Research and analysis

HPR volume 11 issue 33: news (22 September)

Updated 15 December 2017

Annual review of infections in blood, tissue and organ donors: 2016

PHE has published the joint NHS Blood and Transplant/PHE Epidemiology Unit’s annual review, Safe Supplies: a Baseline for Change, comprising a series of infographics to describe infections among blood, tissue, and organ donors and transfusion recipients during 2016 [1]. Each infographic summarises key findings from the blood, tissue and organ surveillance programmes, and emphasises the safety of the supplies. The title refers to the changes in the blood, tissue and cell donor selection criteria made following a review of behaviours which may increase the risk of infection being acquired – by the Advisory Committee on the Safety of Blood, Tissues and Organs (SaBTO) which advises UK ministers and health departments [2]. These changes will be implemented very soon. The epidemiology unit’s data will be used as a baseline to monitor any impact of the change. A set of data tables are published separately [1].

Out of two million whole blood and platelet donations made in the UK in 2016, only 200 were positive for the mandatory markers of infection and thus removed from the supply. This represents a very low rate of positivity – one in 10,000 donations – with markers of hepatitis B and syphilis the most common. Generally, positive donors had previously undiagnosed chronic infections, only five viral infections (two HIV and three HBV) were likely to have been acquired within 12 months, suggesting donor selection is very effective at identifying low risk individuals. The risk that testing could miss a positive donor remains extremely low, with undetected HBV, HCV and HIV infections estimated at less than one in a million donations. Bacterial screening is also in place across all UK blood services, with detection rates remaining relatively constant year-on-year.

Transfusion-transmitted infections continue to be extremely rare. In 10 years (2007-2016), only 10 bacterial and 10 viral incidents have been confirmed. Most of these viral infections were due to hepatitis E virus (HEV) transmitted prior to the introduction of routine screening.

The HEV infographic documents the joint surveillance and research activities of PHE and NHSBT which contributed to the SaBTO recommendation to screen components for specific patient groups who may be at risk of developing persistent HEV infection. In spring 2016, UK blood services began testing some blood and all apheresis platelet donations for HEV RNA to meet the requirements. The positivity rate varied throughout the year, ranging from 0.09% in May to 0.01% in November; since HEV is most likely acquired through food and there is no specific donor selection, fluctuation among the donor population is directly linked to changes in the epidemiology within the general population.

The new review concludes that there is a robust process in place for the control of current and future infectious risks for blood safety. This is mainly in the context of blood donation but may have implications for tissue and organ donation too. Each year the unit works closely with colleagues in PHE to monitor emerging infections such as Zika and the impact of PHE advice on donor selection. The donor travel survey carried out by the unit in 2016 has enabled NHSBT to gain a better understanding of where donors travel and the activities that they engage in whilst overseas.

The above is an abridged version of the full review published on the PHE website [1].

References

1. PHE website (November 2016). Safe Supplies: Annual Review.

2. PHE website (July 2017). Donor Selection Criteria Report (2017).

Role of WGS in TB cluster investigation reported at Warwick conference

Evidence of the speed and discriminatory power of WGS for TB cluster investigation and control was presented at the recent PHE annual conference at Warwick University [1].

Since December 2016, all mycobacterial isolates received by PHE National Mycobacterial Reference Service laboratory from north and central England have been analysed using whole genome sequencing, replacing the previously-used MIRU-VNTR technique. To date, more than 950 TB isolates have been sequenced by NMRS since December and approximately 15-20 WGS clusters per month are being routinely detected across five PHE Centres.

The Warwick presentation described how use of WGS has significantly shortened the time between receipt of positive cultures by the reference laboratory and production of results that can be used to guide interventions and the help break transmission chains: typically from 4-6 weeks to one week. In addition, phylogenetic information from WGS data allows visualisation of outbreaks and, combined with other epidemiological information, permits interventions to be better targeted. Evidence of strain resistance to anti-tuberculous drugs is also now more rapidly generated – thus expediting effective treatment.

Making the presentation on behalf of a multidisciplinary team comprising microbiologists, epidemiologists, public health practitioners and clinicians, consultant microbiologist Esther Robinson noted that whereas the cost-effectiveness of the previously-deployed, MIRU-VNTR-based surveillance regime had been questioned, studies remained to be done for WGS. However, the increased speed and resolution of WGS are highly promising and cost-effectiveness studies are being planned.

