Blood and blood products transfusion can be life saving, but if not done appropriately and with appropriate precaution, blood transfusion can also cause problem to the recipient of the transfused blood. The complications that can occur due to blood transfusion includes, transmission of infectious agent (from donor to recipient), immunologically mediated adverse reactions (such as hemolysis, graft-versus-host reaction, anaphylactic reaction etc.), non-immunologically mediated adverse reactions such as hypothermia, fluid overload, electrolyte excess etc.

There are several infectious agents that can be transmitted through blood transfusion, but practically very rarely seen in clinical practice due to rigorous screening of blood for infectious agents before transfusion, as well as by selecting blood donors with caution, before collecting from blood donors. The infectious agents that can be transmitted through blood transfusion may be virus, bacteria and other infectious agents, such as malarial parasites. Among these infectious agents, viruses are most important in blood transfusions and should be screened for carefully.

What viruses can be transmitted through blood transfusion?

The viruses that can be transmitted through blood transfusion are HIV Type-1, hepatitis-B, hepatitis-C and other hepatitis viruses, cytomegalovirus, West Nile virus, Parvovirus B-19, HTLV type-I (human T cell lymphotropic virus) etc.Viral infection through blood transfusion in becoming increasingly rare, due to improved screening and testing.

HIV Type-1:

The most important virus that can be transmitted through blood transfusion is HIV type-1. Donor’s blood is routinely tested in the blood banks across the world for antibodies to HIV-1, HIV-1 p24 antigen, and HIV RNA using Nucleic acid amplification testing (NAT). Despite rigorous testing standards the risk of HIV-1 infection is still present and occurs in approximately 1 in 2 million units of blood transfusions. This is due to collection of blood from donors during window period (“window period” is first few weeks after contacting HIV, when infection is present but can not be detected by any laboratory tests). Transmission of HIV Type-2 can also occur, although now extremely rare, e.g. there is no report of HIV Type-2 transmission in USA since 1992, through blood transfusion.

Hepatitis-B:

It is the most commonly transmitted infection through blood transfusion. The risk of transfusion-associated HBV (hepatitis-B virus) infection is 1 in 63,000 units of blood transfusions, which is more than twenty folds higher than other infections like HIV, and hepatitis-C. Donor’s blood is routinely tested for HbsAg (hepatitis B surface antigen) and not by Nucleic acid amplification testing, due to low level of virus in blood. Hepatitis-B can be prevented among recipients of blood, especially in those who receive long term transfusion, by vaccination with hepatitis-B.

Hepatitis-C:

The risk of transmission of Hepatitis-C is rare due to testing of blood donations for HCV (Hepatitis-C virus) as well as for HCV RNA and occurs in approximately 1 in 2 million units of blood transfusions. The Hepatitis-C infection occurring through blood transfusion may be asymptomatic, but it may lead to active hepatitis, liver failure or cirrhosis.

Cytomegalovirus:

It is vary common virus, which infects approximately half of the population and is transmitted along with infected white blood cells (WBC) during blood transfusion. The few WBCs which may be present in platelet concentrates may also transmit cytomegalovirus. The risk of cytomegalovirus transmission is reduced if WBCs are removed from blood.

West Nile virus:

The transmission of West Nile virus through blood transfusion was first recorded in the year 2002 and since 2003 in many blood banks the test (it is detected by Nucleic acid amplification testing) is done routinely. The West Nile virus, which is transmitted through blood transfusion can cause asymptomatic infection or it may be fatal, the risk of severe infection being high among elderly population.

Parvovirus B-19:

The virus causes “fifth disease” or erythema infectiosum among children and transmitted through pooled plasma or other blood components.

HTLV (human T cell lymphotropic virus) type-I:

The risk of transmission of HTLV type-I & II is approximately 1 in 650,000 units. Tests for detection of HTLV type-I & II are done routinely. HTLV type-I can cause adult T-cell leukemia/lymphoma and rarely tropical spastic paraparesis, but HTLV type-II is not associated with any disease.

What bacteria can be transmitted through blood transfusion?

The bacteria (mostly gram-negative bacteria) that can be transmitted through blood transfusion are Pseudomonas, Yersinia, Serratia, Acinetobacter and Escherichia species, as they can grow at temperature between 1- 6°C (blood is stored at this temperature). The transmission of bacteria through blood transfusion is mainly due to contamination of blood after collection, but transmission of virus through blood transfusion is due to presence of viral disease (the viral disease is generally asymptomatic or during incubation period, which may be of long duration) in the blood donor.

The risk of transmission of bacteria through blood transfusion is much less in compare to virus transmission, but the relative risk of bacterial transmission has increased due to dramatic decrease of risk of virus transmission. The risk of bacterial contamination (transmission) is much less due to the inability of bacteria to grow well at cold temperatures. The Packed Red Blood Cells (PRBC) and fresh-frozen plasma (FFP) are not commonly contaminated by bacteria and not common source of bacterial transmission.

Gram-positive bacteria such as coagulase-negative staphylococci may also be transmitted; especially platelet concentrates, as it is stored at room temperature which can help growth of contaminated bacteria. In fact the risk of contamination of platelet concentrate is quite high with coagulase-negative staphylococci and calculated to be 1 in 1000-2000 single unit platelet. Death rate was also high at 1 in 17,000 single unit platelet transfusions before 2004, the year blood banks started detecting contaminated platelet concentrates. At present the risk is much lower.

If blood contaminated with bacteria is transfused, it may cause fever and chills, which may lead to DIC (disseminated intravascular coagulation) and septic shock. The developments may be sudden in onset (within minutes) or it may occur several hours after transfusion, which is due to presence of endotoxins formed by the contaminated bacteria during storage (at room temperature). If this reaction is suspected (the signs and symptoms of this reaction occurs suddenly and very severe unlike febrile nonhemolytic transfusion reaction, which do not occur abruptly) the transfusion should be stopped immediately and appropriate treatment started with broad spectrum antibiotics and by reversing shock, if present. The bag containing blood component should be sent for culture, antibiotic sensitivity and Gram stain. The blood bank should be informed if there is any clerical error or any serological error.

What other infectious agents are transmitted through blood transfusion?

The infectious agents other than virus and bacteria which can be transmitted through blood transfusion are malarial parasites (the risk of transmission of malaria is 1 in 4 million units of blood transfusions, but may be higher in malaria endemic areas), agents causing diseases such as syphilis (caused by Treponema pallidum), Chagas disease (caused by parasite known as Trypanosoma cruzi), babesiosis, Creutzfeldt-Jakob disease (caused by infectious protein particles known as “prion”), Lyme disease (caused by a spirochete, Borrelia burgdorferi sensu lato) etc. But the incidence of transmission of these agents is extremely rare in appropriate clinical setting.

You can find here about Immune Mediated Adverse Reactions in Blood Transfusion