What Is the Risk of HIV from a Blood Transfusion?

Odds Equivalent to That of Being Struck by Lightning

Pouches of donated blood in hospital
Pouches of donated blood in hospital. Getty Images/ERproductions Ltd/Blend Images

Blood transfusions are vital at times of medical emergency, yet many people remain concerned about the risks of contracting infectious diseases, like HIV, through tainted blood. While many of those fears have died down since height of the AIDS crisis in the 1980s—when people like Ryan White and Elizabeth Glaser drew worldwide attention after having acquired HIV from a blood transfusion—there are still those who doubt the veracity of universal screening technologies.

And how could they not, considering the decades-long ban on gay blood donations? After all, it's difficult for someone to trust a technology if public health officials express doubts themselves, tacitly or otherwise.

Today, universal blood screenings are routine performed in nearly 75% of countries worldwide. The high-sensitivity tests not only screen for HIV but a plethora of other transmittable infections including hepatitis B and hepatitis C.

Blood Transfusion Risk In the U.S.

According to data from the Centers for Disease Control and Prevention (CDC), the risk of getting HIV from a blood transfusion in U.S. is extremely low, approximately one chance out of every 2,000,000 units of blood.

To put that into better perspective, that's roughly the same odds as getting struck by lighting or naturally conceiving identical twins.

Today, over 14 million transfusions are performed in the U.S. each year.

All donors are routinely pre-screened, using a questionnaire to assess whether they are at high risk for transmittable diseases. (Injecting drug users, for example, are actively banned due to high rates of hepatitis C, while gay men are similarly banned if they have had sex anytime in the past year.)

Thereafter, each unit of blood is screened using a standard panel of high-sensitivity tests. These include tests for:

  • HIV
  • Hepatitis B
  • Hepatitis C
  • Bacterial contamination
  • HTLV (human T-lymphotropic virus) types I and II)
  • Syphilis
  • West Nile Virus

Improvements in HIV Testing Technologies

Nearly everyone in the U.S. who had been infected with HIV as the result of a blood transfusion received them before March 1985, the year during which the HIV antibody testing was first approved.

The one problem with the early tests is that they were sometimes unable to detect antibodies if a person donated blood within the so-called "window period"—roughly 22 days after exposure. By 1996, the U.S. Food and Drug Administration were able to shore up this gap by implementing faster HIV p24 antigen tests, the results of which were further improved in 1999 with the introduction of the nucleic acid amplification test (NAT).

Newer-generation combination antigen/antibody tests have even better sensitivity/specificity.

How Safe Is Blood in Other Countries?

According to the World Health Organization,25 countries do not routinely screen their blood supplies for one or more of the above-listed infections.

Among them, countries like Egypt today have the highest rate of hepatitis C in the world, which is passed not only through the blood supply but as a result of non-sterile medical procedures, reused syringes and hypodermic needles, and routine vaccinations, Tattooing and even everyday grooming services like straight razor shaving are considered risk among Egyptians, who have a reported one-in-five risk of contracting hepatitis C.

Edited by Dennis Sifris, MD and James Myhre


Centers for Disease Control and Prevention. "Blood Safety Basic." Atlanta, Georgia; accessed September 29, 2015. 

CDC. "HIV Transmission Risk." Accessed September 29, 2015. 

CDC. "HIV Transmission Through Transfusion -- Missouri and Colorado, 2008." Morbidity and Mortality Weekly Report. October 22, 2010 / 59(41);1335-1339.

HIVInSite/University of California, San Francisco. "Transmission of HIV by Blood, Blood Products, Tissue Transplantation, and Artificial Insemination."San Francisco, California; accessed September 29, 2015. 

World Health Organization. "Global Hepatitis Programme: Guideline development for Hepatitis C virus Screening, Care and Treatment in low and middle income countries." Geneva, Switzerland; 2014; published online.

Continue Reading