The Belgian returned to action at the Tour of Oman this week, but his career was in jeopardy last month when he came close to having his arm amputated.
"I'm happy…. I've still got my arm," Boonen said. "That's a bit more important than having good form.
"That's what they told me, eight hours. If it hits the bone, the arm was gone and it was only a few millimetres from the bone. On the Friday there was nothing but then on Sunday they told me that if I hadn't done anything, Monday would have been too late."
The infection stemmed from a wound on Boonen's elbow and quickly escalated into a serious problem, requiring a week-long stay in hospital.
"Everybody has it on their skin but if it goes in your body and your wound closes and the crust forms, it starts breeding," Boonen explained.
"Your elbow is probably the worst place to have it because there is no blood circulation. Otherwise the white cells kill it. But it had time to breed and got strong enough to attack the rest of my body."
Boonen made his season debut in Monday's opening stage of the Tour of Oman, where he finished fifth in a bunch sprint at the end of the ride from Al Musannah to Muscat.