"Last week, in the middle of my Key West vacation, I began not to feel well. Nothing serious, just under the weather," the Good Morning America
co-host wrote on her Facebook page
. Roberts, 52, explained that she then contacted her doctors, who suggested that she fly back to New York and enter the hospital a few days for observation. "Seems my young immune system needed a little boost to fight off 'opportunistic infections,'" she explained.