What is the most common microbial agent transmitted by blood transfusion?

Hepatitis C Virus is the Most Common Microbial Agent Transmitted by Blood Transfusion

The most common microbial agent transmitted by blood transfusion is hepatitis C virus (HCV), which historically accounted for the majority of post-transfusion hepatitis cases. 1

Evidence Supporting HCV as the Most Common Transfusion-Transmitted Agent

• Studies have shown that HCV is the etiologic agent of the majority of parenterally transmitted or bloodborne non-A, non-B hepatitis worldwide 2
• Historical data demonstrated that 90% of post-transfusion hepatitis in the United States was not due to either hepatitis A or B, but rather to what was later identified as HCV 2, 1
• Before effective screening was implemented, incidence rates of HCV (then called non-A, non-B hepatitis) were as high as 21% after blood transfusion 2

Comparison with Other Transfusion-Transmitted Agents

Hepatitis B Virus (HBV)

• By the mid-1970s, improved screening had reduced post-transfusion hepatitis B rates to 0.3%-0.9% per transfusion recipient 2
• Current incidence of post-transfusion hepatitis B is estimated to be around 0.002% per transfusion recipient 2

Human Immunodeficiency Virus (HIV)

• HIV transmission through blood transfusion has been dramatically reduced through donor screening 3
• HIV has never reached the historical prevalence rates of HCV in transfusion recipients

Cytomegalovirus (CMV)

• While CMV is common in the general population (30-50% of adults show evidence of past infection), it is not the most commonly transmitted agent through blood transfusion 4

Evolution of Blood Safety Measures

• The shift from paid to volunteer blood donors substantially reduced the incidence of post-transfusion HCV 2
• Implementation of screening tests has dramatically reduced transmission risks:
  • Anti-HCV antibody screening (initiated in 1990)
  • Nucleic acid testing (NAT) for HCV
  • Surrogate markers like ALT and anti-HBc testing 2, 1

Current Risk Status

• Modern screening has reduced the risk of HCV transmission to approximately 0.001% per unit transfused 2
• Despite these improvements, HCV remains historically the most commonly transmitted viral agent through blood transfusion 1

Clinical Implications

• Patients with abnormal liver function tests after receiving blood products should be tested for HCV and other hepatitis viruses 1
• The implementation of donor screening has virtually eliminated risks for HCV transmission from transplantation 2

While modern blood screening techniques have dramatically reduced the risk of all transfusion-transmitted infections, the historical data clearly shows that hepatitis C virus has been the most common microbial agent transmitted through blood transfusion.