Research and analysis

Travel-associated infections in England, Wales and Northern Ireland: 2024

Updated 27 March 2025

Applies to England, Northern Ireland and Wales

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). The data presented in this report supersedes any other case numbers previously reported.

Detailed information is included on the trends of chikungunya, cholera, dengue, rickettsial infections and Zika virus disease in 2024. 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 annual reports 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, rickettsial infections, yellow fever, Oropouche virus disease and Zika virus disease were 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 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.

Residential postcodes are not available for all cases and where unavailable, local diagnostic laboratory postcode is used. This means that EWNI residents as well as non-residents may be included in this report.

Data for UK residents and UK overseas visitors, including 2023 travel trends, was obtained from the Office of National Statistics (ONS)  (3).

World regions of travel were assigned based on the United Nations world region classifications (4).

Travel to and from the UK in 2023

Travel trend data obtained from the ONS International Passenger Survey represents the most up-to-date information available.

In 2023, UK residents made 86.2 million visits abroad, a 21% increase compared to 71.0 million in 2022. There were 38.0 million visits made by overseas residents to the UK, a 22% increase compared to 2021 (31.2 million). Travel to and from the UK in 2023 still remains below the peak in 2019, before the start of the COVID-19 pandemic (Figure 1) (5). Similar to during 2022, most travel occurred during the third quarter of the year (July to September).

The most popular reasons for travel by UK residents in 2023 were holidays, with 55.5 million visits, followed by visiting friends and relatives (22.5 million) and business travel (6.3 million). Of these, only figures for those visiting friends and relatives have returned to levels seen in 2019. The top 5 most visited countries were Spain, France, Italy, Greece and Portugal, the same as in 2022.

Holiday travel was also the most popular reason for overseas residents visiting the UK in 2022, with 15.9 million visits, followed by visiting friends and relatives (12.8 million) and business travel (6.5 million), similar to 2022. The number of holiday visits are now at a level comparable to 2019. Residents of the USA, France, Germany, Republic of Ireland and Spain represented the highest numbers of overseas residents visiting the UK (3), the same countries as seen in 2022.

Figure 1. Visits to and from the UK: from 2014 to 2023

Travel-associated infections 2020 to 2024

Table 1. Travel-associated infections in England, Wales and Northern Ireland (EWNI): 2020 to 2024

Disease (Organism)*	2020	2021	2022	2023	2024
Chikungunya	33	17	31	45	112
Cholera (Vibrio cholerae serogroup O1 or O139)	2	2	20	14	9
Dengue	91	97	446	631	904
Japanese encephalitis	-	-	-	1	-
Oropouche virus disease	-	-	-	-	-
Rickettsial infections	12	4	31	42	44
Yellow Fever	-	-	-	-	-
Zika virus disease	1	1	8	8	16

*only includes confirmed and probable cases

Table 1 presents reported travel-associated infections in England, Wales, and Northern Ireland from 2020 to 2024. Dengue remains the most frequently reported infection, with cases continuing to rise from 631 in 2023 to 904 in 2024, the highest since surveillance began in 2009. Similarly, there was a large increase in reports of chikungunya in 2024, with over double the number of cases compared to 2023. The reasons for these trends are multifactorial and include changes in testing and ascertainment, disease burden and global epidemiology, clinician awareness, travel patterns, interruptions in global vector control programmes, and the geographical spread of Aedes mosquitoes.

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 there have been cases reported in parts of Europe and North America (6).

In EWNI, there were 112 chikungunya cases reported in 2024, of which 55 (49%) were confirmed cases and 57 (51%) were probable cases. This is nearly one and a half times the number of cases reported in 2023 (n=45). Case numbers were lower in the first two quarters of 2023 (n=8, n=19) and the majority of cases were diagnosed in the third and fourth quarters (n=45, n=40) (Figure 2).

Figure 2. Number of chikungunya cases by quarter, Q1 2020 to Q4 2024

In 2024, age and sex were known for 109 out of 112 cases. Of these, 58 cases (53%) were female (aged 5 to 71 years, median=44) and 51 (47%) were male (aged 11 to 74, median=48) (Figure 3).

Figure 3. Number of chikungunya cases by age group and sex, 2024 (n=112)

In 2024, there were 105 cases reported in England, four cases in Wales and three cases in Northern Ireland. This is the first time a case has been reported in Wales since 2021 and in Northern Ireland since 2020. The largest proportion of cases in England were reported in London (41%) (Table 1).

