Research and analysis

Malaria imported into the UK: 2022

Updated 3 December 2024

Introduction

Malaria is a serious and potentially life-threatening febrile illness caused by infection with protozoan parasites of the genus Plasmodium. It is transmitted to humans by the bite of the female Anopheles mosquito in tropical and subtropical regions of the world. There are 5 species of Plasmodium that infect humans: P. falciparum (responsible for the most severe form of malaria and the most deaths), P. vivax, P. ovale, P. malariae and P. knowlesi.

Malaria is not currently transmitted in the UK, but travel-associated cases occur in those who have returned to or arrived in the UK from malaria-endemic areas. Where there is no clear history of recent travel to a malaria-endemic area, these cases are classified as cryptic, or non-travel cases and are very uncommon in the UK.

More information about malaria is available on the Malaria: guidance, data and analysis web page.

Methodology

This report presents data on malaria imported into the United Kingdom (UK) in 2023, mostly based on figures reported to the UK Health Security Agency (UKHSA) Malaria Reference Laboratory (MRL), Public Health Scotland and the International Passenger Survey (IPS) data provided to the Travel Health team by the Office of National Statistics (ONS).

The MRL data set is the most complete source of information about malaria available in the UK, and one of the most complete internationally. A capture-recapture study estimated that the MRL surveillance system captured 56% of cases in England (66% for Plasmodium falciparum and 62% for London cases) (1). The MRL relies on information supplied by the notifying laboratory, medical personnel, or coroner, and where this information is not known or not supplied, some of the epidemiological information is incomplete. Where a malaria-associated death is notified, further detailed information is requested as part of a national audit into deaths from imported malaria. Malaria surveillance data is used to inform the UK malaria prevention strategy (3) so it is essential that the data collected is as complete as possible.

Malaria is a notifiable disease in the UK and clinical and laboratory staff are obligated under law to notify cases to their proper officer (4). However, in 2022, only 15% of malaria cases reported to MRL were officially notified (5). Clinical and laboratory staff are therefore reminded of the requirement to notify cases to the designated local public health authority and to report all clinical and epidemiological detail to the MRL using the Malaria: risk assessment form.

Data analysis for this report was conducted by the UKHSA Travel Health and IHR team and colleagues at the MRL have reviewed and agreed the report. For the purpose of the analysis, the United Nations (UN) regions were used to assign region of travel and each region was assigned based on the stated country of travel (6).

General trend

In 2022, 1,555 cases of imported malaria were reported in the UK (1,476 in England, 54 in Scotland, 19 in Wales and 6 in Northern Ireland). This is 54% higher than numbers reported in 2021 (1,012 cases) and 7.8% above the mean number of 1,433 cases reported annually between 2013 and 2022. Two deaths were reported in 2022, which is lower than the annual average of 10 deaths between 2013 and 2022.

Figure 1. Cases of malaria in the UK: 2003 to 2022

In the 10 years between 2013 and 2022, the total number of malaria cases reported in the UK each year has fluctuated around a mean of 1,433 (95% CI: 1,186 to 1,700), which is slightly higher than the mean for 2012 to 2021 (1,425, 95% CI: 1,165 to 1,686), but lower than the mean for 2010 to 2019 (1,612, 95% CI: 1,508 to 1,715) which shows that the mean is slowly returning back to pre-pandemic levels.

The great majority of malaria cases diagnosed in the UK in 2022 were caused by P. falciparum, which is consistent with previous years and reflects the global epidemiology of malaria. The total proportion of cases caused by P. falciparum, P. vivax and P. ovale slightly decreased in 2022 compared to 2021 and the total proportion of cases caused by P. malariae and mixed infections showed an increase in 2022. The number of cases caused by P. knowlesi remained at zero in 2022 (Table 1).

Malaria caused by P. falciparum is of the most public health interest because, as well as accounting for the most cases, it also causes the most serious disease. Although P. ovale accounts for a slightly higher proportion of cases than P. vivax, P. vivax is of greater interest as it can have more serious disease implications. Of the parasites that cause malaria, P. falciparum is the most prevalent species in Africa and P. vivax is the dominant species in most other countries (7).

