Both patients were on the same flight - Singapore Airlines SQ25 from New York via Frankfurt on Monday - as the 7th confirmed case, a 30-year-old Australian male tourist who was seated at Row 54. The flight arrived in Singapore at 6.18am that day, said a statement from the Ministry of Health on Wednesday night.

The 10th patient is a 33-year-old Singaporean female who was in New York from May 23 to 30. She was seated at row 19 on SQ25.

She went home by taxi from the airport and developed symptoms later the same morning. She remained at home for the rest of the day.

On Tuesday, she stayed at home the whole day and in the evening, took a taxi to Tan Tock Seng Hospital, where she was admitted to the Communicable Diseases Centre 2, before midnight.

The 11th case is an 18-year old American female visitor. She was seated at row 57.

She was met by her relative at the airport and they took a taxi to the relative's residence. She developed symptoms on Tuesday afternoon and took a taxi with her relative to seek medical attention at Raffles Hospital's Emergency Department in the evening. She was later sent to CDC, via a 993 ambulance. She was admitted to CDC2 in the early hours on Wednesday.

Laboratory results confirmed their infection at 3pm on Wednesday.

MOH said contact tracing has been initiated for the latest two cases.

Based on MOH's risk assessment, passengers within rows 17 to 21 and rows 57 to 59 on SQ 25 on Monday who have not been contacted by the ministry should call the MOH hotline at 1800-333 9999 to enable the authorities to check on their health condition expeditiously.

As for the 9th case, a 19-year-old Singaporean female who arrived in Singapore from New York on May 28, MOH has identified two household contacts for home quarantine orders.

'They are currently well. Contact tracing is still on-going for any other close contacts,' said MOH.

So far in Singapore, all the 11 cases are imported and have a travel history. There is currently no evidence of community spread, said MOH.