Skip to content

News Archives

  

Volume 5 No 40; 7 October 2011

Seventh annual review of infections among UK blood/tissue donors and transfusion recipients

The NHS Blood and Transplant/HPA Epidemiology Unit seventh annual review, Safe supplies: focusing on epidemiology, describes infections among blood and tissue donors and transfusion recipients during 2010 has been released [1]. In addition, the report also includes the most recent estimated risks of current donation testing strategies not identifying an infectious donation, as well as information about antenatal samples tested by NHSBT.

During 2010, almost 2.5 million blood donations were tested in the UK, of which 286 tested positive for one or more of the mandatory markers of infection (HBV, HCV, HIV, HTLV and treponemal antibodies), equivalent to 11.7 confirmed positive donations per 100,000; almost half that seen in 1996 (19.9) . New donors were more likely to test positive than repeat donors, and accounted for four out of every five confirmed positive donations, yet they represented only one in 10 blood donors.

In the UK, hepatitis B (HBV) was the most frequently detected infection in blood donors with 91 donors testing positive for HBV, 7% of which were classified as acute infections. Markers of hepatitis C (HCV) infection were detected in 80 donors, including 10 donors who had been tested in the previous three years ie seroconversions. The number of donors testing positive for treponemal antibodies remains at a similar rate year-on-year, during 2010, 75 donors tested positive, however, these results reflected past infections. No acute syphilis infections were identified in 2010. HIV and HTLV infections were identified in a small number of donors. A total of 18 donors tested positive for HIV infection of whom 17 were male. HTLV infection was reported in 22 donors, of whom 80% were female, and four classified as seroconversions.

During 2010, NHSBT tested samples from 530 deceased tissue donors in England, Scotland and Northern Ireland, one of whom tested positive for treponemal antibodies and was likely to have reflected a long past infection. A total of 4,006 living bone donors were tested in England, three of whom tested positive; one donor for chronic HBV and two had treponemal antibodies reflecting past infection. Hepatitis B anti-core (anti-HBc) is a mandatory marker for tissue donations, two deceased and 10 living bone donors tested positive for anti-HBc with immunity below 100 mIU/ml.

Data collected between 2008 and 2010 were used to estimate the risk of an infectious blood donation not being identified and entering the blood supply. These estimates suggest that we would expect to see two HBV infections per year, one HCV every 10 years, one HIV infection every two to three years and one HTLV infection every three years. However, there have been no confirmed viral transfusion-transmitted infections reported since 2005.

The infection surveillance data gathered by the NHSBT/HPA Epidemiology Unit are distributed widely throughout the UK blood services and are used to inform decisions about donor selection, need for testing and wider public health matters. Supplementary data to the 2010 annual review [2], and information about the unit's data sources and collection methods [3], are available from the Blood-borne Infections in Blood and Tissue Donors (BIBD) pages of the HPA website. In addition, surveillance data are published periodically in Health Protection Report.

References

1. Safe supplies: focusing on epidemiology. NHS Blood and Transplant/Health Protection Agency Centre for Infections Epidemiology Unit annual review. Downloadable from the HPA website: Publications > Infectious diseases > Bloodborne infections > Safe supplies: focus on epidemiology.

2. Annual review from the NHS Blood and Transplant/HPA Centre for Infections Epidemiology Unit, 2010: supplementary data tables. Downloadable from HPA website: Publications > Infectious diseases > Bloodborne infections > Safe supplies: focus on epidemiology.

3. NHS Blood and Transplant/Health Protection Agency Epidemiology Unit: data sources and methods. Downloadable from HPA website: Publications > Infectious diseases > Bloodborne infections > Safe supplies: focus on epidemiology.

Outbreak of UK acquired Shigella flexneri in men who have sex with men

The HPA is currently investigating an outbreak of Shigella flexneri among men who have sex with men (MSM). In July Greater Manchester Health Protection Unit identified an increase in UK acquired cases of the infection. To date, 14 reports have been received predominantly among MSM, aged between 30-50 years, some of whom are HIV positive. In London, an increase in Shigella flexneri was noted during 2010/11 and enhanced surveillance since May 2011 found that 5/16 cases were in MSM. All but one case in MSM in London and Manchester to date are serotype 3a. Pulsed field gel electrophoresis, (PFGE) was performed on three Greater Manchester cases and four London cases. This showed that one London and two Manchester isolates were indistinguishable.  Preliminary investigation has not identified a common venue or point source.  The epidemic curve indicates ongoing transmission rather than a point source (see figure).

