Research and analysis

Enteric fever (typhoid and paratyphoid) England, Wales and Northern Ireland: 2023

Updated 22 August 2024

Applies to England, Northern Ireland and Wales

Enteric fever (also known as typhoid and paratyphoid) is an illness caused by the bacteria Salmonella enterica subspecies enterica serovar Typhi (typhoid) or serovars Paratyphi A, B or C (paratyphoid). Typhoid fever is a serious disease and can be life-threatening unless treated promptly with antibiotics. The disease may last several weeks, and convalescence takes some time. In the literature, paratyphoid is considered to be typically milder than typhoid and of shorter duration (1,2).

The bacteria that cause typhoid and paratyphoid only occur in humans. Humans acquire infection through eating food or drinking water that has been contaminated with infected faeces or through direct faecal-oral transmission. Transmission occurs following the ingestion of food or water that has been heavily contaminated (10 or more organisms may be required to cause illness) by the bacterium S. Typhi or S. Paratyphi. In the UK, most cases of typhoid and paratyphoid are acquired abroad in countries and regions of the world where hygiene or sanitation is poor.

This report summarises the epidemiology of laboratory-confirmed symptomatic cases of S. Typhi and S. Paratyphi reported in England, Wales and Northern Ireland (EWNI) in 2023. It includes both reference laboratory and enhanced enteric fever surveillance data. Additional summaries of asymptomatic, probable and possible cases for England are presented at the end of this report.

Case definitions

Typhoid and paratyphoid case definitions (3).

Confirmed case

A confirmed case is defined as an individual who has S. Typhi or S. Paratyphi infection confirmed by the UKHSA (UK Health Security Agency) Gastrointestinal Bacteria Reference Unit (GBRU) Salmonella Reference Service (SRS) ^{[footnote 1]}.

Probable case

A probable case is defined as an individual who either:

• has a local laboratory presumptive (locally confirmed) identification of Salmonella Typhi (S. Typhi) or S. Paratyphi on faecal and/or blood culture, or culture of another sterile site (for example, urine), with or without clinical history compatible with typhoid/paratyphoid
• is a returning traveller giving a clinical history compatible with typhoid/paratyphoid and documentation of a positive blood/faecal culture (or positive PCR for S. Typhi / S. Paratyphi on blood)

Possible case

A possible case is defined as an individual who either:

• has a clinical history compatible with typhoid/paratyphoid and where the clinician suspects typhoid/paratyphoid is the most likely diagnosis
• has a clinical history of fever and malaise and/or gastrointestinal symptoms compatible with typhoid/paratyphoid and an epidemiological link such as contact with a case or a source of typhoid/paratyphoid, for example, from ‘warn and inform’ information
• is a returning traveller reporting a diagnosis made abroad with salmonella PCR from faeces but no documented evidence of a positive blood or faecal culture for typhoid or paratyphoid

Data sources

Confirmed symptomatic cases of S. Typhi and S. Paratyphi in England, Wales and Northern Ireland are diagnosed by the UKHSA Salmonella Reference Service (SRS), within the Gastrointestinal Bacteria Reference Unit (GBRU). Data for laboratory-confirmed cases from 2007 onwards were extracted from the reference laboratory database using the ‘date received by the laboratory’.

All S. Typhi and S. Paratyphi isolates referred to the SRS undergo identification using whole genome sequencing (WGS) and single nucleotide polymorphism (SNP) typing (4, 5).

Cases are occasionally tested multiple times for confirmation and to check the infection has cleared, therefore data has been deduplicated so that only one laboratory report for each case is counted.

Epidemiological information was obtained from enhanced enteric fever surveillance (6). For England cases, additional details were sourced from the UKHSA case management system (HPZone) while Wales and Northern Ireland provided surveillance information directly for their respective cases.

All data was analysed using Excel for Office 365 (Version 2208, Microsoft).

General trend

Data on travel to and from the UK, obtained from the ONS International Passenger Survey, represents the most up to date travel data currently available.

In 2023, UK residents made 86.2 million visits abroad, a significant increase compared to 2022 (71.0 million) (7). There were 38.0 million visits made by overseas residents to the UK, compared to 31.2 million in the previous year 2022. In comparison, 2019 saw 93.1 million visits abroad by UK residents and 40.9 million visits to the UK by overseas residents, indication that travel trends in 2023 have nearly returned to pre-pandemic levels.  

