“Mono” (short for mononucleosis) is a viral illness that resembles strep throat and affects children after two years of age, although symptoms are worse in older kids. It is contagious through saliva, hence its nickname, “the kissing disease.” Some children, especially young ones, get very mild cases or have no symptoms at all, while in others it is quite intense and lasts for weeks. Most adults are immunized by a bout in childhood. Mono’s incubation period can last for several weeks, and then symptoms start with a painful sore throat, swollen tonsils, and a fever that can be in the 104°F range. A generalized rash on the whole body may appear for a few days. Suspicion of mono arises when symptoms suggest a strep throat infection, but the strep test your doctor performs comes back negative. Blood tests are somewhat unreliable and only of value if the diagnosis is unclear.
There is no treatment for mono except rest as needed. Fatigue can persist for weeks, especially in teenagers. The spleen may become enlarged and even rupture if subjected to a blow. For this reason, participation in violent sports should be avoided for up to a month after the illness has been diagnosed.