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Why Blood Donations are Tested for Cytomegalovirus (CMV)

Dan Eberts March 16, 2021

According to the Centers for Disease Control and Prevention, “Cytomegalovirus (pronounced sy-toe-MEG-a-low-vy-rus), or CMV, is a common virus that infects people of all ages.  Over half of adults have been infected with CMV by age 40."  Most people infected with CMV may not show signs or symptoms and not even know they have the virus. 

Healthy people who are infected with CMV usually do not require medical treatment. However, as stated in, “Once a person has the infection, the virus stays in the body, lying dormant (not active).  It can become ‘reactivated’ (come back) weeks or years later.   In people with very weakened immune systems, the reactivated virus may cause serious illness.  Most people, though, will not get symptoms of CMV again.”

Because Cytomegalovirus is spread by bodily fluids and can therefore be transmitted in blood transfusions, all OneBlood donors are tested to see if they are positive or negative for CMV. 

This additional test for CMV is just one more layer of safety for immunocompromised blood recipients. These results are posted in the Donor Profile of our internal records but are not listed in the donor’s online portal.  

So, if you are curious as to whether you are positive or negative for CMV, please ask us next time you register at one of our Donor Centers or Big Red Buses to donate blood.   

Since most adults are already positive for this virus, they can receive blood transfusions from other positive CMV donors.  However, for newborns and patients who have weakened immune systems, CMV negative blood products are required.

The Mayo Clinic reports, “Women who develop an active CMV infection during pregnancy can pass the virus to their babies, who might then experience symptoms.  For people who have weakened immune systems, especially people who have had an organ, stem cell or bone marrow transplant, CMV infection can be fatal.”

 For patient safety, all the blood donations are first cross-matched in the hospital’s laboratories, prior to transfusion, with the intended patient recipient’s blood to assure compatibility.   There are many factors that go into determining the most compatible products for transfusion.  

 It's estimated that between 50 and 80 percent of adults in the United States have CMV by age 40, consider yourself in the minority if you test negative.  At the same time, do not be concerned if later you test positive for it, since it has little effect on most healthy people and does not prevent you from donating blood.  

Proactively testing for the presence of the Cytomegalovirus in donors helps to make transfusions even safer for those with higher risk factors who require CMV negative blood.  Regardless of whether a donor is positive or negative for CMV, their gifts of blood, platelets or plasma can help to save or sustain the lives of patients and their families.

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