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). The top 5 most visited countries were Spain, France, Italy, Greece and Portugal (7).

Holiday travel was also the most popular reason for overseas residents visiting the UK in 2023, with 15.9 million visits, followed by visiting friends and relatives (12.8 million) and business travel (6.5 million) (7). Residents of the USA, France, Germany, Republic of Ireland and Spain represented the highest numbers of overseas residents visiting the UK.

In 2023, 645 laboratory-confirmed symptomatic cases of S. Typhi and S. Paratyphi infection were reported by the UKHSA SRS in EWNI, the highest annual case number reported since 1980 (8-10). This represents a significant increase of 37% compared to the 470 cases reported in 2022 (see Table 1 and Figure 1). Of these, 63% were caused by S. Typhi, 32% of cases by S. Paratyphi A and 4% by S. Paratyphi B (see Table 1). There were 7 additional cases of mixed infection (cases co-infected with both S. Typhi and S. Paratyphi). No cases of S. Paratyphi C were reported in 2023.

Table 1. Laboratory-confirmed symptomatic cases of enteric fever, England, Wales and Northern Ireland by organism: 2014 to 2023

Year	S. Typhi	S. Paratyphi A	S. Paratyphi B	S. Paratyphi C	Mixed infection	Total	% S. Typhi
2014	185	113	10	1	1	310	60%
2015	168	108	26	-	-	302	56%
2016	172	133	8	-	-	313	55%
2017	187	103	15	-	-	305	61%
2018	205	126	19	-	-	350	59%
2019	321	166	19	1	-	507	63%
2020	127	57	6	-	-	190	67%
2021	108	31	13	-	-	152	71%
2022	313	135	18	-	4	470	67%
2023	405	204	29	-	7	645	63%

Figure 1. Laboratory-confirmed symptomatic cases of S. Typhi and S. Paratyphi, with % change year to year, England, Wales and Northern Ireland: 2014 to 2023

Age and sex

In 2023, both age and sex were known for all 645 laboratory-confirmed symptomatic cases; 42% were adults between 20 and 39 years (see Figure 2) and the median age was 25 years (range 1 to 77 years). Those under 15 years accounted for 28% of cases, with 1% (4 cases) of the total in children under 2 years (and thus not routinely eligible for vaccination). Overall, there were slightly more male (56%) than female cases.

Figure 2. Laboratory-confirmed symptomatic cases of enteric fever, England, Wales and Northern Ireland by age and sex where sex is known: 2023 (total 645 cases)

Geographical distribution

Geographical areas were assigned based on patient postcode; in a small number of cases patient postcode was missing and the sending laboratory postcode was used. In 2023, the largest proportion of cases of S. Typhi and S. Paratyphi in England were reported in London (29%), a decrease compared to the previous year (34% in 2022) (see Table 2). All regions across England and Wales saw an increase in cases compared to the previous year. The largest increases were seen in the South West region and Wales.

Table 2. Laboratory-confirmed symptomatic cases of S. Typhi and S. Paratyphi, England, Wales and Northern Ireland by geographical distribution: 2022 and 2023

Geographical area UKHSA	2022	2023	% change
London	160	185	16%
West Midlands	63	95	51%
North West	50	82	64%
South East	55	60	9%
East of England	35	60	71%
Yorkshire and Humber	38	55	45%
East Midlands	35	50	43%
South West	11	25	127%
North East	12	16	33%
England Total	459	628	37%
Wales	8	15	88%
Northern Ireland	3	2	-33%
EWNI Total	470	645	37%

Disease presentation and outcomes

In 2023, symptom information was known for 99% (640 out of 645) of laboratory-confirmed symptomatic cases of enteric fever. Hospital admission data was available for 643 cases, with 556 (86%) requiring hospitalisation due to their illness. Additionally, where data was available, 66% (379 out of 571) cases reported absence from work or school as a result of their illness. 

The most common symptom for all cases combined was fever, with 92% of S. Typhi and S. Paratyphi A cases, 93% of S. Paratyphi cases, and was reported in all cases of mixed infections. Diarrhoea was the second most frequent symptom, present in 67% in S. Typhi cases, 60% in S. Paratyphi A cases, 86% in S. Paratyphi cases, and 71% in mixed infection cases. Vomiting and headache were also frequently reported symptoms. Vomiting was noted in 48% of S. Typhi cases, while headache was a significant symptom in 52% of S. Paratyphi A cases and 66% of mixed infections. Notably, rigors were reported in 86% of mixed infection cases.

