NUSA DUA, BALI (NYTIMES) - A family from Shanghai was vacationing in Singapore last month when they learnt that the new coronavirus had arrived there from China.

So they packed up and flew to the world's largest country yet to report a single case of the deadly virus: Indonesia. They landed in Bali, a major destination for Chinese tourists, on Jan 30 and have no plans to leave.

"People in Bali treat us nicely and are friendly," said Eva Qin, 36, who is travelling with her mother, husband and son. "We weren't given any health test."

Health experts have questioned why Indonesia has not yet reported a single case of novel coronavirus, even though officials were slow to halt nonstop flights from China.

Indonesia receives about 2 million Chinese tourists a year, most of them in Bali.

China's consul-general in Bali said last week that about 5,000 Chinese tourists remained in Bali, including 200 from Wuhan, where the outbreak started.

Indonesia's closest neighbours have all reported cases, including the Philippines, Singapore, Malaysia and Australia.

"So far, Indonesia is the only major country in Asia that does not have a corona case," Indonesia's security minister, Mohammad Mahfud MD, told reporters on Friday (Feb 7). "The coronavirus does not exist in Indonesia."

None of the 285 people who were evacuated from Wuhan and are now in quarantine on the Indonesian island of Natuna have shown signs of the virus, he added.

Five researchers at the Harvard T.H. Chan School of Public Health concluded in a study last week that Indonesia and Cambodia, which has reported only one case, should quickly intensify its monitoring of potential cases.

Based on a statistical analysis, the disease could have arrived in Indonesia already, the authors concluded.

"Many of the imported cases have been linked to a recent travel history from Wuhan, suggesting that air travel volume may play an important role for the risk of cases being exported outside of China," the study said.

The chairman of the Indonesian Red Cross, Jusuf Kalla, a former vice president of Indonesia, also said it was possible that the disease had already entered the country and that Indonesians might not recognize the symptoms as being coronavirus.

"Singapore has a tight system, but even there the virus got in," he said. "It's possible that there are infected people but here in Indonesia people think that it is only a regular fever or they think it is dengue fever."

Mr Kalla expressed concern about how prepared Indonesia was to handle the virus if it were to strike in remote parts of the archipelago nation where underfunded community health centres are the main health care provider.

Indonesia is the world's fourth most populous country, with nearly 270 million people scattered across 6,000 inhabited islands.

"Indonesia has many islands," he said. "We have many port cities. They all have different capabilities. I think good hospitals in Jakarta can detect it. But what about the community health centre in Flores? Or in Sulawesi? Surely the capability is limited."

Indonesia's health care system is considered underfunded by international standards, with insufficient facilities and too few doctors, nurses and midwives, according to a 2018 report by the World Health Organisation (WHO).

But the WHO country representative, Dr Navaratnasamy Paranietharan, said Indonesia is doing its best to face the new coronavirus, including screening passengers at points of entry and equipping hospitals for the arrival of suspected or diagnosed cases.

"Indonesia is doing what is possible to be prepared for and defend against the novel coronavirus," he said.

Health officials say they have tested nearly 50 suspected cases, which were all negative.

Thirty Chinese workers from a cement company in North Sulawesi were placed in 14-day quarantine last week after returning from a holiday visit to China, an immigration official said. None of them have come down with the virus, he said.

If patients with symptoms were arriving, they would have been detected, insisted Achmad Yurianto, secretary of prevention and control at the health ministry.

"We are not prepared to face a major outbreak, but we are prepared to prevent an outbreak," he said. "We are not waiting for it to happen. We in fact have tightened prevention."

Indonesia is experienced at monitoring travellers for illness, he said, because the country has long been on the lookout for another dangerous coronavirus, Middle East Respiratory Syndrome (Mers).

About 1.4 million Indonesians go each year on pilgrimages to Saudi Arabia, where they can be exposed to MERS, he said, and they are screened on their return.

"We have experienced this many times," he said. "Maybe other countries are not as diligent as Indonesia in dealing with this situation."

Indonesia has three laboratories capable of testing for the Wuhan virus, two in Jakarta, the capital, and one in Surabaya, Indonesia's second-largest city, in East Java. The labs can test 1,200 samples a day, he said.

Across the country, 100 hospitals have been designated as centres to handle suspected cases of the novel coronavirus.

Before airline travel between Indonesia and China was suspended Feb 5, there were 134 flights a week from China to Bali, bringing about 5,000 passengers a day.

The loss of new Chinese tourists could be devastating for the economy of Bali, which is highly dependent on foreign visitors. Still, some of the tourists already in Bali are doing what they can to stay.

China's consul-general in Bali, Gou Haodong, said many of the remaining Chinese tourists wanted to extend their visas rather than return home to possible quarantine or exposure to the virus.

More than 30 applied on Friday for tourist visas extensions, said immigration officials, who put the number of remaining Chinese tourists at 1,500, not 5,000.