, 2024 and 2025
Of the cases reported so far in 2025, age was known for all cases and sex was known in 160 out of 161 cases. Of these, 80 cases (50%) were female (aged 9 to 86 years, median=34) and 80 (50%) were male (aged 0 to 75, median=43) (Figure 6).
Figure 6. Number of confirmed and probable dengue cases by age group and sex, January to June 2025 (n=160)
There were 158 cases reported in England, 3 cases in Wales and zero cases in Northern Ireland. The largest proportion of cases in England were reported in London (44%) (Table 5).
Table 5. Number of confirmed and probable dengue cases in England, Wales and Northern Ireland by geographical distribution: January to June 2025
| Geographical area (UKHSA) | Number of cases |
|---|---|
| London | 72 |
| South East | 16 |
| North West | 15 |
| East Midlands | 12 |
| East of England | 11 |
| South West | 11 |
| West Midlands | 10 |
| North East | 6 |
| Yorkshire and Humber | 5 |
| England Total | 158 |
| Wales | 3 |
| Northern Ireland | 0 |
| EWNI Total | 161 |
Between January and June 2025, travel history was known for 150 out of 161 cases, with the majority of these reporting travel to Thailand (33, 22%), Brazil (21, 14%) and Indonesia (21, 14%) (Table 6).
Table 6. Number of confirmed and probable dengue cases by country of travel, January to June 2025
| Country of travel | Number of cases |
|---|---|
| Thailand | 33 |
| Brazil | 21 |
| Indonesia | 21 |
| India | 13 |
| Tanzania | 8 |
| Sri Lanka | 8 |
| Philippines | 6 |
| Singapore | 6 |
| Cote d’Ivoire | 4 |
| Maldives | 4 |
| Nigeria | 4 |
| Kenya | 3 |
| Malaysia | 3 |
| Vietnam | 3 |
| French Polynesia | 3 |
| Other Eastern Africa | 6 |
| Caribbean | 5 |
| Other South America | 5 |
| Oceania | 4 |
| Other Western Africa | 4 |
| Other South-Eastern Asia | 3 |
| Other Southern Asia | 3 |
| Western Asia | 3 |
| Middle Africa | 2 |
| Central America | 1 |
| Eastern Asia | 1 |
| Northern Africa | 1 |
| Northern America | 1 |
| Southern Africa | 1 |
| Not stated | 8 |
| Total [note 1] | 188 |
Note 1: Some cases travelled to more than one country/region; all countries/regions are included here so the total may be higher than the actual number of cases.
Global dengue case numbers were exceptionally high throughout 2024, the highest-ever recorded number since the global dengue recording system was introduced in 2010. While global case numbers have substantially decreased in 2025 compared to the same time-period in 2024, dengue continues to occur globally with 3.6 million cases reported in the first six months of 2025. The highest case numbers have been reported in Brazil, Colombia and Indonesia (17). According to the Pan American Health Organization (PAHO), reported cases in the region have decreased by 70% compared to the same period in 2024 (18). These trends are consistent with the cases observed among travellers returning to EWNI.
Rickettsial infections
Rickettsial infections are a group of bacterial infections of the genera Orientia and Rickettsia, which are transmitted by different arthropod vectors, including ticks, mites, lice and fleas, to animals such as humans, dogs, cats and cattle. In general, the incubation period is between 6 to 14 days post infection and symptoms vary but may include fever, myalgia, headache, dry cough and rash (19, 20, 21).
Human rickettsial infections are classified into 3 main groups: spotted fever group, typhus group and scrub typhus group. Spotted fever group infections are caused by over 30 Rickettsia species such as Rickettsia africae, Rickettsia conorii sp., and Rickettsia rickettsii. They are transmitted by ticks and have a specific geographical distribution. Typhus group infections are composed of two organisms: Rickettsia typhi are transmitted to humans through flea faeces mostly in Asia, Africa and the Western Pacific; R. prowazekii are transmitted to humans through louse faeces and are associated with high density living with associated poor hygiene. Scrub typhus infections are mainly caused by Orientia tsutsugamushi and transmitted through the bite of infected mite larvae. They are most commonly found in Asia and the Western Pacific, but are now also endemic in South America and Africa, and cause an estimated 1 million cases per year (20,21).
In EWNI, there were 18 cases of rickettsial infections reported between January and June 2025. Of these, 8 (44%) were confirmed cases and 10 (56%) were probable cases. This represents a 22% decrease compared to the same period in 2024, which saw 23 cases reported (9 confirmed and 14 probable) (Figure 7). Of the reported cases in 2025, there were 10 cases (56%) in the spotted fever group, 5 cases (28%) in the typhus group and 3 cases (17%) in the scrub typhus group.