A high proportion of cases across all infections required hospitalisation as a result of their illness, with 87% of S. Typhi, 84% of S. Paratyphi A, 72% of S. Paratyphi B, and all mixed infection cases requiring medical care.

Where data was available, 60% of S. Typhi cases, 57% of S. Paratyphi A cases, 45% of Paratyphi B cases, and 57% of mixed infection cases reported missing work or school as a consequence of their illness.

Travel history

In 2023, 99.8% (644 out of 645) of laboratory-confirmed symptomatic cases of S. Typhi and S. Paratyphi had travel history information recorded (that is, whether they had travelled abroad or not)(see Figure 3). Of these, 97% (622 out of 644) reported onset of illness within 28-days of travel to an endemic region of the world (and therefore were presumed to have acquired the infection abroad) (see Figure 4). This represents an increase from 96% in 2022. Of cases in 2023, 88% (567 out of 622) were UK residents who had travelled abroad from EWNI, while the remainder were either new entrants (49 cases, 8%) or foreign visitors (6 cases, 1%) to EWNI. For 22 cases no foreign travel was reported in the 28 days prior to becoming symptomatic was reported.

Figure 3. Laboratory-confirmed symptomatic cases of enteric fever, England, Wales and Northern Ireland by travel history: 2014 to 2023

Figure 4. Presumed country of infection for laboratory-confirmed symptomatic cases of enteric fever that travelled abroad from England, Wales and Northern Ireland: 2023 (total 567 cases)

Where reason for travel was documented (546 cases), 87% of cases travelled abroad from EWNI to visit friends and relatives (VFR) (477 out of 546) (see Figure 5). The majority travelled to countries in Southern Asia (see Table 3) and acquired the infection while visiting friends or relatives abroad in Pakistan and India.

Ethnicity was not known for 51 cases that travelled abroad to visit friends and relatives, these individuals travelled to India (24), Pakistan (20), Bangladesh (5), Afghanistan (one) and Zimbabwe (one).

For those UK resident cases who did not visit friends and relatives (69 cases), where reason for travel was known the reasons provided included holidays (60), business (3) and other, such as studying abroad (6). These cases travelled to a number of countries, including India (25), Pakistan (16), and countries in the Americas (20), Asia (12), Africa (2) and Oceania (one), with some cases travelling to more than one country.
For the 21 cases where reason for travel was not stated, eleven travelled to India, 6 to Pakistan, 2 to Saudi Arabia (with one of these cases also travelling to Cyprus), one to Ghana and one to Iraq.

Figure 5. Reason for travel for laboratory-confirmed symptomatic cases of enteric fever that travelled abroad from England, Wales and Northern Ireland: 2023 (total 567 cases)

Table 3. Country of travel and ethnicity for laboratory-confirmed symptomatic cases of enteric fever that travelled abroad from England, Wales and Northern Ireland to visit friends and relatives: 2023 (a total 477 cases, see note 1)

Presumed country of infection	Pakistani	Indian	Bangladeshi	Asian other	Black African	White British	Other/ mixed	Not stated	Total
Pakistan	213	2	-	4	-	2	8	20	249
India	2	146	1	-	-	-	5	24	178
Bangladesh	-	-	26	-	-	-	1	5	32
Other Asia	6	-	1	5	-	1	6	1	21
Africa	-	-	-	-	6	-	-	1	7
Grand Total	221	148	28	9	6	3	19	51	484

Note 1: some cases travelled to more than one country; all countries are included here so the totals will be higher than the actual number of cases

Clusters

Whole genome sequencing, carried out for all S. Typhi and S. Paratyphi cases, identifies clusters based on single nucleotide polymorphisms (SNPs). Those described here are 5-SNP clusters, which indicate closely genetically linked organisms. Due to the low mutation rate of typhoidal salmonella and the recognition of specific clones circulating endemic countries, strains within the same 5 SNP cluster can indicate potential source of travel (11).

