I'm not exactly sure what test is positive in his case. Serum testing looking at immunity and specific immunoglobulins in the blood will show a positive level on the IgG immunoglobulin in people who were infected and recovered from Mono.

I wonder about environment as relates to the illnesses that he is having. Is he in daycare or maybe a close-quarters school setting with the risk for exposure to many illnesses? The quoted number is about 2-8 fever associated illnesses per year in pre-school children.

Infection with the Epstein-Barr virus, the virus that causes Mono, is associated with cancer in some individuals - particularly a cancer known as Burkitt's lymphoma. This risk is low for developing cancer.

However, I hear your concern as a parent regarding these illnesses. It would probably be a good idea to have him checked by his pediatrician. Examining things such as his growth and weight gain will be useful. A complete blood count lab could help further evaluate your concerns.