A preliminary report based on the first 184 cases by Japan's National Institute of Infectious Diseases (NIID) estimated that most of the transmission on the ship had occurred before the quarantine.[1] The cruise line, Princess Cruises, had first assumed there was only minimal risk and had initiated only the lowest-level protocols for outbreaks before the quarantine.[46] By 27 February, at least 150 of the crew members had tested positive for the virus.[47][48] Dr. Norio Ohmagari, top government adviser and director of Japan's Disease Control and Prevention Center admitted that the quarantine process might not have been perfect.[47] A crew member reported that many of the crew had been expected to still work and interact with passengers even under the quarantine.[49][50] Princess Cruises stated that Japan's ministry of health was the lead authority defining and executing quarantine protocols, yet Japan's ministry of foreign affairs stated that a criteria of behavior was presented but the ultimate responsibility for safe environment rested with the ship operator.[49] Food service workers were found to have likely been the main early route of spread.[51] 46.5% of the infected passengers and crew members had no symptoms at the time of testing.[52][9][10] The ship outbreak had a basic reproduction number of 14.8;[53] much higher than the usual 2–4.[54] Calculations indicate that an early evacuation could have reduced the case number to just 76 cases, and that the applied quarantine reduced the case number by about 2300 cases.[53]