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Volume 2 No 40; 3 October 2008

No evidence of new variant Chlamydia trachomatis in England and Wales

Initially isolated in Sweden in 2006, new variant C. trachomatis (nvCT) is of public health importance as it contains a 377bp deletion in a portion of the plasmid that is the target area for some C. trachomatis nucleic acid amplification tests (NAAT). Consequently, affected platforms generate false negative results when presented with this strain. Despite being present within the Swedish population at a high prevalence, reports of nvCT outside of Sweden remain relatively rare and have been confined to isolated cases [1]. In August 2008 a single case of nvCT was reported in Scotland [2].

As yet there have been no reports of nvCT in England and Wales despite three large studies having been conducted. Sillis et al, in 2007, screened 1680 genital specimens giving a negative result on an affected platform sourced from four centres in England and retested them on an unaffected platform. Despite finding 29 discrepant specimens (ie those giving a positive result on only one of the two platforms), none were determined to be nvCT [3]. An alternative study screened 1112 specimens which had been confirmed as CT positive, using an unaffected platform, for the presence of the 377bp nvCT deletion. All typable specimens (95.9%) were confirmed as wildtype CT [4]. Finally, in a recent unpublished prospective study (undertaken between August 2007 and January 2008), urine specimens from 695 men with urethritis from 14 different centres throughout the UK who tested negative for CT at their local laboratory were forwarded for confirmatory testing. This approach produced 14 discordant specimens, none of which were identified as nvCT.

The Health Protection Agency's (HPA) Sexually Transmitted Bacteria Reference Laboratory (STBRL) has recently performed a telephone survey which aimed to establish the range and usage of CT NAAT testing platforms in England and Wales (unpublished data). It was determined that only 10% (11/108) of the laboratories surveyed used the only remaining nvCT-affected NAAT platform, Cobas Amplicor (Roche). The remaining 90% of laboratories used CT NAAT technology which can detect both wild type and nvCT. Such data are reassuring as it is thought that the rapid increase in prevalence of nvCT in Sweden was as a result of the selection pressure that was created by the almost exclusive use of the Cobas Amplicor platform (Roche). In England and Wales, given the range of CT NAAT platforms used, it is unlikely that such an event would occur. However, STBRL will be working with a number of diagnostic laboratories to ensure that the situation regarding nvCT in England and Wales is closely monitored.

Current recommendations to diagnostic laboratories in England and Wales

  • Laboratories using either COBAS Taqman CT v2.0 (Roche) or Abbott Real Time CT/NG (Abbott) should ensure that they are using the latest kit versions, which are able to detect nvCT [5].
  • Laboratories performing testing on two platforms (including the Roche Cobas test), should consider using the Cobas Amplicor test (Roche) for confirmation rather than primary testing.
  • Laboratories who are using the Cobas Amplicor platform (Roche) as their only method of C. trachomatis detection should carry on using this approach but be vigilant for obvious decreases in the number of positives cases.
  • All laboratories should look for new alerts containing updated information.

The STBRL has established assays which are able to detect nvCT and would be pleased to assist with any potential discrepant results that may be due to the variant strain: email stbrl@hpa.org.uk

References
1. Savage EJ, Ison CA, van de Laar MJ. Results of a Europe-wide investigation to assess the presence of a new variant of Chlamydia trachomatis. Euro Surveill. 2007; 12(10): E3-4.
2. New variant Chlamydia trachomatis in Scotland. Health Protection Scotland weekly report [online], 42(39), 24 September 2008.
3. Sillis M, Skidmore S, Mallinson H, Todd T, Coupland L, Oliver P, et al. No evidence of the Chlamydia trachomatis variant in the UK. Sex Transm Infect. 2007 Oct; 83(6): 488-9.
4. Alexander S, Ison C. Is new variant Chlamydia trachomatis present in England and Wales? Sex Transm Infect. 2008 Feb; 84(1): 29-31.
5. Health Protection Scotland. Alert: new variant Chlamydia trachomatis detected in Scotland. http://www.documents.hps.scot.nhs.uk/labs/sbstirl/2008-09-alert-nv-c-trachomatis.pdf.

ACDP consultation on updated BBV guidelines

The Health and Safety Executive has published for public consultation the final draft version of revised guidance on legal and safety management aspects of occupational exposure to blood-borne viruses, prepared by the Advisory Committee on Dangerous Pathogens (ACDP) [1]. The new guidance deals specifically with HIV and hepatitis B and C but is relevant to all workplaces where there may be occupational risk to bodily fluids containing BBVs. The final version is to be published as a web-based guide later this year, replacing the original ACDP guidance [2] that has not been previously available in electronic form.

