In this post, I will go over the cause of infectious mononucleosis, the symptoms and signs, how it is diagnosed, and then answer the question posed in the heading.
Infectious mononucleosis is often referred to as “mono” for short (also called glandular fever by some), and is caused by the Epstein-Barr virus (EBV). EBV is a member of the herpesvirus family and many people are infected with it in childhood or early adulthood. By the age of 40, more than 95% of persons have already been infected.
Children who get infected with EBV are often asymptomatic, or may have a mild illness with fever, malaise, and poor appetite, lasting only a few days. On the other hand, adults infected with EBV tend to be more symptomatic with fever, sore throat, swollen glands in the neck, abdominal pain (from swelling of the liver and spleen) and extreme fatigue. After EBV infection resolves, the virus is cleared from the blood and tissues of the body. However, it is not eradicated completely, but remains dormant in B-cells indefinitely.
Generally speaking, EBV infection is not life threatening; most affected persons recover without any consequences. However, the fatigue from the infection can be rather prolonged, sometimes lasting months. Persons at risk for serious infection with EBV are those with extremely weakened immune systems such as those undergoing chemotherapy for cancer, those who have had transplants (organ or bone marrow), and persons with untreated AIDS. In these cases, infection can be so severe that it spreads throughout the body causing dysfunction of many organs including the liver and brain.
Diagnosis of mono involves doing several blood tests, including one to check for the presence of antibodies targeting EBV. Because most people had EBV infection in the past, many of these EBV antibodies will show up on the blood test, and, at a glance, it would appear as if the person had a positive result for acute (new) EBV infection. The key in interpreting the test result is knowing which of these antibodies are present only in acute infection and which ones are present only after the infection has long past. Once someone has had mono, the ‘late’ antibodies against EBV will persist in the blood for life. Because the interpretation of the results can be confusing, sometimes we Infectious Diseases specialists are asked to see patients and assist in the diagnosis.
So to answer the question…can you get mono more than once? Recurrence or reactivation of EBV infection is rare. When it occurs it is often in someone with a profoundly weakened immune system. Of note, EBV is not the only germ that can cause a mononucleosis-like syndrome. Other causes include streptococcal pharyngitis (“strep throat”), acute CMV infection (another herpesvirus), toxoplasmosis (a parasitic infection from cats), and even acute HIV infection. Most of the cases we see in the office turn out to be someone who had EBV infection sometime in the past. We end up searching for alternative causes of their symptoms other than EBV.
For a short discussion covering other types of herpesvirus infections, see an older blog post here.