Table 2. Number of chikungunya cases in England, Wales and Northern Ireland by geographical distribution, 2024

Geographical area	Number of cases
London	43
South East	19
West Midlands	12
North West	8
East of England	7
South West	7
North East	4
Yorkshire and Humber	3
East Midlands	2
England total	105
Wales	4
Northern Ireland	3
EWNI Total	112

In 2024, travel history was known for 110 out of 112 cases, with the majority of these reporting travel to Southern Asia (88 cases, 80%), followed by South-Eastern Asia (11 cases, 10%) and South America (7 cases, 3%). The most frequently reported country of travel for chikungunya cases was India (66 cases), followed by Pakistan (11 cases) and Brazil (7 cases) (Table 3).

Cases who travelled to India reported travelling to a number of regions including Karnataka, Maharashtra, Telangana, Tamil Nadu, Punjab and Delhi. As of 31 October 2024, India reported the highest number of confirmed chikungunya cases in six years (7), with increases in cases compared to 2023 in multiple states including Maharashtra, Telangana and Delhi, where EWNI cases reported travelling to. 

Table 3. Number of chikungunya cases by country of travel, 2024

Country of travel	Number of cases
India	66
Pakistan	11
Brazil	7
Indonesia	6
Maldives	6
Philippines	5
Bangladesh	3
Nigeria	2
Ghana	1
Kenya	1
Nepal	1
Sri Lanka	1
Not stated	2
Total	112

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. Cases of cholera may be asymptomatic or have mild symptoms, including 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 (8). In 2023, cases were reported in 45 countries worldwide, an increase from 44 in 2022 and 35 in 2021. The disease occurs mainly in Africa and Asia, but sporadic cases have also been reported in other regions (9).

In EWNI, there were 9 cholera cases reported in 2024, all were confirmed. This represents a 36% decrease compared to 2023 where 14 cases were reported. Case numbers were highest in the third and fourth quarters (n=4, n=4) (Figure 4).

Figure 4. Number of cholera cases by quarter, Q1 2020 to Q4 2024

In 2024, 4 cases (44%) were female (aged 41 to 65 years, median=45) and 5 (56%) were male (aged 3 to 52 years, median=33) (Figure 5).

Figure 5. Number of cholera cases by age group and sex, 2024 (n=14)

In 2024, there were 9 cases reported in England, with no cases in Wales and Northern Ireland. The largest proportion of cases were reported in the North West (33%) and the South East (22%) (Table 4).

Table 4. Number of cholera cases in England, Wales and Northern Ireland by geographical distribution, 2024

Geographical area	Number of cases
North West	3
South East	2
East of England	1
Yorkshire and Humber	1
East Midlands	1
London	1
England total	9
Wales	0
Northern Ireland	0
EWNI Total	9

In 2024, travel history was known for all cases, with the majority of these reporting travel to Southern Asia (4 cases, 44%) and Western Africa (4 cases, 44%) (Table 5).The most frequently reported countries of travel were Nigeria (3 cases) and Pakistan (3 cases).

Cholera case numbers have continued to be high in recent years during the 7th global pandemic. In 2024, as of November, cases had been reported in 33 countries across five WHO regions, with the highest number of cases in the Eastern Mediterranean, followed by Africa and South-Est Asia (10).

Table 5. Number of cholera cases by country of travel, 2024

Country of travel	Number of cases
Nigeria	3
Pakistan	3
India	1
Ghana	1
Iraq	1
Total	9

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.

Severe dengue is rare in travellers (11). 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 (11, 12, 13). 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, with significant increases particularly noted in Asia and the Americas (11).

In EWNI, 904 dengue cases were reported in 2024, of which 806 (89%) were confirmed cases and 98 (11%) were probable cases. This represents a 43% increase compared to 2023 (n=631) and marks the highest number of cases reported since dengue surveillance commenced in 2009. The majority of cases were diagnosed in the first and third quarters, with 254 and 270 cases, respectively (Figure 6).

Figure 6. Number of dengue cases by quarter, Q1 2020 to Q4 2024

In 2024, 454 cases (50.2%) were female (aged 0 to 87 years, median=38) and 450 (49.8%) were male (aged 0 to 88, median=41) (Figure 7).

