SINGAPORE (Reuters) - The World Health Organization (WHO) has begun an investigation into three virus infections linked to an international business meeting in Singapore last month, heightening concerns about the spread of the disease outside China.

The Grand Hyatt hotel in Singapore February 5, 2020. REUTERS/Tim Chong

The cases linked to the meeting provide more evidence that the coronavirus is spreading through human-to-human contact outside China, which the WHO has said is deeply concerning and could signal a much larger outbreak.

“WHO is coordinating with relevant ministries of health in relation to it,” spokeswoman Olivia Lawe-Davies said in response to questions from Reuters.

“As countries are stepping up surveillance, the detection of more cases of local transmission can be expected.”

The cases, in Malaysia and South Korea, have been linked to a 100-strong meeting in Singapore of staff from an as-yet-unnamed multinational sales firm, while one Chinese delegate was from the central city of Wuhan, where the virus originated.

The sister of a Malaysian who attended has since been infected, while Singapore said virus symptoms had surfaced in four of the firm’s local staff.

Authorities have not revealed the name of the company, although Korea has said it was an international sales firm.

Malaysia offered the first revelation when it confirmed the case of a 41-year-old citizen who had attended the meeting at the plush Grand Hyatt hotel near the city-state’s Orchard Road shopping district.

South Korea then confirmed two cases involving its citizens who had also attended. The Koreans and the Malaysian shared a buffet meal during the conference, South Korean media said.

Of 109 meeting participants, 94 were from overseas and have since left Singapore, its health ministry said, adding that four local staff were referred to the National Centre for Infectious Diseases.

The hotel will carry out “thorough sanitisation and deep cleaning” of guest rooms that were potentially affected and will monitor staff and guests for symptoms, its general manager, Willi Martin, said.

Singapore has reported 28 cases of the coronavirus, some involving domestic transmissions.

Several firms in Singapore have suspended business and media events, including a big travel fair and hotel trade show, but the Singapore Airshow will go ahead next week, although on a smaller scale.

On Thursday, China reported its biggest daily jump in deaths from the virus, an increase of 73 to 563, although only two deaths have been reported outside mainland China.