Cavendish’s Dimension Data team confirmed the 33-year-old had been “unknowingly training and racing” with the virus, which causes glandular fever, for a number of months.
“This season, I’ve not felt physically myself and despite showing good numbers on the bike, I have felt that there’s been something not right,” said Cavendish, who was previously diagnosed with the virus in 2017.
“Given this and on the back of these medical results, I’m glad to now finally have some clarity as to why I haven’t been able to perform at my optimum level during this time.
“Having received expert medical advice as a result of the findings, I’ve been advised to take a period of total rest in order to fully recover.
“I’m now looking forward to taking the time necessary in order to get back to 100% fitness, before then returning to racing again at peak physical condition.
“I’d like to thank everyone for the incredible support I’ve received and I look forward to seeing you all out on the road again soon.”