Sometimes, the liver and spleen are affected and enlarged. Duration is from one to several weeks. A small proportion of affected people can take months to return to their normal energy level. There is no evidence that this is due to abnormal persistence of the infection in a chronic form. The disease is more severe in older adults, but very rarely is the disease fatal.
Symptoms appear from four to six weeks after exposure.
The virus is shed in the throat during the illness and for up to a year after infection. After the initial infection, the virus tends to become dormant for a prolonged period and can later reactivate and be shed from the throat again. No treatment other than rest is needed in the vast majority of affected people. Due to the risk of rupture of the spleen, contact sports should be avoided until clearance has been given by a physician. Avoid activities involving the transfer of saliva with someone who is currently or recently infected.