S. Typhi

In 2023, a total of 43 clusters of S. Typhi were identified.  The largest of these, cluster t5.1, consisted of 108 cases, accounting for 26% (108 out of 412) of all laboratory-confirmed symptomatic cases of S. Typhi. Within this cluster, 87% (94 cases) reported travel to Pakistan, mainly to Karachi and Lahore. In addition, 46 cases in this cluster were linked to an ongoing outbreak of an extensively drug-resistant (XDR) strain of S. Typhi first identified in 2016 in Sindh province, Pakistan. This represents an increase from the 41 cases reported in the previous year, continuing the trend seen before the COVID-19 pandemic of an increasing number of imported XDR S. Typhi cases within this cluster (11, 12). This strain is resistant to most antibiotics used to treat enteric fever, including ampicillin, chloramphenicol, co-trimoxazole (which confers multidrug-resistant (MDR) S. Typhi), fluoroquinolones and third generation cephalosporins (bla CTX-M-15 extended spectrum beta-lactamase (ESBL) producers)(12, 13). Since 2019, the XDR strain has been found circulating in other areas of Pakistan and is no longer restricted to the Sindh province (13, 14). In 2023, the majority of the XDR S. Typhi cases within this cluster had travel history to Pakistan (42 cases), while three cases travelled to Afghanistan. The remaining case had no travel history outside EWNI, and no potential source of infection was identified. See clinical guidance for the management of these extensively drug-resistant cases.

The second largest cluster of S. Typhi, t5.786, consisted of 34 cases reported in 2023. This cluster was first identified in 2020 with 37 cases in total, all with history of travel to Pakistan.

S. Paratyphi A

For S. Paratyphi A, 21 clusters were identified in 2023. The largest cluster, t5.49, consisting of 37 cases, and has had 89 cases since it was first identified in 2014. The majority of cases travelled to Pakistan (86 cases). One case travelled to India in 2023, and one case to Saudi Arabia and one case did not travel in 2019.
The second largest cluster in 2023, t5.40, consisted of 27 cases. This cluster was first identified in 2015 and has 39 cases overall, all with history of travel to India.

S. Paratyphi B

For S. Paratyphi B, 4 clusters were identified in 2023. The largest, t5.141, had 9 cases all with a travel history to Iraq. This cluster was first identified in 2015 (15) with 30 cases in total, mainly associated with travel to Iraq (27 cases). The remaining two cases travelled to Kazakhstan (one) and Kyrgyzstan (one) in 2022. 

The second largest S. Paratyphi B cluster in 2023, t5.129, consisted of 7 cases, all who travelled to South America, with the majority to Bolivia (5 cases). This cluster was first identified in 2015 and is mainly linked with travel to South America, particularly to Bolivia (18 out of 28 cases). One case in 2015 and 3 cases in 2018 had no travel history reported, while one case reported travel to Costa Rica in 2022.

Non-travel-associated cases

In 2023, there were 22 cases classified as non-travel-associated cases, these were confirmed cases of symptomatic enteric fever where the case reported that they did not travel in the 28 days prior to becoming symptomatic: 18 were caused by S. Typhi and 4 were caused S. Paratyphi A.

S. Typhi

Of the 18 non-travel-associated cases caused by S. Typhi:

• Four cases had household contacts who had recently returned from an endemic country. One of these cases was identified as part of a 5-SNP cluster linked to cases with travel history to India and Pakistan, first identified in 2014
• Two cases had been in contact with a family member or a friend who had recently returned from an endemic country. One of these cases was part a 5-SNP cluster first identified in 2018, mainly associated with travel to Pakistan
• One case had been in recent contact with their partner, a possible carrier with no recent travel, identified as a potential source of infection. A possible carrier is defined as a person with no recent history of travel or a relevant medical history but who may have lived in or travelled extensively to endemic regions (6)
• One case was confirmed as a laboratory-acquired infection after WGS results confirmed a sequencing match with a sample the case had been testing
• No potential sources of infection were identified for the remaining 10 cases

S. Paratyphi A

Of the 4 non-travel-associated cases caused by S. Paratyphi A:

• Two cases had been in contact with a family member or a friend who had recently returned from an endemic country. Both were part of two separate 5-SNP clusters: one linked to travel to Pakistan and first identified in 2015, and the other linked to travel to India, also first identified in 2015
• No potential sources of infection were identified for the remaining two cases

Confirmed asymptomatic cases

In 2023, there were 3 confirmed asymptomatic cases of enteric fever caused by S. Typhi (2 cases) and S. Paratyphi A (one case). Two cases were identified through contact tracing as household contacts and co-travellers of known symptomatic cases; one travelled to India and was part of a 5-SNP cluster, while the other case travelled to Bangladesh. The remaining case, a non-travel-associated case, was identified during contact screening as a household contact of a confirmed symptomatic case, also non-travel associated; both were part of the same 5-SNP cluster. No potential sources of infection were identified for this case.

