Jakarta. The number of coronavirus patients from local transmission cases in Indonesia increased sharply to 19 on Monday from six a day earlier.

The 13 new patients aged between 16 dan 59 years old include two foreigners, whose nationality has not been disclosed.

"The total number of confirmed [coronavirus] cases has reached 19 as of today. They include two foreigners from a country that was the epicenter of the coronavirus outbreak. Please don't ask me about their identities," Achmad Yurianto, the government spokesman for coronavirus handling, told a press conference at the presidential office in Central Jakarta.

"Patient 7 is a 59-year-old woman who had just returned from an overseas trip. She transmitted the virus to her husband, 56, who is now called patient 8," Yurianto said.

A 16-year-old girl is the youngest patient so far whose case was linked to an earlier local transmission, he said.

The first two confirmed Covid-19 cases in Indonesia involved a mother and her daughter who hosted a dance party at Amigos Restaurant in Kemang, South Jakarta, on Valentine's Day.

Local health authorities now believed a Japanese national, who also attended the party and was later identified as Patient 24 in Malaysia, was the source of the novel coronavirus infection on that day. 

Within a week, three more people who had direct contact with the two women have tested positive for the virus. The 16-year-old girl got the virus from Patient 3, Yurianto said.

The two foreign patients were a man aged 29 and a woman aged 54, he said.

Yurianto said all but one patient are in stable conditions without the need for supplemental oxygen or intravenous feeding.

Patient 8 is an exception because he already had diarrhea and diabetes prior to contracting the SARS-CoV-2 virus, he said.