Table 1. Malaria cases in the UK by species: 2021 and 2022

Malaria parasite	Cases (% of total): 2022	Cases (% of total): 2021
P. falciparum	1,320 (84.9%)	868 (85.8%)
P. vivax	70 (4.5%)	50 (4.9%)
P. ovale	104 (6.7%)	66 (6.5%)
P. malariae	47 (3.0%)	26 (2.6%)
Mixed infection	14 (0.9%)	2 (0.2%)
P. knowlesi	0 (0.0%)	0 (0.0%)
Total	1,555	1,012

Age and sex

Age and sex were known for 1,532 out of 1,555 cases (99%) and the majority of cases were male, consistent with previous years. In 2022, 972 cases (63%) were male (aged one to 86 years, median=42) and 560 cases (36%) were female (aged one to 81 years, median=39). During the period from 2000 to 2022, the median age of those who died from falciparum malaria was 52 years. UKHSA MRL data over 27 years demonstrates that older age is consistently a major risk factor for death from falciparum malaria and severe vivax malaria (8, 9).

Figure 2. Cases of malaria in the UK by age group and sex: 2022 (n=1,532)  

Geographical distribution

Consistent with previous years, London reported the largest proportion of malaria cases in the UK in 2022, accounting for almost half of all UK cases (49%, 758 out of 1,555). The majority of UKHSA regions saw an increase in cases in 2022 compared to 2021, ranging from a relatively small increase of 12% in the Yorkshire and Humber region compared to case numbers doubling in the West Midlands. Wales and Northern Ireland both had decreases in case numbers compared to 2021 with a decrease of 10% in Wales and 25% in Northern Ireland. (Table 2).

Table 2. Cases of malaria in the United Kingdom by geographical distribution, 2022 and 2021

Geographical area (UKHSA Centre)	2022	2021	% change
London	758	498	52%
West Midlands	142	71	100%
East of England	123	91	35%
South East	116	92	26%
North West	154	75	105%
Yorkshire and Humber	58	52	12%
South West	50	30	67%
East Midlands	41	27	52%
North East	34	18	89%
England total	1,476	954	55%
Scotland	54	29	86%
Wales	19	21	-10%
Northern Ireland	6	8	-25%
UK total	1,555	1,012	54%

Travel history and ethnic origin

In 2022, for the cases that had reported a reason for travel (1,072 out of 1,555, 81%), the majority were UK residents travelling abroad (816 out of 1,267, 64%) (see Figure 3). Of the remaining cases where travel status was known, 11% (136 out of 1,267) were new entrants to the UK (also includes foreign students), 3% (37 out of 1,267) were foreign visitors to the UK, 1% (18 out of 1,267) were UK citizens living abroad who travelled to the UK and 5% (65 out of 1,267) were categorised as having other reasons for travel.

Of the cases in UK residents who travelled abroad, reasons for travel were known for all cases (see Figure 4) and include:

• visiting friends and relatives (VFR) – 626 out of 816 (77%)
• travel for holiday – 133 out of 816 (16%)
• business or professional (including armed forces and civilian sea/air crew) – 57 out of 816 (7%)

Figure 3. Travel history and reasons for travel in malaria cases in the UK: 2013 to 2022

Figure 4. Reason for travel for malaria cases that travelled abroad from the UK: 2022 (n= 816)

Country or region of birth for cases that travelled abroad from the UK

Country or region of birth information was known for 566 (69%) of 816 cases that travelled abroad from the UK, of which over three-quarters (432, 76%) were born in Africa, 106 cases (19%) were born in the UK, 12 cases (2%) were born in non-UK Europe, 8 cases (1%) were born in Southern Asia and 8 cases (1%) in other regions. The breakdown of region of birth for malaria cases that have travelled abroad from the UK is shown in (see Figure 5).

Figure 5. Region of birth for malaria cases who travelled abroad from UK: 2022 (n=566)

Table 3. Malaria cases who travelled abroad from the UK by region of birth and proportion of VFR travellers: 2022 (n=566)

Region of birth	N [note 1]	VFR	% VFR
Africa	432	373	86%
UK	106	57	54%
Southern Asia	8	5	63%
Other (includes non-UK Europe)	20	12	60%

Note 1: N is the number of cases where region of birth and reason for travel was known.