Probable and possible cases

In 2023, there were 10 probable and 18 possible cases of enteric fever as defined in the Public Health Operational Guidelines for Enteric Fever (6). Of these, 25 travelled abroad from EWNI and two cases did not travel abroad. Travel history information for the probable and possible cases is detailed in (see Table 5). Caution should be used when interpreting this data as it has not been confirmed by the UKHSA reference laboratory.

Table 4. Country of travel and reason for travel for probable and possible cases of enteric fever that travelled abroad from England, Wales and Northern Ireland: 2023 (a total of 26 cases, see note 1)

World region of travel	VFR	Holiday	Business	Other	Total
India	6	1	-	-	7
Bangladesh	3	1	-	-	4
Pakistan	3	-	-	-	3
Indonesia	1	3	-	-	4
Thailand	2	-	-	-	2
Uganda	2	-	-	-	2
Cambodia	1	-	-	-	1
Côte d’Ivoire	1	-	-	-	1
Nepal	1	-	-	-	1
Sierra Leone	-	-	1	-	1
Turkey	-	1	-	-	1
Vietnam	1	-	-	-	1
Zambia	-	-	-	1	1
Total	21	6	1	1	29

Information resources

• NaTHNaC typhoid and paratyphoid fact sheet
• NaTHNaC food and water hygiene advice

• UKHSA typhoid and paratyphoid page

• Typhoid: health advice for travellers (Asian languages)
• Travelling overseas to visit friends and relatives − health advice
• Gastrointestinal bacteria reference unit − reference and diagnostic services

References

1. Cook GC and Zumla A. ‘Manson’s tropical diseases’ Elsevier Health Sciences 2009
2. Heymann DL. ‘Control of communicable diseases manual’ American Public Health Association 2008
3. UK Health Security Agency. Public health operational guidelines for typhoid and paratyphoid (enteric fever)
4. Chattaway MA and others. ‘The Transformation of Reference Microbiology Methods and Surveillance for Salmonella With the Use of Whole Genome Sequencing in England and Wales’ Frontiers in Public Health 2019, volume 7, page 317. doi: 10.3389/fpubh.2019.00317
5. Dallman, TJ and other. ‘SnapperDB: A database solution for routine sequencing analysis of bacterial isolates’ bioRxiv 189118, doi: https://doi.org/10.1101/189118
6. UK Health Security Agency. Typhoid and paratyphoid: guidance, data and analysis. Health Protection Collection (online)
7. Office for National Statistics. ‘Travel trends: 2023’
8. Health Protection Agency. ‘Salmonella Typhi and Salmonella Paratyphi. Laboratory reports (cases only). England and Wales, 1980 - 2005’
9. Public Health England. ‘Typhoid and paratyphoid: laboratory confirmed cases in England, Wales and Northern Ireland’
10. UK Health Security Agency. ‘Typhoid and paratyphoid: laboratory confirmed cases in England, Wales and Northern Ireland’
11. Chattaway MA, and others. ‘Phylogenomics and antimicrobial resistance of Salmonella Typhi and Paratyphi A, B and C in England, 2016-2019’ Microbial Genomics 2021, volume 7, issue 8, 000633.
12. Nair S, and others. ‘ESBL-producing strains isolated from imported cases of enteric fever in England and Wales reveal multiple chromosomal integrations of blaCTX-M-15 in XDR Salmonella Typhi’. Journal of Antimicrobial Chemotherapy 2021, volume 76, issue 6, pages 1459-1466.
13. World Health Organisation Disease Outbreak News Item. ‘Typhoid fever - Islamic Republic of Pakistan’
14. Rasheed F and others. ‘Emergence of Resistance to Fluoroquinolones and Third-Generation Cephalosporins in Salmonella Typhi in Lahore, Pakistan’ Microorganisms 2020, volume 8, page 1336. doi: https://doi.org/10.3390/microorganisms8091336
15. Chattaway MA and others. ‘Genomic sentinel surveillance: Salmonella Paratyphi B outbreak in travellers coinciding with a mass gathering in Iraq’ Microbial Genomics 2023, volume 9. doi: 10.1099/mgen.0.000940

1. As we only collect data from the UKHSA Salmonella Reference Service, local reports of cases of enteric fever may differ for Wales and Northern Ireland. ↩