WGS for TB diagnosis and typing is delivering tangible clinical and public health benefits, Robinson concluded; WGS was a “disruptive technology” that was triggering a reappraisal of the previously-operated TB control regimes and necessitating new ways of working.

Reference

1. “Using innovative technology to rapidly shut down TB transmission chains”, session 28, PHE annual conference 2017.

Mandatory HCAI reports quarterly trends: April to June 2017

PHE’s latest quarterly epidemiological commentary on trends in reports of Staphylococcus aureus (MRSA and MSSA) and Escherichia coli bacteraemia, and of Clostridium difficile infections, mandatorily reported by NHS acute Trusts in England up to April-June 2017, has been published on the GOV.UK website [1].

The report includes tabular and graphical presentation of data for the quarter and updates the previous report published in June 2017. Some key facts are listed below.

MRSA bacteraemia

There was a steep decline in the rates of all reported and hospital-onset cases between April-June 2007 (April-June 2008 for hospital-onset cases) and January-March 2014 – 85% (10.2 to 1.5 cases per 100,000 population) and 79% (4.9 to 1.0 cases per 100,000 bed-days), respectively.

However, since January-March 2014 the rates of all reported cases increased slightly from 1.5 to 1.6 cases per 100,000 population while hospital-onset cases decreased slightly from 1.0 to 0.9 cases per 100,000 bed-days), when compared to the most recent quarter, April-June 2017.

The PIR process for all MRSA bacteraemia cases began in April 2013. Between April 2013 and March 2014, the rates of trust-assigned cases remained stable at 1.2 cases per 100,000 bed-days while rates of CCG-assigned cases decreased by 22% from 1.0 to 0.8 cases per 100,000 population.

Following the introduction of a third-party assignment category in April 2014, counts and rates of CCG-assigned cases have decreased from 91 to 86 cases and 0.7 to 0.6 cases per 100,000 population, respectively, between April-June 2014 and the most recent quarter. This decrease is mostly due to the introduction of the new assignment category, as several cases which would be classified as CCG-assigned are now classified as third-party assigned.

Over the same period (April-June 2014 to April-June 2017), counts and rates of trust-assigned cases increased from 73 to 83 cases and 0.8 to 1 case per 100,000 bed-days, respectively. Similarly within the same period, counts and rates of third-party assigned cases increased from 17 to 50 cases and 0.1 to 0.4 cases per 100,000 population, respectively.

MSSA bacteraemia

The counts of MSSA bacteraemia have increased by 36% (2,199 in Q4 2010/11 to 2,995 in Q1 2017/18) and the rates have increased by 31% (16.9 cases per 100,000 population in Q1 2010/11 to 21.8 in Q1 2017/18). Counts and rates of hospital-onset MSSA bacteraemia over the same period (January-March 2011 to January-March 2017) increased at a much slower pace: 11% (from 735 to 813 cases) and 4% (8.4 to 9.3 cases per 100,000 bed-days), respectively.

Rates of all reported and hospital-onset cases from earlier quarters between January-March 2011 and October-December 2013 were relatively stable, fluctuating between 16-17 cases per 100,000 population and 7-8 cases per 100,000 bed-days, respectively. However, subsequent quarters (January-March 2014 to April-June 2017) saw an increase in the rates of all reported and hospital-onset MSSA bacteraemia by 21% (18.1 to 21.8 cases per 100,000 population) and 18% (7.9 to 9.3 cases per 100,000 bed-days), respectively.

While the number of all reported MSSA bacteraemia increased throughout the surveillance period (January-March 2011 to April-June 2017), the percentage of all cases that were defined as hospital-onset decreased over the same the period from 33% to 27%, indicating that over time there has been a greater increase in community-onset cases compared to hospital-onset (hospital-onset) cases.

E. coli bacteraemia

Counts and rates of all reported E. coli bacteraemia increased by 23% (8,275 to 10,182 cases) and 20% (61.7 to 74.0 cases per 100,000 population), respectively, between July-September 2011 and April-June 2017, with seasonal peaks generally reported between July and September each year. While these seasonal fluctuations are present - beginning from April-June 2013 - each quarter of each year has been higher than the same quarter in the preceding year, implying an overall increase over the overall time period. However, counts and rates of hospital-onset cases decreased from 1,996 to 1,976 cases and from 23.7 to 22.7 cases per 100,000 bed-days over the same period.

