John's rep told ABC News that after the singer returned from a tour in South America earlier this month, he was hospitalized for some time and spent two nights in intensive care.
He was released from the hospital this past Saturday and, under the counsel of his doctor, is "comfortably resting at home."
"I am so fortunate to have the most incredible and loyal fans and apologize for disappointing them," John said in a statement. "I am extremely grateful to the medical team for their excellence in looking after me so well."
The statement from his rep indicated that the infection that John, 70, contracted is "rare and potentially deadly," but it was quickly identified and treated. He is expected to make a full recovery.
The cancellations encompass John's entire performance schedule for April and May in Las Vegas, as well as a May 6 performance in Bakersfield, California.
His next live show will take place in Twickenham, England, on June 3.
Ticket holders can get refunds for the canceled performances.