"Glandular fever" is an illness caused by a virus. It affects the glands in our body, especially the ones in the neck and throat. This illness can make you feel very tired, have a sore throat, and cause swollen glands. Full definition
Since coming down with glandular fever over winter she's lost all her stamina. (housegoeshome.com)
(They met in a dining hall at the 1992 Barcelona Games, at which Smith performed without distinction and de Bruin not at all; he pulled out a month beforehand, he said, because of lingering weakness from glandular fever.) (si.com)
Other infections such as Epstein - Barr virus, the cause of glandular fever, may also hide and persist for many years, but become active when the immune system is compromised. (sciencedaily.com)