Infectious mononucleosis is a disease of the lymphocytes (white cells) that is caused by infection with the Epstein-Barr virus.  Typical symptoms include: sore throat, fever, swollen glands, and exhaustion.  Often the liver and the spleen are infected and swollen and skin rashes are also seen.

The seriousness varies widely. Some persons get mono and don’t know it, while others must have complete bed rest for weeks and may take a year to achieve full recovery.  It is rare to get the infection twice.

The diagnosis is made in a person with appropriate symptoms who has a positive mono test.  Often , atypical lymphocytes (white blood cells that have responded to the virus) are seen on a blood slide examined under a microscope.

After a mono infection the blood test usually remains positive for 3-6 months but can stay positive for up to a year.