Figure 7. Number of dengue cases by age group and sex, 2023 (n=904)

In 2024, there were 876 cases reported in England, 18 cases in Wales and 10 cases in Northern Ireland. The largest proportion of cases in England were reported in London (38%) (Table 6).

Table 6.  Number of dengue cases in England, Wales and Northern Ireland by geographical distribution, 2024

Geographical area	Number of cases
London	329
South East	175
South West	89
East of England	77
North West	56
Yorkshire and Humber	50
West Midlands	46
East Midlands	41
North East	13
England total	876
Wales	18
Northern Ireland	10
EWNI total	904

In 2024, travel history was known for 824 out of 904 cases (91%) reported in EWNI. Most were linked to travel to Southern Asia (245 cases, 30%) and South-Eastern Asia (204 cases, 25%) (Table 7). India remained the most reported travel destination (179 cases, up 23% compared to the previous year), while Thailand was the highest in South-Eastern Asia (96 cases, up 23% compared to the previous year).

Dengue cases linked to South America and the Caribbean surged by 111% and 257%, respectively, compared to the previous year, aligning with major outbreaks in these regions. Brazil saw the highest increase, with 71 cases – a 407% rise from the previous year (14 cases). Barbados also saw a significant rise in cases, with 132 cases reported (313% increase compared to the previous year). These trends reflect  large increases in dengue seen in the Americas, with over 11 million cases reported in the first half of the year (14).

In 2024, one case in EWNI reported travel to Spain. While autochthonous dengue has been reported sporadically in Europe, France and Italy saw significant outbreaks in 2024, and Spain and Croatia also recorded locally acquired cases (12, 13).

This increase in imported dengue cases reflects a global dengue surge (15). According to the European Centre for Disease Prevention and Control (ECDC), over 14 million cases and more than 10,00 dengue-related deaths were reported worldwide 2024 (16). The rise is driven by climate change, rising temperatures and flooding (17).

Table 7. Number of dengue cases by region of travel, 2024

Country of travel	Number of cases
India	179
Barbados	132
Thailand	96
Indonesia	73
Brazil	71
Mexico	27
Maldives	19
Philippines	18
Nepal	16
Argentina	16
Pakistan	15
Malaysia	15
Singapore	15
Sri Lanka	14
United Arab Emirates	12
Somalia	11
Costa Rica	10
Grenada	10
Trinidad and Tobago	9
Guatemala	8
Other Caribbean	43
Other Central America	13
Other Eastern Africa	16
Western Asia	5
Other South-Eastern Asia	18
Other Southern Asia	6
Middle Africa	6
Other South America	15
Eastern Asia	8
Northern Africa	5
Oceania	6
Western Africa	9
Northern America	4
Southern Europe	1
Not stated	80
Total*	1002

*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.

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 (18, 19, 20).

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 is transmitted to humans through flea faeces mostly in Asia, Africa and the Western Pacific. R. prowazekii is transmitted to humans through louse faeces and is 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 endemic across Asia, the Western Pacific, South America and Africa and cause an estimated 1 million cases per year (19, 20).

In 2024, there were 44 cases of rickettsial infections reported in EWNI, which is the same number of cases reported in 2023. Of these, 20 (45%) were confirmed cases and 24 (55%) were probable cases. Case numbers in 2024 were the highest in quarters 2 and 4 (n=15 and n=12) (Figure 8). Of the reported cases, there were 19 cases (43%) in the spotted fever group, 14 cases (32%) in the typhus group and 11 cases (25%) in the scrub typhus group.

Figure 8. Number of cases with rickettsial infections by quarter, Q1 2020 to Q4 2024

In 2024, age and sex were known for all cases. Of these, 21 cases (48%) were female (aged 12 to 80 years, median=44) and 23 (52%) were male (aged 12 to 75 years, median=51) (Figure 9).

Figure 9. Number of cases with rickettsial infections by age group and sex, 2024 (n=44)

In 2024, there were 42 cases reported in England, one case in Wales and one case in Northern Ireland. The largest proportion of cases in England were reported in London (40%) (Table 8).