Date of onset of UK acquired Shigella flexneri, London and Manchester, since May 2011 (n=29)Date of onset of UK acquired Shigella flexneri, London and Manchester, since May 2011 (n=29)

Man is the only significant reservoir of Shigella infection and infection may follow ingestion of as few as 10 organisms.  The incubation period is between 12 and 96 hours; the infectious period is primarily during the diarrhoeal illness; however cases maintain a low level of infectivity for as long as the organism is excreted in the stool [1].  Shigella species may survive for up to 20 days in favourable environmental conditions and this may lead to transmission through contact with contaminated fomites.

Sexual transmission of Shigella infection was first reported in the United States during the 1970s with most infections in men who have sex with men [2, 3]; in 2006, an outbreak of Shigella sonnei among MSM in London coinciding with a similar outbreak in Berlin was reported [4].  Investigation of Shigella infection among MSM via a case control study in New South Wales in 2000 found that visiting a sex venue in the two weeks before illness was significantly associated with shigellosis and the authors concluded that transmission may have occurred directly during casual sex or indirectly from contact with contaminated surfaces or douching equipment [5].  Sexual transmission of shigellosis is likely to be fuelled by the low infectious dose, immunodeficiency due to HIV infection and serosorting (sex between partners with the same HIV status) [6].  Travel may also play a role in introducing Shigella species to populations at risk [6].

Health Protection Units and health professionals who work in sexual health are asked to be alert for cases of Shigella flexneri acquired in the UK among MSM.  Patients presenting with acute diarrhoea should have a stool sample taken for culture with a specific request for Shigella  testing [7,8]. To help interrupt onward transmission, patients with laboratory confirmed infection should be treated with ciprofloxacin, subject to antimicrobial sensitivity. Of seven isolates tested thus far, all have been sensitive to ciprofloxacin. However, the emergence of resistance to ciprofloxacin needs to be monitored closely and, if necessary, antimicrobial treatment switched to ensure treatment remains effective. The following recommendations may also help reduce transmission: avoiding sex until recovery, washing hands thoroughly when preparing and eating food, after going to the toilet and, if patients do have sex, before and afterwards. The HPA is working with the British Association for Sexual Health and HIV and the Terrence Higgins Trust to raise awareness among clinicians and MSM. Updated health information will be available on the HPA website shortly.

It is recommended that all Shigella isolates should be sent to the national reference laboratory, the Laboratory of Gastrointestinal Pathogens, HPA, Microbiology Services Colindale. Maximising case ascertainment will be crucial for infection control and microbiologists and clinicians are reminded that Shigella infection should be reported to the HPA and cases of infectious bloody diarrhoea should be notified to the Proper Officer, normally the Consultant in Communicable Disease Control.

References

1. Hawker J, Begg N, Blair I, Reinitjes R, Weinberg J.  Communicable Disease Control Handbook, second edition.  Blackwell Publishing Ltd, 2005.

2. Dritz SK, Back AF.  Shigella enteritis venereally transmitted [letter]. N Engl  J Med 1974; 291:1194.

3. Drusin LM, Genvert G, Topf-Olstein B, Levy-Zombek E,  Shigellosis. Another sexually transmitted disease?  Br J Vener Dis 1976; 52:348-50.

4. Morgan O, Crook P, Cheasty T, Jiggle B, Giraudon I, Hughes H et al.  Shigella sonnei outbreak among homosexual men, London.  Emerg Infect Dis 2006; 12:1458-1460.

5. O'Sullivan B, Delpech V, Pontivivo G, Karagiannis T, Marriott D, Harkness J, McAnulty JM.  Shigellosis linked to sex venues, Australia.  Emerg Infect Dis 2002; 8:862-864

6. Daskalakis DC, Blaser MJ.  Another perfect storm: Shigella , men who have sex with men and HIV.  CID 2007;44: 335-7.

7. Health Protection Agency (2010). Investigation of faecal specimens for bacterial pathogens. National Standard Method BSOP 30 Issue 7. http://www.hpastandardmethods.org.uk/pdf_bacteriology.asp.

8. Health Protection Agency (2007). Identification of Shigella species. National Standard Method BSOP ID 20 Issue 2. http://www.hpa-standardmethods.org.uk/pdf_sops.asp.

