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Volume 5 No 13; 1 April 2011
Decrease in listeriosis incidence in England and Wales in 2010
Latest data on the incidence of listeriosis in England and Wales show that the number of cases reported to the Health Protection Agency in 2010 was below that seen in recent years but still above those levels seen in the 1990s (see figure).
Listeriosis is a rare but serious food-borne disease caused by the bacterium Listeria monocytogenes. The elderly, the immunocompromised, and pregnant women and their unborn or newborn infants are disproportionately affected. The clinical signs of disease in these groups include septicaemia, meningitis, and miscarriage and the case-fatality rate is high. Deprivation (among all patient types) and being a member of an ethnic minority (among pregnancy associated cases only) have also been shown to predispose to listeriosis [1,2] .
The observed pattern of listeriosis in England and Wales has changed since 2001 [3]. There has been an increase in the number of cases reported (an average of 192 cases reported annually between 2001 and 2009 compared with 110 cases between 1990 and 2000), especially in patients aged 60 years and over. Similar patterns have been reported in other countries in Europe [4,5,6] . The clinical presentation has also changed, with more cases presenting with bacteraemia in the absence of central nervous system involvement [7].
However, in 2010 there was a drop in the number of cases in England and Wales from an average of 199 cases per year between 2005 and 2009 to 156 cases in 2010. While still above the levels observed during the 1990s, this is a noticeable decrease and the lowest numbers reported since 2002 (see figure). However, the number of cases reported so far in 2011 (up to week 12) is higher than that for the same period in 2010 and, once reporting lag time for is accounted for, is likely to be comparable with that seen in earlier years (table 1).The decrease in 2010 is not limited to a particular patient type (pregnancy associated or non-pregnancy associated - figure) nor to a particular region (table 2). The population at risk of listeriosis appears to remain largely unchanged with regards to the distribution of underlying conditions (table 3) and age (66% were 60 years or over between 2005 and 2009 and 65% were in this age group in 2010) among cases. There appear to be proportionally fewer cases infected with serotype 4, amplified fragment length polymorphism (AFLP) type I (seroAFLP type 4 I) reported in 2010 compared to the average for recent years and more with seroAFLP types 1/2a XIV and 4 V (the latter was the most prevalent type in 2010) (table 4).
When surveilling pathogens with a small number of annually reported cases, cases linked to a common source cluster will have a proportionally large impact on the total numbers. However, in 2010 the proportion of cases attributed to a recognised common source clusters was 8% (13) of all cases compared to an average of 1.9% (4) between 2005 and 2009. This could indicate that this reported decrease in 2010 was among sporadic cases in England and Wales and not as a result of fewer clusters. There have been no recent changes to the ascertainment of cases as part of our surveillance and so we have no reason to suspect this decrease is a result of a reporting artefact. However, the ability to detect clusters within the national surveillance dataset was enhanced during 2010 and this may explain the greater proportion of cases ascribed to an outbreak or cluster in 2010 than in previous years.
Laboratories in England and Wales are requested to:- refer all L. monocytogenes isolates from clinical specimens and food samples to Dr Kathie Grant, Foodborne Pathogen Reference Unit, Microbiology Services, Colindale, for confirmation and subtyping (telephone: 020 8327 6505; e-mail: kathie.grant@hpa.org.uk);
- notify local Health Protection Units of cases to ensure effective routine public health follow-up.
Health Protection Units are requested to:complete the standard HPA clinical questionnaire (available from: http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/Listeria/
EpidemiologicalData/listeQuestionnairesforthesurveillanceofListeria/ and return to Piers Mook, Health Protection Services, Colindale (telephone 020 8327 7416; e-mail piers.mook@hpa.org.uk).
