Research and analysis

HPR volume 9 issue 31: news (4 September)

Updated 29 December 2015

1. National outbreak of Escherichia Coli VTEC O157 PT8 VT2

In early August 2015 a number of cases of Verocytotoxigenic Escherichia Coli (VTEC) serotype O157 phage type 8 vero-toxin type 2a (MLVA profile 17-9-6-13-8-4-5-5 or a single locus variant thereof) were found to be genetically clustered by whole genome sequencing (WGS) and to share the same SNP address.

As of 3 September, the cluster comprises 38 confirmed cases, with one additional probable case and four possible cases for which WGS results are pending. Onset dates for confirmed and probable cases range from 29 July to 12 August 2015. Cases are widely distributed across England, with one case in Wales but none identified in Scotland to date. In England, the majority of confirmed cases (seven each) have been reported from Anglia and Cheshire and Merseyside, with 14 additional Health Protection Teams across the country also affected and reporting between one and three cases each. Most cases are female aged 18 to 73 years.

Analysis of enhanced VTEC questionnaires has shown that 33/38 confirmed members of the cluster had exposure to pre-packed salad and that 19 of these had purchased their prepacked salad at the same supermarket chain. A focused survey carried out with 24 of the confirmed cases indicated that the most common exposures were to two salad products from one supermarket chain which share one ingredient. Trace-back has been initiated and one packer/distributor has been identified which is supplied by three farms. Samples are being collected from the supermarket chain outlets visited by cases, the distributor/packer and from the supply farms. Investigations to determine the exact source and cause of contamination are on-going.

Outbreak control team (OCT) meetings were held on 19 August, 24 August and 1 September. The OCT is comprised of epidemiological and laboratory scientists from the Gastrointestinal Infection Department of PHE’s National Infection Service, scientists from the PHE Food, Water and Environment laboratory, representatives of local PHE HPTs with cases in their area, and representatives of the Food Standards Agency.

2. Prenatal pertussis vaccine coverage 2014-15 annual report

A new analysis of the coverage achieved by the prenatal pertussis immunisation programme in England, for the year April 2014 to March 2015, has been published by PHE [1].

Data for women who gave birth in the year were automatically extracted from 94% of GP practices in England and monitored, validated and analysed by PHE. The annual report provides a more detailed analysis of coverage than in recently published quarterly reports [2]. Ethnicity data is included in the new analysis for the first time.

Although laboratory confirmed pertussis cases in infants under three months of age have remained low since the immunisation programme began in autumn 2012, incidence in those aged one year and older has continued to be higher than before 2012 [3]. PHE has issued a press release calling for pregnant women to take up the pertussis vaccine in order to protect themselves and their babies [4].

2.1 References

1. PHE (September 2015). Prenatal pertussis imunisation programme 2014/15: annual vaccine coverage report for England.

2. “Pertussis immunisation in pregnancy: vaccine coverage estimates (England)” webpage.

3. Laboratory confirmed pertussis in England: data to end-June 2015, HPR 9(30), 28 August 2015.

4. “New whooping cough figures prompt call for pregnant women to get immunised”, PHE press release, 3 September 2015.

3. Ebola virus disease: international epidemiology summary (at 30 August 2015)

The West African Ebola virus disease (EVD) outbreak continues with case incidence in the affected countries remaining at three confirmed cases for five consecutive weeks (see figure).

As of 30 August 2015, a total of 28,109 clinically compatible cases of EVD (15,226 confirmed) including 11,305 deaths, have been reported associated with the West African outbreak.

In the last fortnight, a total of six cases have been reported, five in Guinea and one in Sierra Leone. The Guinean cases have been reported in two prefectures, Conakry the capital (four cases) and Dubréka (one case), with ongoing occurrence of cases emerging from unknown sources. The single case in Sierra Leone was detected following a community death in the district of Kambia, an area which last reported a case in early July. Investigations into the source of infection for this case continue. Vaccination is currently being undertaken in Guinea and Sierra Leone of all adult contacts of confirmed cases.

Following 42 days since the second negative test on the last case, Liberia was declared EVD transmission free on 3 September and now enters a 90 day period of heightened vigilance.

Number of new confirmed cases reported per week (17 May to 15 August 2015) in affected countries in West Africa. (Data Source: WHO Ebola Situation Report 2 September 2015)

Further information on the epidemiological situation can be found in PHE’s weekly Ebola epidemiological update and from the Ebola outbreak distribution map.

4. Cyclospora outbreak related to travel to Mexico: an update

The outbreak of cyclospora associated with travel to Mexico, previously reported in HPR on 24 July [1], has been ongoing since 1 June 2015. As of 2 September 2015, 69 cases with known travel to Mexico have been reported in England, Scotland and Wales, of which 39 have been confirmed by a reference laboratory. A further six cases in England are awaiting travel history information.

Where information is known, cases have been to various hotels and resorts on the Riviera Maya coast of Mexico, most of which also have their own water supply, suggesting the source is likely to be a food product that was distributed to several hotels.

The latest known date of onset of illness for cases is 7 August 2015. Onset dates are awaited for a further 11 cases recently reported in England, therefore it is unclear at present if the outbreak is still ongoing.

The UK travel industry is aware of the outbreak and tour operators have been given information about cyclospora in order increase awareness of the infection among travellers to Mexico. Investigations into the cause of the outbreak by Mexican health authorities are ongoing.

Given that it is not clear if the outbreak has ceased, it is recommended that patients returning from Mexico with diarrhoea continue to be tested for Cyclospora Cayetanensis. Cases in England should be reported to the PHE local health protection team and positive faecal specimens referred to the National Parasitology Reference Laboratory, Hospital for Tropical Diseases for confirmation and typing. Specimens in Wales and Scotland can be sent to the Cryptosporidium Reference Unit in Swansea and the Scottish Parasite Diagnostic and Reference Laboratory in Glasgow respectively.

Information about cyclospora for the public is available on the NHS Choices website.

Health advice for travellers to Mexico, including advice on food and water hygiene, is available from the National Travel Health Network and Centre.

4.1 Reference

1. Cyclospora outbreak related to travel to Mexico, HPR 9(26), 24 July 2015.