Ethnicity of cases that travelled abroad from the UK

Of the malaria cases that travelled abroad from the UK, (where ethnicity was known) more than 4 out of 5 were of black African ethnicity and/or of African descent (82%, 626 out of 765). Of the remaining cases, 32 (4%) were white British, 12 (2%) were Indian, Pakistani, Bangladeshi or of Indian subcontinent (ISC) descent, and 95 (12%) were of other or mixed ethnicity. For this analysis, the Indian subcontinent comprises Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan and Sri Lanka. The breakdown of ethnicity for malaria cases that have travelled abroad is shown in Figure 6.

For non-white British cases that travelled abroad from the UK, 585 out of 733 (80%) were visiting friends or relatives. For white British cases that travelled abroad from the UK, one out of 32 (3%) travelled to visit friends or relatives.

Figure 6. Ethnicity for malaria cases that travelled abroad from the UK: 2022 (n=765)

Country or region of travel for cases that travelled from the UK

Data on travel to and from the UK was obtained from the Office for National Statistics (ONS) International Passenger Survey (IPS).

In 2022 UK residents made 71.0 million visits abroad, this compares with total visits of 19.1 million in 2021. The number of visits in 2022 was 24% less than the peak in 2019, when there were 93.1 million visits. There were 31.2 million visits made by overseas residents to the UK in 2022, which were higher than 2021, where 6.4 million visits were made (10).

In line with increasing numbers of travellers arriving in the UK, the number of malaria infections diagnosed in the UK also increased in 2022 compared with 2021.

Travel by UK residents from the UK for a holiday was the most popular reason for travelling abroad in 2022 with 45.6 million holidays trips made, 22% less than in 2019. In comparison, travel by VFR travellers reduced by 19% compared to 2019 (19 million visits) and there were 4.8 million business trips, 46% less than 2019. A large majority of malaria cases who travelled abroad from the UK were VFR travellers, however the proportion was slightly lower when compared to previous years (77% in 2022 compared with, 87% in 2021, 88% in 2020 and 84% in 2019).

Table 4 shows the breakdown of malaria cases reported by region of travel and parasite species, and the top 20 countries of travel are shown in Table 5. Countries of travel for malaria cases reported in 2022 by count of cases are shown on a map in Figure 7. The majority of cases (where travel history was known) continue to be acquired in Africa, particularly Western Africa where 67% were acquired (548 out of 820), 12% in Middle Africa (102 out of 820) and 12% in Eastern Africa (100 out of 820) in 2022. These numbers reflect in general the global incidence of malaria infection. In 2022, 29 countries accounted for 95% of malaria cases globally, and 4 countries accounted for almost half of all cases globally (11):

• Nigeria (27%)
• the Democratic Republic of the Congo (12%)
• Uganda (5%)
• Mozambique (4%)

Table 4. Cases of malaria that travelled abroad from the UK by species and region of travel: 2022 and 2021

Region of travel	P. falciparum	P. vivax	P. ovale	P. malariae	Mixed	2022 total	2021 total
Western Africa	503	-	24	16	5	548	491
Middle Africa	91	-	5	4	2	102	61
Eastern Africa	94	1	1	3	1	100	38
Northern Africa	21	7	1	1	-	30	12
Southern Asia	3	14	-	-	-	17	14
Africa unspecified	1	-	1	1	-	3	3
South America	1	1	-	-	-	2	-
Southern Africa	-	-	1	-	-	1	2
Western Asia	-	-	-	1	-	1	1
South-Eastern Asia	-	-	-	1	-	1	-
Not stated	12	1	2	-	-	15	10
Total [note 2]	726	24	35	27	8	820	632

Note 2: Some cases travelled to more than one region; all regions are included here so the total may be higher than the actual number of cases.

Table 5. Cases of malaria that travelled abroad from the UK by Plasmodium species and top 20 countries of travel: 2022 and 2021