A similar trend is also observed when comparing the most recent quarter with the same period last year (April-June 2016 to April-June 2017). There was a 3% increase in both counts and rates of all reported cases (9,850 to 10,182 cases and 71.6 to 74.0 cases per 100,000 population) while both counts and rates of hospital-onset cases reduced slightly by 1% (1,991 to 1,976 cases and 22.9 to 22.7 cases per 100,000 bed-days).

C. difficile infection (CDI)

Since the initiation of CDI surveillance in April 2007, there has been an overall decrease in the counts and rates of all reported and and hospital-onset cases of C. difficile infection (CDI). Seasonal peaks were present in the January-March quarters prior to 2014/15 and the July-September quarters of 2014/15 to 2016/17, this is particularly apparent among hospital-onset cases. The bulk of this decrease occurred between April-June 2007 and January-March 2012 with a 78% and 79% reduction in both counts and rates (16,864 to 3,711 cases and 131.5 to 28.0 cases per 100,000 population, respectively), followed by an 11% and 14% reduction in the counts (3,711 to 3,299 cases) and rates (28.0 and 24.0 cases per 100,000 population) of CDI between January-March 2012 and the most recent quarter (April-June 2017).

A similar trend was observed in hospital-onset CDI counts and rates between April-June 2007 and January-March 2017: 85% (10,436 to 1,613 cases) and 84% (112.5 to 18.2 cases per 100,000 bed-days), respectively, This was then followed by a further 30% decrease in counts (1,613 to 1,132 cases) and rates (18.2 to 12.3 cases per 100,000 bed-days) of hospital-onset cases between January-March 2012 and the most recent quarter.

This shows that there has been a greater decline among trust-apportioned CDI cases compared to all reported CDI cases during the surveillance period.

Reference

1. PHE (14 September 2017). Quarterly Epidemiological Commentary: Mandatory MRSA, MSSA and E. coli bacteraemia, and C. difficile infection data (up to April-June 2017).

Health protection in schools and other childcare facilities

PHE has published a practical guide on infection prevention and control in schools, nurseries and other childcare settings [1]. Intended for staff working in these settings, it reviews the general principles of IPC, how to minimise/prevent spread of infection, how to manage cases of disease (including when an infected child/staff member should be excluded from their school/nursery in order to protect others) and when to seek specialist advice.

The guide comprises nine main chapters, covering:

• principles of infection prevention and control;
• instances when the local PHE Health Protection Team should be notified, ie:
  • in the event of single cases of measles, meningitis or other notifiable disease
  • in the event of an outbreak (eg food poisoning, influenza, scarlet fever, etc)
• cleaning standards and schedules, including for toys and following blood and body fluid spills
• the UK Childhood Immunisation Schedule and recommendations for staff immunisation
• the requirement for a written policy on exclusion of staff such as food handlers
• minimising risk associated with school excursions, water-based activities, petting farms, etc, and
• advice on managing 37 specific infections which are most commonly associated with children and young adolescents – campylobacter, cryptosporidiosis, salmonella, VTEC, scabies and scarlet fever – and vaccine-preventable infections such as measles, meningitis, rotavirus.

One of three annexes comprises a checklist for dealing with outbreaks of diarrhoea and vomiting.

1. PHE website (September 2017). “Health protection in schools and other childcare facilities”.

New website for Eurosurveillance

ECDC’s peer-reviewed weekly public health journal, Eurosurveillance, is being re-launched on a new website with effect from Monday 25 September (1300 hours, CET) [1]. The EU agency has informed existing subscribers that they will need to register on the new website, after it is launched, in order to continue receiving the weekly Table of Contents e-mail. The URL of journal’s website will be unchanged: www.eurosurveillance.org.

Re-registration is necessary because all personal data collected from those registered on the old site will be destroyed (in order to comply with EU data protection requirements) and existing subscribers’ e-mail addresses cannot therefore automatically be transferred to the new journal’s subscription fulfilment database.

The new site will offer a number of new functionalities, including: the ability to download PowerPoint files for figures and tables; article-level metrics; a citation export feature; social bookmarking; and a more refined search (including “saved search alerts”, whereby users can be automatically notified when a paper covering a topic of particular interest is published).

Reference

1. “Note from the editors: Wave goodbye and say hello - Eurosurveillance to launch new website soon”, Euro. Surveill. 22(38), 21 September 2017.