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Published: 28 September 2006 Volume 16, No.39 (PDF file, 211 KB)

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• Two contiguous but unconnected outbreaks of Vero cytotoxin-producing E coli O157 infection in South East London
• Vaccine to prevent cervical cancer and warts is licensed for use in the UK

Two contiguous but unconnected outbreaks of Vero cytotoxin-producing E coli O157 infection in South East London

Two large outbreaks of Vero cytotoxin-producing E coli (VTEC) O157 occurred in short succession in South East London in June and July 2006.

Bromley Outbreak

On 26 June 2006 the South East London HPU (SELHPU) was informed that over twenty children in a large primary school were reported absent with gastrointestinal symptoms, including hospital admission of one child and one adult with bloody diarrhoea.

Standard immediate outbreak control measures were implemented by SELHPU, yet initial investigations did not reveal a clear source or causal organism. After identification of a presumptive VTEC O157 isolated from a stool sample from one child on 28 June, the outbreak control team (OCT) agreed the following control measures:

1. To close the school with immediate effect to prevent further transmission
2. To screen all pupils and staff attending the school (over 700 people)
3. To deep-clean the school
4. To allow pupils and staff to re-attend the reopened school only after confirmed negative result.

Presumptive E. coli O157 from 43 people (41 children aged from 3 to11 years, and two adults) was confirmed by the HPA Laboratory of Enteric Pathogens (LEP). Isolates belonged to phage type (PT) 21/28 and were positive for Vero cytotoxin 2 (VT2) genes, and negative for VT1. Onset dates for cases ranged from 19 June to 2 July with some clustering around the 22/23 June, suggesting a common point source (figure 1). There were a number of secondary cases in households, and spread to a sibling led to one case in a local nursery. There were 24 cases and 19 asymptomatic carriers. One child was admitted to hospital with haemolytic uraemic syndrome (HUS). SELHPU and the local environmental health department continue investigations to determine the source of the outbreak. A total of 11 isolates were examined by LEP using pulsed field gel electrophoresis (PGFE). Ten isolates had indistinguishable profiles and one strain had a variant profile that was clearly related to the others.

Figure1 Epidemic curve for confirmed cases of E. coli O157 in the Bromley school outbreak

Bexley Outbreak

On 14 July 2006, SELHPU was notified of a presumptive E. coli O157 in a 2 year old child. No links could be established with the other ongoing outbreak in Bromley. On 19 July a second child was reported having attended a local A&E department with bloody diarrhoea. Both children attended the toddler group in the same nursery. The control measures implemented by the OCT were similar to those described above. Including the two initial cases, a total of 16 children (aged 11 months to 8 years) and three adults tested positive for presumptive E. coli O157 PT 21/28. Strain typing and fingerprinting in LEP showed that this outbreak was also caused by a strain of PT 21/28 with genes for VT2. However, the PFGE profile of this strain differed by at least three fragment position from that associated with the Bromley school. Onset dates ranged from 6 to 27 July, and the epidemic curve suggests person to person transmission (figure 2). Telephone completed questionnaires with all cases did not reveal any epidemiological links with the other outbreak. No source could be identified. Two further cases of VTEC O157, PT21/28, VT2 were identified in siblings, one of whom attended the nursery. PFGE showed that the strain was different from both the Bexley and Bromley outbreak strains.

Figure 2 Epidemic curve for confirmed cases of E. coli O157 in the Bexley nursery outbreak

Outbreaks of VTEC O157 have been uncommon in London. These two outbreaks occurred within a few miles, closely one after the other, and in similar settings. Phage type 21/28 is the most common phage type of VTEC O157 in the UK (1) and causes general and household outbreaks and sporadic infections. Strains can be differentiated by PFGE profile. While profiles within each outbreak were largely indistinguishable, there were clear differences in profiles between the outbreaks. This supports the epidemiological findings indicating that both outbreaks were not linked

References

1. HPA. Vero cytotoxin-producing Escherichia coli O157: 2005. Commun Dis Rep CDR Wkly 2006; 16(28): news. Available at: <http://www.hpa.org.uk/cdr/archives/2006/cdr2806>.