Country of travel	P. falciparum	P. vivax	P. ovale	P. malariae	Mixed	2022 Total	2021 Total
Nigeria	230	-	13	10	3	256	286
Sierra Leone	114	-	8	3	2	127	54
Ghana	84	-	1	4	-	89	65
Uganda	54	-	-	-	1	55	19
Cameroon	42	-	3	2	-	47	37
Cote d’Ivoire	39	-	1	-	-	40	41
Congo	32	-	-	2	1	35	11
Sudan	19	7	1	1	-	28	12
Kenya	17	-	-	2	-	19	5
Guinea	16	-	1	-	-	17	9
Pakistan	-	9	-	-	-	9	3
Democratic Republic of the Congo	5	-	2	-	1	8	6
Tanzania	7	-	-	-	-	7	3
Senegal	7	-	-	-	-	7	-
South Sudan	6	-	-	-	-	6	3
Zambia	5	-	1	-	-	6	4
Gambia	6	-	-	-	-	6	6
India	3	3	-	-	-	6	8
Angola	4	-	-	-	-	4	3
Gabon	4	-	-	-	-	4	1
Other Eastern Africa	10	1	1	2	-	14	4
Other Western Africa	11	-	-	-	-	11	30
Other Middle Africa	4	-	-	-	-	4	3
Northern Africa	2	-	1	2	-	5	-
Africa unspecified	1	-	1	1	-	3	3
South America	1	1	-	-	-	2	-
Other Southern Asia	-	2	-	-	-	2	3
South-Eastern Asia	-	-	-	1	-	1	-
Southern Africa	-	-	1	-	-	1	2
Western Asia	-	-	-	2	-	2	1
Not stated	14	1	2	-	-	17	10
Total [note 3]	737	24	37	32	8	838	632

Note 3: Some cases travelled to more than one region; all regions are included here so the total may be higher than the actual number of cases.

Figure 7. Countries of travel for cases of malaria that travelled abroad from the UK by count of cases, 2022

Death from malaria

Two deaths were reported in malaria cases in the UK in 2022, which is lower than the annual average of 10 deaths between 2013 and 2022.

Both cases were diagnosed with falciparum malaria, one was female, and one was male. One case was of black African ethnicity, and one was of mixed ethnicity. UK geographical region was known for both cases, and they resided in Yorkshire and Humber and East of England. Both cases travelled abroad from the UK to visit family and relatives and history of prophylaxis information states that in both cases no prophylaxis was taken. 

Of note, there were 2 additional deaths from malaria in individuals who died prior to confirmation by the MRL and who were diagnosed locally. Furthermore, one case who was diagnosed with malaria in 2021 and included as a case in the Malaria imported into the UK: 2021 report, died in 2022.

Prevention and treatment

Chemoprophylaxis

Among malaria cases that travelled abroad from the UK, where the history of chemoprophylaxis (antimalarial medication to prevent infection) was known, 531 out of 613 (87%) had not taken chemoprophylaxis. This proportion is similar to recent years.

Of those who had taken some form of chemoprophylaxis (82 cases, 14%), the choice of drug was stated in 74 (90%) cases, and 63 cases (77%) had taken a drug that was recommended to UK travellers for their destination by the UK Malaria Expert Advisory Group (UKMEAG), formerly the Advisory Committee on Malaria Prevention. This represents 10% (63 out of 613) of the total cases where chemoprophylaxis information was available in 2022. The proportion of the total cases with chemoprophylaxis information that took a drug recommended by the UKMEAG has remained between 9% and 16% between 2000 and 2021, and therefore this is one of the lowest proportions of cases in 22 years. Of the 63 cases that took a drug recommended to UK travellers, whether they had taken it regularly was not stated for all but two case, one case reported that they did not take chemoprophylaxis regularly and the other reported that they did take chemoprophylaxis regularly. Data on adherence to prophylaxis is subject to recall bias and this should be taken into consideration when interpreting this data. When taken correctly, the agents recommended for prophylaxis against falciparum malaria (atovaquone-proguanil, doxycycline and mefloquine) are more than 90% effective (3).

Among malaria cases that travelled abroad from the UK, where the history of chemoprophylaxis was known, a similar proportion of males and females had taken some form of chemoprophylaxis: 14% of females (30 out of 219 cases) and 13% of males (52 out of 394 cases). The median age of cases who had taken some form of chemoprophylaxis (and had travelled abroad from the UK) was 49 years, compared with a median age of 44 years for all cases that had travelled abroad.

Health messages about the importance of antimalarial chemoprophylaxis need to be made more accessible and relevant to groups who are at particular risk of acquiring malaria. The groups at particular risk of not using chemoprophylaxis include those who are visiting family in their country of origin, particularly those of black African heritage and/or those who were born in Africa.

