Dr. Stephen Bend discusses helping fellow passengers. After the doctor on the cruise ship MV Hondius contracted the hantavirus, an American doctor onboard jumped into action to help passengers navigate the outbreak. Dr. Stephen Kornfeld, an oncologist from Bend, Oregon, told ABC News that he quickly realized he was leading the response to a full-blown medical crisis on board the cruise ship. Dr. Steve Kornfeld is shown in this undated file photo. Dr. Kornfeld spoke with ABC News while aboard the M/V Hondius. Courtesy Dr. Steve Kornfeld The ship's unidentified doctor was among the six people onboard who tested positive for the virus. One passenger, who had a probable case, died onboard. "It just kind of escalated to within 24 hours after I stepped in," Kornfeld said.…