HPR volume 15 issue 13: news (4 August)
Updated 19 January 2022
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Transfusion transmitted infections (UK): 2020
Transfusion transmitted infections (TTIs) remain rare in the UK due to donor selection criteria and rigorous testing of blood donations. All suspected TTIs reported to the blood services are investigated.
During 2020, the UK Blood Services investigated 135 suspected bacterial cases and 5 suspected viral incidents.
From these suspected cases, there have been:
- one bacterial near miss (Staphylococcus aureus): a bacterial infection was found in a unit for donation, but it did not get transfused to a recipient
- one probable transfusion-transmitted hepatitis B virus (HBV): although HBV DNA was detected in a donor sample, it could not be sequenced due to a very low viral load and hence this is reported as probable transmission
- one probable transfusion-transmitted hepatitis E virus (HEV) incident that was finalised in 2020, but reported in 2019
The bacterial near miss was investigated after a hospital returned an abnormal looking apheresis platelet pack to the labs before it was transfused. Bacterial screening and cultures from this pack identified Staphylococcus aureus, which was also isolated from the donor. Molecular typing confirmed that this isolate was the same as that in the pack and therefore represented a single strain. The donor was informed and removed from the donor panel. This near miss is 1 of 10 bacterial near misses reported since 2011.
The 4 UK Blood Services all use the BacT/ALERT system for bacterial screening which has been successful in reducing the risk of bacterial TTIs. The last confirmed bacterial transfusion transmitted infection (TTI), a Staphylococcus aureus, was reported in 2015.
The probable HBV case was an asymptomatic infection, identified via routine dialysis screening, in a patient with significant underlying health issues. No other source or risk factors for the infection were identified, except that the patient was born in a part of the world where HBV is endemic. Sequencing was carried out on the recipient sample but, although HBV DNA was detected in the donor sample, the viral load was too low to allow sequencing to confirm this transmission. The recipient sample was found to have the HBV genotype commonly identified in Sub-Saharan Africa. It was concluded that this patient probably acquired the HBV infection via a blood transfusion in 2019.
The 2019 investigation of the probable HEV transmission was concluded in 2020. The recipient was diagnosed with an HEV infection even though they had not developed hepatitis. HEV RNA was not detectable by the initial screening and sequencing could not be done due to the low viral load. This case has been finalised as a probable TTI. HEV infections are generally acquired through food, and there is no specific donor selection to minimise donations from those infected.
A number of strategies are in place to reduce the risk of viral TTIs, including donor selection criteria and testing, and surveillance is in place to monitor the impact.
More information on these cases is available in the Serious Hazards of Transfusion (SHOT) 2020 Annual Report.
Key messages from the new SHOT report are as follows.
- The risks of a potentially infectious HBV, hepatitis C virus (HCV) or human immunodeficiency virus (HIV) donation not being detected (due to the window period) in the UK are less than 1 per million donations tested. Nevertheless, to maintain haemovigilance, investigations are performed if a recipient is suspected to have been infected via transfusion.
- Bacterial screening of platelets will significantly reduce but not remove the risk of transfusion transmission of bacteria.
Further information about UK TTI surveillance is available from the joint NHS Blood and Transplant (NHSBT) and Public Health England (PHE) Epidemiology Unit: epidemiology@nhsbt.nhs.uk
Infection reports in this issue
Acquired carbapenemase-producing Gram-negative bacteria (England): October 2020 to March 2021.
Sentinel surveillance of blood borne virus testing (England): 2020.
Tetanus in England: 2020.