The Japanese government confirmed on Monday 99 more people on board the quarantined Diamond Princess cruise liner were infected with novel coronavirus pneumonia, bringing the total to 454.

Of the 99 people — 85 passengers and 14 crew members — who tested positive on Monday, 19 were seriously ill, according to Japan’s Ministry of Health, Labor and Welfare.

The ministry said 43 of the infected people were Japanese, and the nationalities of the others were still to be confirmed.

“Although measures are being taken to prevent infection on board, the infection control may not be successful, and it is necessary to quickly analyze why the number of infected people is increasing,” the ministry said.

Some 3,700 passengers and crew on board the cruise ship have been kept in quarantine since early February after the outbreak of novel coronavirus pneumonia.

Monday’s update brought the total number of cases on board the vessel to 454, the largest confirmed cluster anywhere outside China. A number of countries, including the United States, Canada and Italy, are removing their citizens from the ship.

The US organized two charter flights to evacuate more than 300 people on Monday. The US State Department later announced that 14 of the evacuees were infected with the virus.

China’s Hong Kong Special Administrative Region government will arrange two chartered flights to bring back its more than 300 residents on the vessel, an official said Monday.

John Lee Ka-chiu, secretary for security of the SAR government, said at a news briefing that the government will ask the Japanese authority to transport them to Haneda Airport in Tokyo to get on the chartered flights.

The two flights will bring the Hong Kong residents back on Thursday, Lee said, adding that there will be a 14-day quarantine period upon their arrival.

Italian Foreign Minister Luigi Di Maio said that his country will send a plane to Japan to bring home 35 Italians on board.

Foreign Ministry spokesman Geng Shuang said on Monday that China is closely following the situation in Japan.

“The virus knows no borders, but the worst of times reveals the best of people,” he said during an online news conference, calling on the international community to step up cooperation and jointly tackle the challenge.

Noting that the Japanese government and people from all walks of life in Japan have so far offered sincere support and assistance to China, Geng said China will never forget it and that he wished to express its heartfelt thanks.

The spokesman said that China stands ready to share information and experience with Japan and offer support and assistance in accordance with its needs.