NHSBT and UKHSA epidemiology unit

The NHS Blood and Transplant (NHSBT)) and the and the UK Health Security Agency (UKHSA)) Epidemiology Unit

The NHSBT and UKHSA (formerly Public Health England) Epidemiology Unit comprises a small team of epidemiologists and public health specialists working with scientific and clinical colleagues across both both NHSBT and  and UKHSA. The unit was established in 1995 to monitor infections in blood donors and transfusion recipients. Over time the role of the unit has expanded and we are now responsible for monitoring infections in blood, tissue and organ donors, and transfusion recipients.

Data from the 4 UK blood services areis collated and analysed by the unit to produce surveillance reports and inform/evaluateinform and evaluate policy changes relating to infection risk.

Data fromThese thereports 4 UK blood services are collated and analysed to provide data on the:

• number and rates of infections in donors
• number of donations which would otherwise have been lost if additional tests were not used
• estimated residual risk of a hepatitis B virus (HBV), hepatitis C virus (HCV) or human immunodeficiency virus (HIV) window period donation
• outcome of investigations into suspected post-transfusion infections

NHSBT and  and UKHSA surveillance surveillance programme

The The NHSBT and  and UKHSA surveillance surveillance programme is a series of national schemes managed by the unitunit, which include:including:

• infections in blood donors: monitored through the surveillance of donations tested and the collection of information about infected donors identified.identified
• infections in living surgical bone and deceased tissue donors (for (for NHSBT): monitored in a similar way to blood donors.donors
• infections in deceased organ donors: monitored in a similar way to blood donors.donors
• reported post-transfusion infections: monitoring investigations among transfusion recipients and forms part of of Serious Hazards of Transfusion (SHOT).
• emerging infections: relevant reports from various sources are collated and reported on a monthly basis or as necessary, as a national horizon scanning scheme.scheme
• The Transfusion Medicine Epidemiology Review (TMER) in partnership with the National National CJD Research Research and Surveillance Unit (NCJDRSU) Edinburgh,in Edinburgh: a study which aims to look for evidence of transfusion transmission of Creutzfeld-JakobCreutzfeldt-Jakob Diseasedisease (CJD).)

The following UK and Irish blood services contribute data, which areis used to assess and improve blood and tissue safety:

• NHS Blood and TransplantNHSBT
• Scottish Blood Transfusion Service
• Welsh Blood Service
• Northern Ireland Blood Transfusion Service
• Irish Blood Transfusion Service

Surveillance of infections in blood donors

Every donation is tested for markers of:

• hepatitis B (HBV)
• hepatitis C (HCV)
• hepatitis E (HEV)virus (HEV)
• HIV
• treponemal infections (like syphilis)

Donations are only released to the blood supply if none of these markers are detected.

Donations from new donors and those used for non-leucodepleted components are tested for human TT-cell cell lymphotropic virus (HTLV).

Donations destined for Plasma for Medicine are also screened for hepatitis A virus (HAV) and Parvovirus B19.

Additional testing may be carried out depending on a donor’s relevant history, for example, malaria testing if the donor has recently travelled to a country where malaria is endemic. For further information, see the Joint UK Blood Transfusion and Tissue Transplantation Services Professional Advisory Committee (JPAC) donorguidelines selectionfor guidelinesthe (DSG)UK Blood and Tissue Services.

Surveillance of infections among tissue donors

NHSBT tissue tissue service operates a tissue donation and banking programme from living and deceased donors. Donations include:

• surgical bone (mainly femoral heads)
• skin
• tendons
• heart valves from living and deceased donors

Additionally, Additionally, NHSBT runs runs the NHS cord blood bank. All tissue donors (including cord blood donors) are routinely tested for markers of:

• HBV
• HCV
• HIV
• HTLV infection infection
• treponemal infections (like syphilis)

Surveillance of transfusion transmitted infection (TTI)

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TTI definition definition

A report of an infection suspected to be due to transfusion is classified as a TTI, if the following criteriainvestigation, are met at the end of the investigation:if:

• the recipient had evidence of infection followingpost transfusiontransfusion, of blood components and there was no evidence of infection prior to transfusion and no evidence of an alternative source of infection

and either:

• at least one component received by the infected recipient was donated by a donor who had evidence of the same transmissible infection

or:

• at least one component received by the infected recipient was shown to contain the agent of infection

Lookback investigations are triggered by markers of infection newly identified in returning donors due to a new test that detects a previously undetected infection, post-donation information supplied by a donor, or seroconversion of a returning donor detected on routine screening. These investigations are initiated by the UK blood services and involve reviewing donor history, re-testing archive samples of previous donations where available, tracing components, and identifying and testing recipients.

