About 10 years ago I had infectious mononucleosis. If I were to come in contact with it again, could I catch mono again?

Natasha

Infectious mononucleosis (mono) is caused by the Epstein-Barr virus (EBV). In most cases, especially if contracted in early childhood, the infection causes no symptoms. When it does, patients generally experience fever, sore throat, lymph node swelling and changes in their blood cell counts. Symptoms usually resolve within four to eight weeks, but the acute symptoms, including fever, are usually gone much sooner.

When a viral infection occurs, the body makes antibodies (disease-fighting proteins) that are specifically designed to target the virus. Antibodies bind to a specific pathogen (disease-causing microbe), initiating the immune system response to fight the infection. With most viral infections, the infection is eradicated, and the person remains immune for life. This is the case with, for example, hepatitis A (an infection typically caused by contaminated food and water, which causes liver inflammation) and rhinovirus (the cause of the common cold). Unfortunately, there are many different strains of rhinovirus, and the antibody response only protects the patient from the exact strain that caused the initial infection. Because of this, people can continue to get more colds, each one caused by a different strain of rhinovirus.

The case of EBV is a little different. The body makes anti-EBV antibodies, but the infection is not entirely eradicated. The virus "hides out" in certain white blood cells and in the lining of the throat and salivary glands. Sometimes, especially when the immune system is weakened, as occurs after organ transplantation, EBV infection can reactivate and cause disease. The anti-EBV antibodies do protect against repeat acute infection with EBV, however, so once you have had mono, you should not develop it again if you are exposed to someone with the illness.

This same process occurs with another viral infection, chickenpox (varicella). A person who has had chickenpox is essentially immune to future bouts of chickenpox. However, the varicella virus is not eradicated from the body and can reactivate in the future, causing shingles.