There are several studies that have investigated the reasons for this heightened risk, which could include (12):

• not seeking or not being able to access medical advice on malaria prevention before they travel
• not receiving accurate advice
• not adhering to recommendations on chemoprophylaxis
• not perceiving themselves to be at risk of acquiring malaria (they may have been born in or lived in a malaria-endemic area for many years), or the risk of severe disease following malaria acquisition
• cost of chemoprophylaxis

The burden of falciparum malaria in particular falls heavily on those of black African heritage, and this group is important to target for pre-travel advice.

Taking fever seriously on return from a malaria risk area

P. falciparum can progress to severe and life-threatening illness, including cerebral malaria, if it is not diagnosed and treated promptly. Travellers returning from malaria risk areas should seek urgent medical advice, including a same-day result malaria blood test, for any symptoms, especially fever, during their trip or in the year following their return home.

Treatment guidelines and algorithms for clinicians are available from the British Infection Association.

Reliability of malaria diagnostic tests

In the UK, malaria is diagnosed by microscopic examination of thick and thin blood films and by rapid immunochromatographic diagnostic tests (RDTs) which detect circulating parasite antigens. RDTs have satisfactory diagnostic accuracy in most clinical situations but should not be relied on alone (13). The most commonly used RDTs detect circulating P. falciparum histidine-rich proteins (HRP2 and HRP3). However, deletions of pfhrp2 and pfhrp3 genes occur in some P. falciparum populations, particularly in regions of the Amazon River basin in South America, and in East Africa, reducing the sensitivity of some RDTs (14). Among 113 UK P. falciparum samples from East Africa in 2018, 23 (20.4%) showed evidence of deletion of at least one of these 2 genes (15). The MRL has characterised in detail a further 5 cases where a false-negative HRP2 RDT result was obtained by the sending laboratory, prior to confirmation of P. falciparum infection by microscopy (16).

The implications of pfhrp2 and pfhrp3 gene deletions for RDT use is under investigation by the WHO, and further guidance is expected, but these tests remain an important additional diagnostic tool for imported malaria in the UK. In the UK, blood film microscopy is of a high standard and should be performed on all suspected malaria cases, whether or not an RDT is used. The British Society for Haematology Guidelines for the laboratory diagnosis of malaria, revised in May 2022 (16), provide the necessary guidance.

Antimalarial treatment failure in UK patients

In 2017, the MRL reported 4 cases of treatment failure among UK patients receiving artemether-lumefantrine (Riamet™) for P. falciparum infections (17). Since that time a further 21 suspected cases have been reported and are under investigation by the MRL. Initial treatment failures represent a tiny but increasing proportion of notified P. falciparum cases in the UK – in 2019, 8 suspected P. falciparum post-treatment recurrences were identified by passive surveillance at the MRL, out of a total of 1,475 reported cases (0.05%).

Riamet™ (artemether-lumefantrine) remains highly effective and recommended for treatment of UK cases. However, clinicians should be aware of this issue, and of the potential need for prolonged or alternative treatment in rare cases of parasite recrudescence.

Eurartesim (piperaquine tetraphosphate-artenimol) is also recommended in national guidance. In September 2022 the first case of artemisinin-resistant P. falciparum carrying the variant pfk13_675V was detected in the UK in a UK resident following travel to Uganda. The MRL continues to monitor closely for further evidence of artemisinin-based combination (ACT) treatment failure in the UK.

Prevention is key

Malaria, an almost completely preventable but potentially fatal disease, remains an important issue for UK travellers. Failure to take chemoprophylaxis correctly is associated with the majority of cases of malaria in UK residents travelling to malaria-risk areas. The number of cases in those going on holiday is small but associated with greater mortality (8). Those of African or Asian ethnicity who are non-UK born and who travel to visit friends and relatives are at increased risk of malaria, as well as a number of other infections (18). Older patients and children are at particular risk of dying from malaria if they acquire the infection (11).

Those providing advice should engage with these population groups wherever possible, including using potential opportunities to talk about future travel plans outside a specific travel health consultation, such as during new patient checks or childhood immunisation appointments (19).  The Malaria Reference Laboratory and UKHSA are part of the African Diaspora Malaria Initiative which aims to improve delivery of tailored advice to VFR travellers who suffer the greatest burden of imported malaria.

