The illness turned out to be a "coincidental cluster of varying viruses" including a mix of the common cold and a strain of the flu, according to a press release filed by the Alabama Department of Public Health.
ABC News reports health officials first became aware of the "mystery illness" on May 16 when several patients exhibited symptoms of "cough, a fever and shortness of breath" and there was no known cause for them.
"You never want to assume that there isn't a connection, because as soon as you do that, you will be proved wrong," said Dr. Richard Besser, chief health and medical editor for ABC News. "The first cases of the next SARS or the next flu pandemic could look very much like this. You treat every one of these clusters the same: You attack it with rapid public health science."
Dr. Mary McIntyre, who is leading the investigation about the illness said the five patients who are infected but still alive seem to be getting better. One of them was released from the hospital on Tuesday.