Number of cases of listeriosis in England and Wales reported to the HPA by patient type, 1990 - 2010 
Table 1. Cases of listeriosis by patient type for weeks 1-12, 2005 to 2011
Patient type |
2005 |
2006 |
2007 |
2008 |
2009 |
2010 |
2011 |
Non-pregnancy associated |
26 |
16 |
37 |
34 |
35 |
19 |
28 |
Pregnancy associated |
6 |
6 |
6 |
4 |
7 |
4 |
3 |
Total |
32 |
22 |
43 |
38 |
42 |
23 |
31 |
Table 2. Number of cases of listeriosis by region in England and Wales, 2005-2009 and 2010
Patient region |
2005 - 2009* (%) |
2010 (%) |
East Midlands |
14.4 (7.2) |
16 (10.3) |
East |
15.6 (7.8) |
13 (8.3) |
London |
33.2 (16.6) |
23 (14.7) |
North East |
13.6 (6.8) |
12 (7.7) |
North West |
36.4 (18.3) |
17 (10.9) |
South East |
23.4 (11.7) |
25 (16) |
South West |
15.4 (7.7) |
11 (7.1) |
West Midlands |
17.4 (8.7) |
10 (6.4) |
Wales |
10.2 (5.1) |
7 (4.5) |
Yorkshire & Humber |
19.8 (9.9) |
22 (14.1) |
Total |
199.4 (100) |
156 (100) |
Table 3. Number of cases of listeriosis by underlying condition in England and Wales, 2005-2009 and 2010
Underlying condition |
2005 - 2009* (%) |
2010 (%) |
Malignancy |
43.8 (22) |
31 (19.9) |
Multiple conditions |
40.2 (20.2) |
28 (17.9) |
Auto-immune disorders |
13 (6.5) |
5 (3.2) |
Cardiovascular diseases |
5.8 (2.9) |
4 (2.6) |
Renal diseases |
6 (3) |
1 (0.6) |
Other (<5) |
18.6 (9.3) |
15 (9.6) |
Unknown/blank |
38.4 (19.3) |
40 (25.6) |
Not underlying |
33.6 (16.9) |
32 (20.5) |
Total |
199.4 (100) |
156 (100) |
Table 4. Number of cases of listeriosis characterised by molecular typing (SeroAFLP) in England and Wales, 2005-2009 and 2010
Molecular Typing (SeroAFLP) |
2005-2009* (%) |
2010 (%) |
4 V |
23.4 (11.7) |
31 (19.9) |
1/2a XIV |
12.8 (6.4) |
24 (15.4) |
4 IV |
25.6 (12.8) |
22 (14.1) |
4 I |
40.8 (20.5) |
20 (12.8) |
1/2a VII |
16.8 (8.4) |
14 (9) |
1/2b IV |
6.2 (3.1) |
7 (4.5) |
1/2a IX |
11 (5.5) |
6 (3.8) |
1/2b II |
8 (4) |
4 (2.6) |
1/2a III |
5.8 (2.9) |
2 (1.3) |
1/2c VII |
5.6 (2.8) |
2 (1.3) |
Others (<20) |
10 (5) |
11 (7.1) |
No isolate |
33.4 (16.8) |
13 (8.3) |
Total |
199.4 (100) |
156 (100) |
References
1. Gillespie I, et al. Human listeriosis in England, 2001-2007: association with neighbourhood deprivation. Euro Surveill 2010; 15: 27.
2. Mook P, et al. Emergence of pregnancy-related listeriosis amongst ethnic minorities in England and Wales. Euro Surveill 2010; 15: 27.
3. Gillespie IA, et al. Changing pattern of human listeriosis, England and Wales, 2001-2004. Emerg Infect Dis. 2006; 12: 1361-1366.
4. Goulet V, et al. Increasing incidence of listeriosis in France and other European countries. Emerg Infect Dis. 2008; 14: 734-740.
5. Koch J, Stark K. Significant increase of listeriosis in Germany--epidemiological patterns 2001-2005. Euro Surveill 2006; 11: 85-88.
6. Kvistholm JA, et al. Substantial increase in listeriosis, Denmark 2009. Euro Surveill 2010; 15: 12.
7. Gillespie IA, et al. Disease presentation in relation to infection foci for non-pregnancy-associated human listeriosis in England and Wales, 2001 to 2007. J Clin Microbiol. 2009; 47: 3301-3307.