Diseases and Organisms

lab worker growing bacteria

The U.S. blood supply is safer than it has ever been. However, any blood borne pathogen has the potential to be transmitted by blood transfusion.

Transfusion-transmitted infections (TTIs) are infections resulting from the introduction of a pathogen into a person through blood transfusion. A wide variety of organisms, including bacteria, viruses, prions, and parasites can be transmitted through blood transfusions.

The use of a standard donor screening questionnaire as well as laboratory tests help to reduce the risk of an infectious organism being transmitted by blood transfusion.

Additionally, the introduction of pathogen reduction technology (PRT) pdf icon[PDF – 6 pages]external icon may help to further reduce the risk of TTIs. PRT involves treating certain blood products with a pathogen-inactivating agent soon after collection. The use of PRT can not only limit the number of TTIs but may also eliminate the need for irradiation to prevent transfusion-associated graft-vs-host diseases (TA-GVHD) and serologic testing for cytomegalovirus (CMV) for at-risk patients. Currently, this technology is approved for apheresis platelets and plasma products.

Bacterial Contamination of Blood Products

Bacterial contamination of blood products, especially in platelets that are stored at room temperature, is the most common infectious risk of blood transfusion, occurring in approximately 1 of 2000-3000 platelet transfusions (Fuller, 2009; Hong, 2016). Transfusion–transmitted sepsis, while less common, can cause severe illness and death. Improved donor screening as well as improved methods of collection, handling, and storing of blood products has decreased bacterial contamination in recent years.

  • Gram–positive bacteria

    Gram-positive bacteria normally found on the skin, such as Staphylococcus epidermidis or Staphylococcus aureus, are the most common bacterial contaminants of blood products. This type of contamination is thought to occur when the bacteria on the skin is passed into the collected blood through the collection needle.

  • Gram-negative bacteria

    Gram-negative bacteria are part of normal flora in the gastrointestinal tract (intestines). This type of contamination is thought to occur when blood is collected from donors who have bacteria in the bloodstream but without symptoms. Examples include Acinetobacter, Klebsiella, and Escherichia coli (E. coli). Some gram-negative bacteria are resistant to multiple drugs and are increasingly resistant to many available antibiotics.

  • Anaplasmosis

    Anaplasmosis is a tick-borne disease caused by the bacterium Anaplasma phagocytophilum. It is transmitted to humans by tick bites primarily from the black-legged tick and the western black-legged tick, and can be transmitted via blood product from an infected donor (Jereb, 2012). Symptoms of anaplasmosis include fever, headache, chills, and muscle aches.

  • Brucellosis

    Brucellosis is a disease caused by bacteria from the Brucella species, which is transmitted to humans from contact with infected animals such as sheep, cattle, and dogs. Brucellosis has been previously described to be transmissible via blood product from an infected donor (Econmidou, 1976). Symptoms include fever, sweats, headache, and fatigue.

  • Ehrlichiosis

    Ehrlichiosis is a group of tick-borne diseases caused by bacteria in the Ehrlichia species. It is transmitted to humans mainly from the lone star tick and the blacklegged tick. Transmission via blood product from an infected donor has previously been documented (Regan, 2013). Symptoms include fever, chills, headache, and muscle ache.


Economidou J, Kalafatas P, Vatopoulou T, Petropoulou D, Kattamis C. Brucellosis in two thalassaemic patients infected by blood transfusions from the same donor. Acta Haematol. 1976;55:244–249. doi:10.1159/000208021. PMID: 816164.

Fuller, A. K., Uglik, K. M., Savage, W. J., Ness, P. M., & King, K. E. (2009). Bacterial culture reduces but does not eliminate the risk of septic transfusion reactions to single-donor platelets. Transfusion, 49(12), 2588-93.

Hong, H., Xiao, W., Lazarus, H. M., Good, C. E., Maitta, R. W., & Jacobs, M. R. (2016). Detection of septic transfusion reactions to platelet transfusions by active and passive surveillance. Blood, 127(4), 496-502. Accessed November 04, 2018. https://doi.org/10.1182/blood-2015-07-655944external icon.

