Yes, and here’s why.

All of us have bacteria and viruses that live in our bodies for most or all of our lives. The Epstein-Barr virus is one example. It is an extremely widespread virus; the majority of adults across the world are permanently infected with it. Nearly 90% of people in the United States are infected with the virus by age 20.

The virus is often present in our saliva. Most of the time, the virus is passed from one person to another by exposure to saliva, such as during kissing or possibly by exposure to someone’s cough.

Having an infection does not mean that the infection will cause an illness. Epstein-Barr virus can cause a variety of diseases, the most common of which is infectious mononucleosis (often called "mono"), but it lives quietly inside most people for their entire lives without causing any disease. It lives inside white blood cells called lymphocytes, and inside cells that line the throat.

So if you donate a unit of blood, there is a 90% chance the virus will be living in a few of your white blood cells when your blood is given to someone else. But if the person receiving your blood is an adult, there is a 90% chance that he or she already has the virus. So far as we know, any of your virus that is passed to someone else does them no harm. Because blood transfusions containing Epstein-Barr virus have been given for nearly 100 years, we would probably know by now if there were a risk.