Viral residual risk estimates in the UK

The viral residual risk for UK blood donations is defined as the risk that a potentially infectious donation is not detected by routine blood donation screening and could potentially be available for transfusion. This is mostly because a blood donation is made during the potentially infectious ‘window period’ (WP) early in the course of infection, when the test in use will not detect the marker of infection.

Risk is usually described as the estimated residual risk per million donations tested, or up to the estimated number of years of blood donation screening before a potentially infectious donation is not detected. It is not the estimated risk of transmission, since transmission will also depend on the amount of undetected virus in the component which may vary by type of components transfused. Residual risk is only calculated for for HBV, , HCV and  and HIV.

Each year the unitunit calculate calculate residual risk for the UK based on surveillance data for the previous 3 years.

View See the latestlatest Estimated residual risk estimatesfor HBV, HCV and HIV.

Bacterial screening of platelets

The transfusion of a platelet or red cell pack contaminated with bacteria may result in a a TTI in in the recipient. The frequency of confirmed bacterial bacterial TTIs is is greater in platelet transfusions because these packs are stored at 22°C, which provides favourable conditions for bacterial growth.

A bacterial screening surveillance programme was also introduced to collect data on the number of positive results in England and north Wales over time, and by centre.

Bacterial screening is carried out using the BacT/ALERT system. MoreFurther details on the method of screening isare available in the ‘Data sources and methods’ documents for each year of ‘Safe supplies’,supplies’ in the NHSBT and UKHSA Epidemiology Unit’s annual report. All initially reactive samples are sent to the nationalNHSBT bacteriology laboratory for testing, and further investigations of the donor may be carried out following receipt of these results.

Platelet donation

A platelet donation may be made either by:

• apheresis, where one component donor can donate up to 3 platelet packs
• pooling platelets from whole blood donors, where 4 donors contribute to 1one pooled platelet pack

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TMER

The Chair of the Standing Advisory Committee on Transfusion MedicineTransmitted EpidemiologyInfections Review(SACTTI) may (TMER)also isreceive aearly collaborativewarning projectcommunications betweenfrom other organisations such as the UKEuropean NCJDRSUBlood Alliance which are also incorporated into the EIR. andThe EIR are reviewed by the UK Blood Services.Service TheSACTTI. mainAny purposeactions isare flagged with the relevant blood service committee and may lead to investigatefurther whetherrisk thereassessment, ischanges anyto evidencethe thatdonor CJDselection guidelines, or variantother Creutzfeldt-Jakobblood diseasesafety (vCJD)measures, maywhere havenecessary. beenThe transmittedannotated viaEIR records the blooddecision supply.outcomes and are stored for future audit by JPAC.

ViewFurther more information onis theavailable TMER project.on:

• HTLVUK blood services surveillance and preparedness of emerging infectious agents from JPAC
• UKHSA register

emerging infection surveillance

TMER

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Information on CJD services in Edinburgh, including testing and clinical advice, is available on the University of Edinburgh website.

HTLV register

Donors with HTLV and HTLV specialist clinic attenders are invited to participate in the HTLV National Register. The HTLV National Register is a jointcollaboration project between UKHSA, NHSBT and Imperial College Londonin NHSLondon. Trust.It is the first prospective study of its kind in Europe.

Donor surveys

ViewThe moreunit informationran large donor surveys in 2014 and 2025 looking at HTLV:behaviour nationalrelating registerto donor selection policy, and donor travel surveys in 2016. and 2025 looking at travel patterns.