Jereb M, Pecaver B, Tomazic J, et al. Severe human granulocytic anaplasmosis transmitted by blood transfusion. Emerg Infect Dis. 2012;18(8):1354-7.

Regan J, Matthias J, Green-Murphy A, Stanek D, Bertholf M, Pritt BS, Sloan LM, Kelly AJ, Singleton J, McQuiston JH, Hocevar SN, Whittle J. A Confirmed Ehrlichia ewingii Infection Likely Acquired Through Platelet Transfusion, Clinical Infectious Diseases, Volume 56, Issue 12, 15 June 2013, Pages e105–107, https://doi.org/10.1093/cid/cit177external icon

Parasitic Diseases

Transmission of parasitic infections through blood donation is rare. To help minimize the risk of transfusion-transmitted illnesses, including parasitic infections, donors are asked questions to assist in determining if they are in good health. To reduce the risk of transmitting specific infections (e.g., malaria), donors are asked about recent travel to areas where some infections are more common.

Examples of parasitic diseases that can be transmitted by blood transfusion are listed below.

  • Babesiosis

    Babesiosis is caused by microscopic parasites that infect red blood cells and are spread by certain ticks. In the United States, tick-borne transmission is most common in particular regions and seasons: it mainly occurs in parts of the Northeast and upper Midwest and usually peaks during the warm months.

  • Chagas Disease

    Chagas disease is caused by the parasite Trypanosoma cruzi, which is transmitted to animals and people by insects. Trypanosoma cruzi is found only in the Americas, and transmission of the parasite occurs mainly in rural areas of Latin America where poverty is widespread. Since 2007, first time blood donors have been screened for antibodies to T. cruzi  in the U.S., making the risk of transfusion-transmitted Trypanosoma cruzi extremely rare.

  • Leishmaniasis

    Leishmaniasis includes two major diseases, cutaneous leishmaniasis and visceral leishmaniasis, caused by more than 20 different leishmanial species. Leishmaniasis is transmitted by the bite of small insects called sand flies. The distribution of leishmaniasis is world-wide. Several transfusion-transmitted cases of visceral form of the Leishmania have been reported.

  • Malaria

    Malaria is a serious and sometimes fatal disease caused by a parasite that commonly infects a certain type of mosquito which feeds on humans. People who get malaria are typically very sick with high fevers, shaking chills, and flu-like illness. About 1,700 cases of malaria are diagnosed in the United States each year. The vast majority of cases in the United States are in travelers and immigrants returning from countries where malaria transmission occurs, many from sub-Saharan Africa and South Asia.

Viral Diseases

Like bacteria and parasites, viruses that are blood-borne can be transmitted by blood transfusion. Donors are asked questions about their social behavior and health history to help minimize the risk of transfusion-transmitted viral diseases.

Examples of viral diseases that can be transmitted through transfusion are listed below.

  • Chikungunya Virus

    Chikungunya Virus (ChikV) is an arbovirus spread to humans from mosquitos. ChikV outbreaks have occurred in Africa, Asia, Europe, the Indian and Pacific Oceans, and the Caribbean. No ChikV outbreaks have been reported in the United States. Symptoms include fever and joint pain, and there is no vaccine or medicine to prevent or treat ChikV.

  • Dengue Fever

    Dengue fever (DF) is caused by any one of four related viruses transmitted by the mosquitoes. With more than one-third of the world’s population living in areas at risk for transmission, dengue infection is a leading cause of illness and death in the tropics and subtropics. As many as 100 million people are infected yearly.

  • Hepatitis A Virus

    Hepatitis A is a contagious liver disease that results from infection with the Hepatitis A virus (HAV). Hepatitis A is spread primarily by the fecal-oral route, but transfusion-transmitted HAV infection has been reported. Hepatitis A can range in severity from a mild illness lasting a few weeks to a severe illness lasting several months, and in rare occasions can cause death.

