Number of recipients with confirmed/probable Transfusion-Transmitted Infections (TTI)

Definition:

If following investigation, 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.

Number of recipients with confirmed TTI, by year of transfusion, and infection in the UK

Number of recipients with probable TTI, by year of transfusion, and infection in the UK

The risk of a TTI in the UK is extremely low. Around 130 suspected transmissions are investigated in the UK each year, a small number are concluded as confirmed TTIs. The last confirmed bacterial TTI was in 2015. In 2022, the first confirmed transmission of hepatitis B from a donor with occult hepatitis B was confirmed by DNA sequencing in the UK. The transmission involved two recipients and the transfusions occurred in 2021. The year of transfusion may be many years before the year in which the incident is investigated and reported to SHOT due to the chronic nature, and possible late recognition, of some viral infections.

Please note – the numbers in this figure may differ from the numbers reported in the individual Annual SHOT Report chapters. This is due to the fact that some investigations take many months to complete, or infections discovered at a later date. Cases are included here based on the year of transfusion, not the year it was reported/confirmed.

The probable HEV and HBV transmissions could not be confirmed due to the levels of RNA and DNA being too low for molecular typing. For the probable bacterial transmission it was not possible to ascertain that the source was the donor.

Timeline of Risk-Reduction Strategies and Transfusion-Transmitted Infections

Recent Key Messages (prior to 2024)

It is important that any suspected TTI is reported to allow investigation, however, it should be noted that confirmed or probable TTI are rare

Suspected TTI should be discussed with the consultant microbiologist, virologist and/or other infection diseases expert to confirm the diagnosis and following that, reported to the appropriate UK Blood Service for further investigations

The UK Blood Services store a sample from every blood donation for at least three years. Testing can be done on these samples during this time if a TTI is suspected

It is important that all healthcare professionals consenting patients for blood transfusion have up-to-date knowledge of blood donation testing, and the extremely small but potential risk of routine testing not detecting an infection in a donor that may enter the blood supply. For acute HBV, HCV, and HIV infections this has been estimated to be less than 1 in 1 million donations tested and confirmed and probable transmissions remain rare with very few numbers each year

The UK Blood Services continue to monitor rates of infection in donors to sustain a safe supply of blood components

SHOT data is used to inform policy and change it when necessary. Additional hepatitis B anticore testing has been introduced to reduce the risk of hepatitis B transmission from donors with occult hepatitis B where viral levels may be below the level of detection by the previous routine screening assays

TTI Resources

Please also see the Transfusion-Transmitted Infections Webinar 2020

This short video that has been developed with the NHSBT Microbiology team covers how the safety of the blood supply in the UK is monitored and provides an overview of the measures in place to ensure safety. Video released May 2024.

Monitoring the safety of the blood supply

TTI Case Studies

TTI Figures

SHOT Bite No. 7: TTI (2016)

TTI Annual Report Chapters

To access the chapter click either on the cover of the Annual SHOT Report or the link below the picture