Vaccine to prevent cervical cancer and warts is licensed for use in the UK

A vaccine against four types of human papillomavirus (HPV) that cause cervical cancer and warts has been licensed for use in the United Kingdom (UK). The European Commission has granted a license for a quadrivalent vaccine for HPV 16, 18, 6 and 11, manufactured by Merck & Co, Inc., known as Gardasil™. Gardasil will be marketed in the UK by Sanofi Pasteur MSD (SPMSD).

Another vaccine, a bivalent vaccine for HPV 16 and 18, manufactured by GlaxoSmithKline is currently under evaluation by the European Medicines Agency (EMEA). Trials over recent years have shown both vaccines to have high efficacy against infection, cervical intraepithelial neoplasia and, by implication, against cervical cancer caused by the vaccine-types [1].

Gardasil is composed of virus-like particles (VLP) generated by the synthesis and self-assembly of the major human papillomavirus (HPV) capsid protein (L1) in yeast cells ( Saccharomyces cerevisiae ), absorbed on amorphous aluminium hydroxyphosphate sulphate adjuvant. The EMEA license is for use of Gardasil as a vaccine for the prevention of high-grade cervical intraepithelial neoplasia (CIN 2/3), cervical carcinoma, high-grade vulvar intraepithelial neoplasia (VIN 2/3), and external genital warts (condyloma acuminate) causally associated with HPV types 6, 11, 16, and 18 [2]. This is based on demonstration of efficacy in adult females 16 to 26 years of age and on the demonstration of immunogenicity in 9 to 15 year olds. Protective efficacy has not been demonstrated in males. The results of trials in males are expected over the next few years.

The Joint Committee on Vaccination and Immunisation (JCVI), the expert committee that advises the Government on vaccine policy, will make recommendations on the use of HPV vaccination in the UK . Several questions about HPV vaccination efficacy and effectiveness are still under consideration [3]. It is likely that consideration will be given first to the vaccination of young females, before the onset of sexual activity. The NHS Cervical Screening Programme (of women aged 25 to 64 years), and the resulting treatment of cervical disease detected at early stages, has been very successful at reducing the incidence and mortality of cervical cancer in the UK . Screening is expected to remain important for non-immunised women, for older (previously infected) women and for the detection of disease associated with non-vaccine HPV types

HPV infection is well recognised as a causative agent for cervical cancer (and its precursor stages that are the target of cervical screening), with around 70% of cervical cancers in women worldwide associated with HPV types 16 and 18 [4]. In 2002, 2,305 new cases of invasive carcinoma of the cervix uteri were diagnosed in the UK , making it the twelfth most common cancer in women [5]. Pre-cancerous stages of cervical disease are common and often resolve to normal given time, however their follow-up, including repeated screening and examination of the cervix (colposcopy), is associated with considerable costs and anxiety. HPV 6 and 11 are not causally linked to cervical cancer, but are associated with the vast majority of genital warts and with the rare condition of recurrent respiratory papillomatosis [6]. HPV infections are also associated with some rarer tumours of the head and neck and ano-genital area.

References

1. Mounting evidence of the efficacy of human papillomavirus vaccines Eurosurveillance Weekly [serial online] 2006 [accessed 28 September 2006] 2006: 11 (5). Available at <http://www.eurosurveillance.org/releases/index-02.asp?an=2006&display=ew#ew19>

2. EMEA opinion, 27 July 2006. Available at <http://www.emea.europa.eu/pdfs/human/opinion/Gardasil27493806.pdf>

3. Hildesheim A, Markowitz L, Avila MH, Franceschi S. Chapter 27: Research needs following initial licensure of virus-like particle HPV vaccines. Vaccine 2006 Aug 21; 24 Suppl 3:S227-32. Epub 2006 Jun 19.

4. Bosch FX, Lorincz A, Munoz N, Meijer CJM, Shah KV. The causal relation between human papillomavirus and cervical cancer. J Clin Path 2002; 55 :244-65.

5. UK Cervical Cancer incidence statistics In: CancerResearch UK website [online]. Accessed 28 September 2006. Available at <http://info.cancerresearchuk.org/cancerstats/types/cervix/incidence/>

6. Lacey CJ , Lowndes CM , Shah KV . Chapter 4: Burden and management of non-cancerous HPV-related conditions: HPV-6/11 disease. Vaccine 2006 Aug 21; 24 Suppl 3:S35-41.