Blood, tissue and organ donors: surveillance schemes
The NHSBT and UKHSA surveillance programme is a series of national schemes that monitors infections in blood, tissue and organ donors, and transfusion recipients.
NHS Blood and Transplant (NHSBT) 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 NHSBT 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 is collated and analysed by the unit to produce surveillance reports and inform and evaluate policy changes relating to infection risk. These reports 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 HIV window period donation
- outcome of investigations into suspected post-transfusion infections
NHSBT and UKHSA surveillance programme
The NHSBT and UKHSA surveillance programme is a series of national schemes managed by the unit, including:
- infections in blood donors: monitored through the surveillance of donations tested and the collection of information about infected donors identified
- infections in living surgical bone and deceased tissue donors (for NHSBT): monitored in a similar way to blood donors
- infections in deceased organ donors: monitored in a similar way to blood donors
- reported post-transfusion infections: monitoring investigations among transfusion recipients and forms part 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
- Transfusion Medicine Epidemiology Review (TMER) in partnership with the National CJD Research and Surveillance Unit (NCJDRSU) in Edinburgh: a study which aims to look for evidence of transfusion transmission of Creutzfeldt-Jakob disease (CJD)
The following UK and Irish blood services contribute data, which is used to assess and improve blood and tissue safety:
- NHSBT
- 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:
- HBV
- HCV
- hepatitis E 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 T-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 Professional Advisory Committee (JPAC) guidelines for the UK Blood and Tissue Services.
Surveillance of infections among tissue donors
NHSBT 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, NHSBT runs the NHS cord blood bank. All tissue donors (including cord blood donors) are routinely tested for markers of:
- HBV
- HCV
- HIV
- HTLV infection
- treponemal infections (like syphilis)
Surveillance of transfusion transmitted infection (TTI)
Transfusion transmitted infection due to viruses or parasites is very rare. A newly identified viral infection in a blood transfusion recipient with no other apparent risk may indicate a transfusion-transmission. The year of transfusion may be many years before the year in which the incident is investigated and/or reported to SHOT due to the chronic nature, and possible late recognition of some viral infections.
A TTI investigation will only commence once the infection status of the recipient has been clarified.
Guidance on reporting of suspected transfusion transmitted infection is available on NHSBT’s Hospitals and Science: Reporting adverse events.
TTI definition
A report of an infection suspected to be due to transfusion is classified as a TTI, following investigation, if:
- the recipient had evidence of infection post transfusion, 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 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’ 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 HBV, HCV and HIV.
Each year the unit calculate residual risk for the UK based on surveillance data for the previous 3 years. See the latest Estimated residual risk for HBV, HCV and HIV.
Bacterial screening of platelets
The transfusion of a platelet or red cell pack contaminated with bacteria may result in a TTI in the recipient. The frequency of confirmed bacterial TTIs 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. Further details on the method of screening are available in the ‘Data sources and methods’ documents for each year of ‘Safe supplies’ in the NHSBT and UKHSA Epidemiology Unit’s annual report. All initially reactive samples are sent to the NHSBT 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 one pooled platelet pack
Emerging infections: horizon scanning
The joint NHSBT and UKHSA epidemiology unit collaborates closely with UKHSA to provide infection horizon scanning for the UK blood services.
The epidemiology unit produces a monthly Emerging Infections Report (EIR), which is described in the position statement Surveillance: preparedness for emerging infectious agents. EIR is a horizon-scanning list of global outbreaks, emerging and re-emerging infections with the potential to affect the UK blood and tissue supply, such as arboviruses or other pathogens with the potential for asymptomatic but viraemic blood donors, or outbreaks with the potential to reduce availability of donors.
The epidemiology unit scans daily and weekly UKHSA reports and other information from credible sources such as European Centre for Disease Control (ECDC) and scientific journals against the Geographical Disease Risk Index. Urgent items are escalated for review without delay while emerging situations may be tracked by more frequent reporting as needed.
The Chair of the Standing Advisory Committee on Transfusion Transmitted Infections (SACTTI) may also receive early warning communications from other organisations such as the European Blood Alliance which are also incorporated into the EIR. The EIR are reviewed by the UK Blood Service SACTTI. Any actions are flagged with the relevant blood service committee and may lead to further risk assessment, changes to the donor selection guidelines, or other blood safety measures, where necessary. The annotated EIR records the decision outcomes and are stored for future audit by JPAC.
Further information is available on:
- UK blood services surveillance and preparedness of emerging infectious agents from JPAC
- UKHSA emerging infection surveillance
TMER
TMER was a collaborative project between the NCJDRSU in Edinburgh and the UK blood services, funded by Department of Health and Social Care between 1997 and March 2025. TMER linked information over time on donors and recipients to look for evidence of CJD transfusion-transmission. TMER identified 3 clinical and 1 asymptomatic case of transfusion-transmitted variant CJD all occurring prior to leucodepletion safety mitigation in 1999. To date there is no evidence for transfusion-transmitted sporadic CJD. CJD was made a notifiable disease in 2025.
The unit will continue to coordinate lookback for CJD cases notified to the Unit via UKHSA.
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 collaboration between UKHSA, NHSBT and Imperial College in London. It is the first prospective study of its kind in Europe.
Donor surveys
The unit ran large donor surveys in 2014 and 2025 looking at behaviour relating to donor selection policy, and donor travel surveys in 2016 and 2025 looking at travel patterns.
Updates to this page
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Updated information on the NHSBT and UKHSA surveillance programme.
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Added HTLV Register section.
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Updated information on HTLV testing and blood transfusions.
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First published.