Table 8. Number of cases with rickettsial infections in England, Wales and Northern Ireland by geographical distribution, 2024

Geographical area	Number of cases
London	17
South East	7
East Midlands	4
East of England	4
South West	3
North East	3
Yorkshire and Humber	2
North West	1
West Midlands	1
England total	42
Wales	1
Northern Ireland	1
EWNI Total	44

In 2024, travel history was known for 43 out of 44 cases. Of these, the majority of spotted fever cases reported travel to Southern Africa (15 cases, 79%). Scrub typhus cases are tested only when travel to Southern Asia or South-Eastern Asia is reported, and of the cases in 2024, 7 cases (64%) travelled to Southern Asia and 2 cases (18%) travelled to South-Eastern Asia. Typhus group cases reported travel to multiple regions including South-Eastern Asia (6 cases, 43%), Southern Asia (2 cases, 14%) and Northern Africa (2 cases, 14%).

For all cases of rickettsial infection, the most frequently reported country of travel was South Africa (15 cases), followed by India (5 cases) and Indonesia (4 cases) (Table 5).

Table 9. Number of cases with rickettsial infections by region of travel and rickettsial group, 2024

Country of travel	Scrub typhus	Spotted fever	Typhus group	Total number of cases
South Africa	-	15	-	15
India	2	1	2	5
Indonesia	1	-	3	4
Bangladesh	2	-	-	2
Hong Kong	1	-	1	2
Nepal	2	-	-	2
Vietnam	-	-	2	2
Algeria	-	-	1	1
Australia	1	-	-	1
Cambodia	-	-	1	1
Egypt	-	-	1	1
Ethiopia	-	-	1	1
Mauritius	1	-	-	1
Sierra Leone	-	-	1	1
Singapore	1	-	-	1
Spain	-	-	1	1
Sri Lanka	1	-	-	1
Thailand	1	-	-	1
Zimbabwe	-	1	-	1
Africa unspecified	-	1	-	1
Asia unspecified	-	1	-	1
Not stated	-	-	1	1
Total*	13	19	15	47

*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 (21).

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 (22).

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.

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 2024, 90 countries across Africa, Europe, the Americas, South-East Asia and the Western Pacific have reported autochthonous Zika virus disease cases (23).

In 2024, there were 16 Zika virus disease cases reported in EWNI, all were confirmed. This represents a 100% increase compared to 8 cases reported in 2023. Case numbers were highest in the first and third quarters (n=5 and n=6) (Figure 10).

Figure 10. Number of Zika virus disease cases by quarter, Q1 2019 to Q4 2024

In 2024, 10 cases (63%) were female (aged 22 to 54 years, median=38.5) and 6 (37%) were male (aged 26 to 59, median=38.5) (Figure 11).

Figure 11. Number of Zika virus disease cases by age group and sex, 2024 (n=16)

In 2024, there were 15 cases reported in England, one case in Wales and zero cases in Northern Ireland. The largest proportion of cases in England were reported in London (47%) (Table 10).

Table 10. Number of Zika virus disease cases in England, Wales and Northern Ireland by geographical distribution, 2024

Geographical area	Number of cases
London	7
South East	4
Yorkshire and Humber	2
West Midlands	1
North West	1
England Total	15
Wales	1
Northern Ireland	0
EWNI total	16

In 2024, travel history was known for all Zika virus disease cases, with the majority linked to South-Eastern Asia (9 cases, 56%). The most frequently reported country of travel was Thailand (6 cases, 30%), followed by India (4 cases, 20%) (Table 11). Notably, Thailand reported 433 cases across 44 provinces (24), representing a decrease from the 777 cases reported in 2023. In India, 151 Zika virus disease cases were recorded in 2024, with Maharashtra State reporting the highest number (140 cases) – marking the largest outbreak since its first outbreak in 2021 (25).

Three cases were linked to travel to Africa: 2 to Seychelles and 1 to Ghana. This is the first time since 2015 that Zika virus disease cases have been associated with travel to Africa, where previously one case reported travel to Guinea.

Table 11. Number of Zika virus disease cases by country of travel, 2024

Country of travel	Number of cases
Thailand	6
India	4
Seychelles	2
Singapore	2
Indonesia	1
Vietnam	1
Malaysia	1
Philippines	1
Ghana	1
Kenya	1
Total*	20

*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.

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 (26, 27).

In EWNI there were no cases of Japanese encephalitis reported in 2024. The most recently reported case in EWNI 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 (28).

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. 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 (29).

To date there have been no diagnosed cases of Oropouche virus disease in EWNI.

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 (30).

In EWNI there were no cases of yellow fever reported in 2024. The most recently reported case in EWNI was in 2018.

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30. WHO. ‘Yellow fever’ (updated 31 May 2023)