Investigation into an increase in Salmonella Typhimurium DT 193 infections in England and Wales

An increase in the number of received isolates being typed as Salmonella Typhimurium definitive type 193 (DT 193), particularly isolates exhibiting resistance to ampicillin, streptomycin, sulphonamides and tetracyclines (ASSuT), has been noted by the HPA Health Protection Services' gastrointestinal and emerging zoonotic infections department (GEZI). The increase has been gradual over the past two years and has been investigated on three previous occasions with inconclusive results.

The increase this year follows a rise, and subsequent fall, seen in 2009-2010, which was investigated on three occasions with inconclusive results.

Reports have exceeded previous seasonal limits since July 2011, with 97 indigenous cases reported between July and September 2011 (weeks 29-37), compared with 60 over the same period (weeks 29-37) in 2010, and 38 in that period in 2009. This increase appears to be part of an overall annual increase in incidence which started in 2009 (see figure). Specimens have been reported from all regions in England, and from Wales.

Monthly frequency distribution of non-travel associated Salmonella Typhimurium DT 193 (ASSuT resistant), 2005 - 2011 Monthly frequency distribution of non-travel associated Salmonella Typhimurium DT 193 (ASSuT resistant), 2005 – 2011

In 2011, the gender distribution is 1:1 (126 male, 125 female, four unknown), and cases range in age from one month to 88 years of age, with a mean of 37 and median 35 years of age, although 22% of cases are under the age of 10. The current situation is indicative of an ongoing persistent outbreak of this subtype and resistance profile.

Given the regional and temporal distribution of the current increase in DT 193 (ASSuT), there is a need to determine whether this reflects a common source national distribution issue, and to ascertain the vehicle of infection. Outbreak clusters have been reported throughout 2011, associated with events where "hog roasts" have been provided [1], and there are known associations between this phage type and both pork and beef products. Between December 2010 and June 2011, Health Protection Services staff have undertaken trawl interviews with 11 cases and also received local Environmental Health Questionnaires for a further 37 cases. Preliminary analysis of all questionnaires indicates a higher than expected frequency of exposure to beef, notably minced beef, and pork products, notably ham and pork sausages. In addition, exposure to chicken was high, but within expected range for this food type when compared against recent outbreak investigation datasets (non-travel VTEC, 2011) and Salmonella Enteritidis PT14b (June-August, 2011).

The GEZI department of HPS at Colindale are currently investigating this increase further with an analytical case control study.

References

1. Outbreaks of Salmonella Typhimurium DT 12 and DT 193 associated with hog roasts in the South West Region in April 2011, HPR 5(21), 27 May 2011.

Publication of MRSA bacteraemia and Clostridium difficile infection data from the independent healthcare sector

The third set of six-monthly data on meticillin-resistant Staphylococcus aureus (MRSA) bacteraemia and Clostridium difficile infection (CDI) for independent sector (IS) healthcare organisations have been published on the HPA website [1]. The newly published data now provides a full financial year of data for the period April 2010 to March 2011.

This publication is also the first for the IS to calculate rates using a new modified bed-day denominator of bed-days plus discharges as this denominator is more appropriate for facilities providing mainly short-stay treatment, such as the IS. The rates and denominator in the archive financial year data for April 2009 to March 2010 have also been updated.

This modified bed-day denominator and a number of other factors make the published data on MRSA bacteraemia and CDI incomparable between the IS and NHS (see table).

Summary of key difference between reporting in the NHS and IS
Independent sector organisations NHS acute Trusts

Organisation level reporting

Trust level reporting

Primarily elective patient-mix

Broad patient-mix including emergency based treatments

Constantly changing facility list

Mainly static list of providers

Large number of specialist facilities

Mainly general acute facilities

Organisations may comprise geographically diverse hospitals

Mainly local clusters of hospitals

Not all organisations/hospitals capable of reporting using the web-enabled DCS

All NHS Trusts capable of reporting using the web-enabled DCS

Rates calculated using bed-days plus discharges due to the high proportion of day cases compared to the NHS.

Rates calculated using bed-days (occupied beds at midnight).

Reference

1. HCAI Reporting within independent sector healthcare organisations. HPA website: Topics > Infectious Diseases > Infections A-Z > Healthcare Associated Infections (HCAI) > Epidemiological Data on HCAI > HCAI Reporting within Independent Sector healthcare organisations.