As an extraordinary two-week quarantine of a cruise ship ended in Japan, many scientists said it had been a failure. 

Hundreds of passengers left the Diamond Princess cruise ship after their two-week quarantine ended. Results were still pending for some passengers who've been tested for the virus that has sickened tens of thousands of people in China.

Some passengers said they received health check forms asking if they had any symptoms such as headache, fever, cough. Passengers who tested negative and had no symptoms still had to get their body temperature checked before leaving. 

A Japanese passenger said he was still waiting for his virus results and was getting worried.

The Diamond Princess cruise ship seemed to serve as an incubator for the new virus from China instead of an isolation facility meant to prevent the worsening of an outbreak. 

Authorities on Wednesday announced 79 new cases, bringing the total on the ship to 621, by far the largest number outside mainland China. 

Experts say an investigation is needed to determine why the quarantine failed and if there's another mode of transmission aboard the ship. One ethicist says the failure was tragic but that the quarantine, which ends Wednesday, was justified. 

The Centers for Disease Control said Tuesday that it believes the rate of new infections on board the ship, especially among those without symptoms, still represents an ongoing risk. 

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"Therefore, to protect the health of the American public, all passengers and crew of the ship have been placed under travel restrictions, preventing them from returning to the United States for at least 14 days after they had left the Diamond Princess," the CDC said in a statement. 

Japan Outbreak Cruise Ship AP
A bus carrying passengers from the quarantined Diamond Princess cruise ship leaves a port in Yokohama, near Tokyo, Monday, Feb. 17, 2020.
AP

There were more than 100 Americans on board the Diamond Princess or in hospitals in Japan, health officials said. And said if anyone from the ship arrives back in the U.S. before the 14-day period ends, they'll have to undergo a 14-day mandatory quarantine, the CDC explained.