The UKMEAG guidelines (3) and National Travel Health Network and Centre are available to assist those providing travel health advice, to help travellers to make rational decisions about protection against malaria.

Useful resources for travellers, including translated leaflets, are also available at Malaria: health advice for travellers.

Information regarding malaria incidents, announcements and guidance amendments from the UK Malaria Advisory Group (UKMEAG) can be found at Malaria: news and updates.

References

1. Cathcart SJ, Lawrence J, Grant A, Quinn D, Whitty CJ, Jones J and others. ‘Estimating unreported malaria cases in England: a capture-recapture study’ Epidemiology and Infection 2010: volume 138, issue 7, pages 1,052 to 1,058

2. UKHSA. ‘Imported malaria in the UK: statistics’ (viewed on 27 October 2022)

3. Chiodini PL, Patel D, Goodyer L. Guidelines for malaria prevention in travellers from the United Kingdom, 2023. UKHSA 2023

4. UKHSA. ‘Notifications of infectious diseases (NOIDs)’ (viewed on 27 October 2022)

5. UKHSA. ‘Notified diseases: 2020 annual figures’ (viewed on 27 October 2022)

6. United Nations Statistics Division. ‘Composition of macro geographical (continental) regions, geographical sub-regions, and selected economic and other groupings’ (viewed on 27 October 2022)

7. World Health Organization (WHO). ‘Malaria factsheet’ (viewed on 26 March 2024)

8. Checkley AM, Smith A, Smith V, Blaze M, Bradley D, Chiodini PL and others. ‘Risk factors for mortality from imported falciparum malaria in the United Kingdom over 20 years: an observational study’ British Medical Journal 2012: volume 344, page e2116

9. Broderick C, Nadjm B, Smith V, Blaze M, Checkley A, Chiodini PL, Whitty CJM. ‘Clinical, geographical, and temporal risk factors associated with presentation and outcome of vivax malaria imported into the United Kingdom over 27 years: observational study’ British Medical Journal 2015: volume 350:h1703

10. ONS. ‘Travel trends: 2021’ (viewed on 26 March 2024)

11. WHO. ‘World malaria report 2023’ (viewed on 26 March 2024)

12. Ahluwalia J and others. ‘A systematic review of factors affecting adherence to malaria chemoprophylaxis amongst travellers from non-endemic countries’ Malaria Journal 2020: volume 16, issue 1, page 16

13. Rogers CL, Bain BJ, Garg M, Fernandes S, Mooney C, Chiodini PL, British Society for Haematology. ‘British Society for Haematology guidelines for the laboratory diagnosis of malaria’ British Journal of Haematology 2022: volume 197, issue 3, pages 271 to 282

14. ML Gatton and others. ‘Impact of Plasmodium falciparum gene deletions on malaria rapid diagnostic test performance’ Malaria Journal 2020: volume 19, issue 1, page 392

15. Grignard L, Nolder D, Sepulveda N, Berhane A, Mihreteab S, Kaaya R and others. ‘A novel multiplex qPCR assay for detection of Plasmodium falciparum with histidine-rich protein 2 and 3 (pfhdpr2 and pfhrp3) deletions in polylclonal infections’ EBioMedicine 2020: volume 55, page 102,757

16. Nolder D, Stewart L, Tucker J, Ibrahim A, Gray A, Corrah T and others. ‘Failure of rapid diagnostic tests in Plasmodium falciparum malaria cases among travelers to the UK and Ireland: identification and characterisation of the parasites’ International Journal of Infectious Diseases 2021: volume 108, pages 137 to 144

17. Sutherland CJ, Lansdell P, Sanders M, Muwanguzi J, van Schalkwyk DA, Kaur H and others. ‘pfk13-independent treatment failure in 4 imported cases of Plasmodium falciparum malaria treated with artemether-lumefantrine in the United Kingdom’ Antimicrobial Agents and Chemotherapy 2017: volume 61: pages e02382 to e02316

18. Wagner KS, Lawrence J, Anderson L, Yin Z, Delpech V, Chiodini PL and others. ‘Migrant health and infectious diseases in the UK: findings from the last 10 years of surveillance’ Journal of Public Health 2014: volume 36, issue 1, pages 28 to 35

19. Office for Health Improvement and Disparities (OHID). Migrant health guide (viewed on 27 October 2022)