As in the original 1996 version, the guidance covers virology, legal issues, risk assessment and control, and incident management. However, whereas the 1996 guidance focussed on risks in the healthcare sector and laboratories, the updated version covers a wider range of workplace situations where exposure to BBV is possible.

The revised document also provides references (hyperlinked in the final version) to existing, specialist guidance material relevant to a wide range of at-risk occupations, where this is available. This covers, for example, workers in local authorities (eg refuse collection and street cleaning), the emergency services and prisons, as well as other lower-risk situations. Within healthcare, sources of specific advice for laboratories, dentistry, care homes, health-care-related laundry services, etc, are signposted.

Comments are invited on individual sections of the guidance, including on its structure, before Monday 17th November. Suggestions for questions that might be included in a "questions and answers" section are also invited.

References
1. The draft guidance, Protection Against Blood-borne Infections in the Workplace: HIV and Hepatitis (PDF format), and an electronic response form with instructions for responders is available at: http://www.hse.gov.uk/biosafety/diseases/blood-borne-virus.htm
2. Protection against blood-borne infections in the workplace: HIV and hepatitis (ACDP) 1995, HMSO, ISBN 0 11 321953 9.

Confirmed measles cases in England and Wales – an update to August 2008

The total number of laboratory confirmed cases of measles in England and Wales with onset dates between 1 January and the end of August this year has reached 884. The proportion of oral fluid tests that were positive during August was 37% for London and 16% for the rest of England and Wales.

Only 80 cases were confirmed during August (table 1), the first monthly decline since February. This is in contrast to 2007 when the confirmed cases peaked in August (figure 1).

Most of the recent cases were reported from outside London and are linked to travelling communities across England. Cases were reported from several traveller sites in North West, East Midlands and East of England regions. Local HPUs are working with PCTs to offer immunisation to any unvaccinated children as part of the MMR catch-up programme [1]. In addition, several cases were in France during their incubation period and one family (three cases) was diagnosed in Portugal.

Overall this year, the highest proportion of cases is in children of nursery and primary school age (figure 2). The observed decrease in August was expected as it coincides with school holidays. However, coverage of MMR at two years of age remains sub-optimal [2]. A recently published study predicting the number of children susceptible to measles in the population suggests the possibility of a measles epidemic is very real [3].

References
1. MMR catch-up programme announced, Health Protection Report, 2 (32), http://www.hpa.org.uk/hpr/archives/2008/news3208.htm#mmr.
2. COVER programme, April to June 2008: Quarterly vaccination coverage statistics for children aged up to five years in the United Kingdom, Health Protection Report, 2 (39), http://www.hpa.org.uk/hpr/archives/2008/hpr3908.pdf.
3. Choi YH, Gay N, Fraser G, Ramsay M, The potential for measles transmission in England (in press).

Table 1. Confirmed cases of measles by region and month of onset, England and Wales: January - August 2008

Month

London

East Mids

East of England

North East

North West

South East

South West

West Mids

Wales

York & Humber

Jan-08

60

1

8

1

1

1

-

3

1

12

Feb-08

44

-

4

3

-

7

-

-

-

3

Mar-08

67

1

1

-

-

6

1

1

1

5

Apr-08

92

-

8

3

1

6

15

2

-

14

May-08

103

1

6

-

23

6

7

3

-

5

Jun-08

96

-

10

1

22

7

3

5

-

3

Jul-08

67

1

11

-

22

17

3

7

-

2

Aug-08

30

6

5

-

15

17

-

6

-

1

Total

559

10

53

8

84

67

29

27

2

45

 

Figure 1. Number of laboratory confirmed cases in England and Wales by month of onset: January 2007 - August 2008

 

Figure 2. Confirmed cases by age groups targeted by the MMR catch-up programme, England and Wales: January - July 2008

 

Start of the 2008/09 flu reporting season

The first week of October is the beginning of the influenza activity monitoring season and signals the return of reporting on influenza and other respiratory virus surveillance. A welcome note indicating the start of the 2008/09 season was published on Wednesday 1 October [1] and the HPA National Influenza Reports will now be published fortnightly until such time as activity begins to increase; they will then be published weekly. A short summary of activity will be made available in the weeks between the fortnightly reports. The first full influenza report will be published on Wednesday 15 October [2].

References
1. http://www.hpa.org.uk/web/HPAweb&HPAwebStandard/HPAweb_C/1211441457161
2. These reports can be found at: http://www.hpa.org.uk/infections/topics_az/influenza/seasonal/activity0708/weekly_summary.htm

Further information
Influenza season 2007/08 summary: http://www.hpa.org.uk/web/HPAweb&HPAwebStandard/HPAweb_C/1195733836222.