Figure 7. Number of confirmed and probable cases with rickettsial infections by month, January to June, 2024 and 2025
Of the cases reported so far in 2025, age and sex were known for all cases. Of these, 5 cases (28%) were female (aged 17 to 71 years, median=30) and 13 (72%) were male (aged 4 to 77, median=49) (Figure 8).
Figure 8. Number of confirmed and probable cases with rickettsial infections by age group and sex, January to June 2025 (n=18)
There were 16 cases reported in England, 2 cases in Wales and zero cases in Northern Ireland. The largest proportion of cases in England were reported in London (31%) (Table 7).
Table 7. Number of confirmed and probable cases with rickettsial infections in England, Wales and Northern Ireland by geographical distribution: January to June 2025
| Geographical area (UKHSA) | Number of cases |
|---|---|
| London | 5 |
| South East | 4 |
| East of England | 2 |
| North West | 1 |
| Yorkshire and Humber | 1 |
| West Midlands | 1 |
| East Midlands | 1 |
| North East | 1 |
| England Total | 16 |
| Wales | 2 |
| Northern Ireland | 0 |
| EWNI Total | 18 |
Between January and June 2025, travel history was known for all cases, with some cases travelling to more than one country. Of these, the majority of spotted fever cases reported travel to South Africa (8, 80%) (Table 8). For typhus group cases, Vietnam was the most common travel destination, with 2 cases reported.
Scrub typhus cases are tested only when travel to Southern Asia or South-Eastern Asia is reported, and of the cases so far in 2025, 2 cases travelled to Thailand and one case travelled to Bangladesh.
For all cases with rickettsial infections, the most frequently reported country of travel was South Africa (8, 44%), Thailand (3, 17%), followed by Bangladesh (2, 11%) and Vietnam (2, 11%).
Table 8. Number of confirmed and probable cases with rickettsial infections by country of travel and rickettsial group, January to June 2025
| Country of travel | Scrub typhus | Spotted fever | Typhus group | Total number of cases |
|---|---|---|---|---|
| South Africa | - | 8 | - | 8 |
| Thailand | 2 | - | 1 | 3 |
| Bangladesh | 1 | - | 1 | 2 |
| Vietnam | - | - | 2 | 2 |
| Indonesia | - | - | 1 | 1 |
| Australia | - | - | 1 | 1 |
| Cambodia | - | - | 1 | 1 |
| Chad | - | - | 1 | 1 |
| China | - | - | 1 | 1 |
| India | - | 1 | - | 1 |
| Switzerland | - | 1 | - | 1 |
| Total [note 1] | 3 | 10 | 9 | 22 |
Note 1: Some cases travelled to more than one country; all countries are included here so the total may be higher than the actual number of cases.
Zika virus disease
Zika virus disease is a mosquito-borne illness transmitted by the bite of an infected female Aedes mosquito. It is caused by a virus from the Flaviviridae family. Less commonly, transmission can occur through sexual contact, congenitally from a pregnant woman to her foetus and though blood transfusion (22).
Most people infected with Zika virus do not develop symptoms. Those that do often have mild symptoms which can include fever, headache, malaise, joint and muscle pain, a rash, itching, conjunctivitis and swollen joints (23).
Serious complications are uncommon, however, Zika virus infection can cause congenital Zika Syndrome (characterised by microcephaly and other congenital anomalies) and neurological complications such as Guillain-Barré Syndrome (23).
During 2015 to 2016, there was a large outbreak of Zika virus disease in the Americas and the Caribbean, leading to the first imported cases in the UK. As of May 2024, 90 countries across Africa, Europe, the Americas, South-East Asia and the Western Pacific have reported autochthonous Zika virus disease cases (24).
In EWNI, there were 4 Zika virus disease cases reported between January and June 2025. Of these, 2 were confirmed and 2 were probable cases. This represents a 56% decrease compared to the same period in 2024, which saw 9 cases reported, all of which were confirmed cases (Figure 9).
Figure 9. Number of confirmed and probable Zika virus disease cases by month, January to June, 2024 and 2025
Of the cases reported so far in 2025, age and sex were known for all cases. Of these, 3 cases (75%) were male (aged 34 to 54 years, median=50) and 1 (25%) was female (aged 34).
All 4 cases were reported in England, and zero cases were reported in Wales and in Northern Ireland. The largest proportion of cases in England were reported in the North West (50%) (Table 9).
