The Centers for Disease Control and Prevention announced Monday that the U.S. has its second confirmed case of Middle East respiratory syndrome (MERS). CDC officials are working with the Florida Department of Health to investigate the circumstances surrounding the contraction of the virus. Like the first U.S. case, reported this month in Indiana, the victim had traveled to Saudi Arabia. On Friday, that first patient was released from the hospital to home isolation. It is unclear exactly how MERS is transmitted, but so far there have been 536 cases in 17 countries resulting in 145 deaths.