  • Hepatitis B Virus

    Hepatitis B is a contagious liver disease caused by the Hepatitis B virus (HBV). 1.2 million Americans are living with chronic Hepatitis B, most are unaware of their infection. Over time, approximately 15%–25% of people with chronic Hepatitis B develop serious liver problems, including liver damage, cirrhosis, liver failure, and liver cancer. Every year, approximately 3,000 people in the United States and more than 600,000 people worldwide die from Hepatitis B-related liver disease. Since 1972, the blood supply has been screened for Hepatitis B in the U.S., making the risk of transfusion-transmitted HBV extremely rare.

  • Hepatitis C Virus

    Hepatitis C is a contagious liver disease caused by the Hepatitis C virus (HCV). Hepatitis C is the most common chronic bloodborne infection in the United States. 3.2 million Americans are living with chronic Hepatitis C, most are unaware of their infection. Chronic Hepatitis C is a serious disease that can result in long-term health problems, including liver damage, cirrhosis, liver failure, and liver cancer. Since 1992, the blood supply has been screened for Hepatitis C in the U.S., making the risk of transfusion-transmitted HCV extremely rare.

  • Hepatitis E Virus

    Hepatitis E is a contagious liver disease caused by the Hepatitis E Virus (HEV). HEV is transmitted via the fecal-oral route, generally though contaminated water in areas with poor sanitation. Though HEV is rare in the United States, it is more common in other countries. Hepatitis E-related lived disease is self-limiting and does not lead to chronic infection.

  • Human Immunodeficiency Virus (HIV)

    HIV is the cause of acquired immune deficiency syndrome, or AIDS. CDC estimates that about 38,500 people in the United States contracted HIV in 2015. This risk of transfusion-transmitted HIV is extremely remote due to the rigorous testing of the U.S. blood supply.

  • Human T-Cell Lymphotrophic Virus (HTLV)

    HTLV is a viral infection prevalent in Japan, sub-Saharan Africa, the Caribbean Islands and South America. HTLV can be spread mother to child, through sexual contact, or via infected blood products. Though many infected remain asymptomatic, HTLV can lead to neoplastic diseases, inflammatory syndromes, and opportunistic infections.

  • West Nile Virus

    West Nile virus (WNV) is a potentially serious illness. Experts believe WNV is established as a seasonal epidemic in North America that flares up in the summer and continues into the fall. Symptoms of the illness is include fever, headache, tiredness, aches, and sometimes rash. Although WNV is most often transmitted by the bite of infected mosquitoes, the virus can also be transmitted through contact with infected animals, their blood, or other tissues. Also see West Nile Virus Transfusion: Questions and Answers.

  • Zika Virus

    Zika Virus (ZIKV) is a mosquito-borne arbovirus spread by the Aedes species mosquito. ZIKV can be passed from a pregnant woman to her fetus, and infection during pregnancy can lead to serious birth defects. Symptoms of Zika include fever, rash, headache, joint pain, red eyes, and muscle pain. Transfusion transmitted cases of ZIKV have been reported.

Prion Diseases

Prion Diseases, or transmissible spongiform encephalopathies (TSEs), are a family of rare, progressive neurodegenerative disorders that affect both humans and animals. The causative agent of TSEs is believed to be a prion. A prion is an abnormal, transmissible agent that is able to induce abnormal folding of normal cellular prion proteins in the brain, leading to brain damage and the characteristics signs and symptoms of the disease. Prion diseases are usually rapidly progressive and always fatal. Like viruses, bacteria, and parasites, prions are bloodborne and may be transmitted by blood transfusion.

  • Variant Creutzfeldt-Jakob Disease (vCJD)

    Variant Creutzfeldt-Jakob Disease (vCJD) is a rare, rapidly progressing neurological disease that causes dementia and death. In 1996, cases of this variant form of Creutzfeldt-Jakob Disease (vCJD) were first reported in the United Kingdom.

    Transmission of vCJD in the United Kingdom has been thought to be related to transfusions received years earlier with non-leukoreduced red blood cells from healthy donors who became ill with vCJD months to less than 4 years after the donations. Recipients of blood components from other donors later diagnosed with vCJD remain under surveillance in the United Kingdom and France. The magnitude of the risk of acquiring vCJD from transfusion is uncertain.