Table 9. Number of confirmed and probable Zika virus disease cases in England, Wales and Northern Ireland by geographical distribution: January to June 2025
| Geographical area (UKHSA) | Number of cases |
|---|---|
| North West | 2 |
| London | 1 |
| South East | 1 |
| England total | 4 |
| Wales | 0 |
| Northern Ireland | 0 |
| EWNI Total | 4 |
Between January and June 2025, travel history was known for all cases, with the majority of these reporting travel to countries in South-Eastern and Southern Asia (75%) (Table 10). The most frequently reported country of travel was Thailand. Thailand continues to report Zika virus disease cases in 2025, with 127 confirmed cases reported so far (25). This follows an ongoing transmission of Zika virus in 2024, with 446 cases (26).
There was 1 case reporting travel to Sierra Leone – this is the first time this country has been reported as a travel destination among Zika virus disease cases in EWNI.
Table 10. Number of confirmed and probable Zika virus disease cases by country of travel, January to June 2025
| Country of travel | Number of cases |
|---|---|
| Thailand | 2 |
| India | 1 |
| Sierra Leone | 1 |
| Total | 4 |
Other travel-associated infections
Japanese encephalitis
Japanese encephalitis (JE) is a vaccine preventable mosquito-borne infection transmitted by the bite of Culex species mosquitoes. It is a flavivirus from the Flaviviridae family and is transmitted via mosquitoes to humans from pigs and water birds. Japanese encephalitis is found in 24 countries in South-Eastern Asia and the Pacific, mainly in settings where humans live in close proximity to pigs and water birds. A vaccine is available; however this is only advised for travellers at increased risk of infection. Most people with JE do not develop symptoms but for those who do symptoms may include fever and headache or vomiting in children. Less than 1% of people develop severe disease, which is characterised by encephalitic symptoms such as disorientation, seizures, coma and paralysis and approximately 30% of these cases are fatal. For cases who survive, approximately 30% suffer long term cognitive, behavioural or neurological complications (27, 28).
In EWNI there were no cases of Japanese encephalitis reported between January and June 2025. The most recently reported case was in 2023.
Oropouche virus disease
Oropouche virus disease is an infection primarily transmitted by the bite of the midge Culicoides paraensis, which is not present in the UK. Some mosquito species are competent vectors, however their contribution to disease transmission is not fully understood. Oropouche virus is a segmented single-stranded RNA virus from the Peribunyaviridae family. Most cases recover within 7 days of onset of symptoms, which include fever, headache, joint pain, muscle pain, chills, nausea, vomiting and rash (29).
Local transmission has been reported in multiple countries in South America, Central America and the Caribbean. In 2024, there was a steep increase in case numbers in the Americas and additional countries reporting cases, including some who had no transmission documented previously (30). Over 16,000 confirmed cases were recorded in the Americas, the majority from Brazil (13,785 cases, including 4 deaths). In early 2025, Brazil continued to report the highest case numbers in the region, with 3,678 cases between epidemiological weeks 1 and 4, indicating continued transmission (31).
Additionally, Oropouche virus disease cases were reported in North America and Europe in 2024 among travellers returning from countries with local transmission. Deaths from Oropouche virus infection and confirmed vertical transmission (foetal death and congenital anomaly) were both first described in 2024 in the Americas region (30).
Between January and June 2025, 3 imported cases of Oropouche virus disease were reported for the first time in EWNI, all were male adults aged 35 to 66 years with recent travel to Brazil, – consistent with ongoing high levels of transmission in Brazil. Similar imported cases were detected elsewhere in Europe in 2025, although numbers remain low. In 2024, a total of 44 imported cases were reported across EU countries, predominantly linked to travel to Cuba and Brazil (32).
Yellow fever
Yellow fever is a vaccine preventable mosquito-borne infection transmitted by the bite of multiple species of infected mosquitoes, including Aedes and Haemogogus species. Yellow fever virus is a flavivirus from the Flaviviridae family. Yellow fever is endemic in all or parts of 47 countries in Africa and Central and South America.
The incubation period ranges from 3 to 6 days. Many people do not develop symptoms but for those who do, these may include fever, headache, nausea or vomiting, muscle pain (often with backache), and loss of appetite. Most people will make a full recovery after 3 to 4 days; however, a small number (approximately 15%) will progress to a second phase of the infection and go on to develop jaundice, abdominal pain, renal failure and haemorrhage (bleeding). Up to half of infections in cases who develop severe symptoms may result in death. Yellow fever is rare in international travellers as there is a safe and effective vaccine available. Although the vaccine is safe, there have been reports of rare adverse events associated with its use (33).
In EWNI there were no cases of yellow fever reported between January and June 2025. The most recently reported case in EWNI was in 2018.
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