Jakarta/Denpasar, Indonesia - Nearly a month after the World Health Organization (WHO) declared the coronavirus outbreak a global health emergency, Indonesia is yet to report a single case.

Some experts, however, are raising questions over the lack of reported cases in the country, given its close links to China, where the virus was first detected in late December.

Researchers at Harvard University in the United States have suggested there could be "undetected cases" in Indonesia, the world's fourth most populous country, and have recommended Jakarta strengthen its detection systems.

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In a study published on February 11, the researchers said Indonesia is expected to have approximately five cases. They arrived at the figure using mathematical modelling based on air travel volume estimates between the country and the central Chinese city of Wuhan, the epicentre of the new coronavirus that has now killed more than 1,800 people and infected more than 72,000 people worldwide.

According to figures cited by the Jakarta Post, approximately 98,700 passengers from Wuhan visited Indonesia between December 2018 and November 2019, making it the sixth-most popular international destination for tourists from the Chinese city. The top destinations for Wuhan travellers - Thailand, Malaysia, Singapore, Japan and Hong Kong - have all reported coronavirus cases.

The issue has garnered nationwide debate in Indonesia, with the country's health minister Terawan Agus Putranto calling the Harvard study "insulting" and arguing Jakarta has not yet recorded a single case "all because of prayers".

Achmad Yurianto, a senior official at Indonesia's health ministry, also dismissed the study's findings, noting they were based on mathematical models.

"But then Harvard also forgot that Indonesia's air is not like the air in China that is subtropical," Yurianto told Al Jazeera, repeating an as-of-yet unverified claim that the new coronavirus is similar to the pathogen that causes the seasonal flu, a disease that is more prevalent during colder weather.

He added that the Indonesian government was prepared for a potential viral outbreak, saying it has already set in place an "early warning system" for epidemics following the 2002-2003 outbreak of the severe acute respiratory syndrome (SARS), which also originated in China.

Authorities have also designated 100 hospitals across the country to respond to potential cases and tightened monitoring of passengers at the airports. Officials at Indonesian airports are using thermal scanners and thermometer guns at arrival gates, he said, and passengers are told to go to the hospital "if they feel unwell within 14 days".

Marc Lipsitch, one of the five authors of the Harvard study, in a video posted on YouTube, said the goal of their research was to criticise the quality of a country's surveillance systems. "The five is based on what other countries are detecting. It could be that there are zero [cases in Indonesia], but that's very unlikely, [and] it could be there are more".

In a subsequent interview with Al Jazeera, the professor of epidemiology at the Harvard TH Chan School of Public Health said in the event that the virus had been imported to Indonesia, there was "good chance" of secondary cases in the country.

He added: "I have emphasised that many countries, not only Indonesia, probably face the same issue: detection at the border is not 100-percent effective, even with excellent levels of testing."

The researchers' predictions were lent weight when the Huainan Centre for Disease Control and Prevention in China said a Chinese tourist who had travelled to the Indonesian tourist hub of Bali in January was confirmed to have been infected with the coronavirus on February 5, eight days after he left Indonesia.

The patient took a flight by Indonesian airline Lion Air from Wuhan to Denpasar in Bali on January 22, and flew back to Shanghai via a Garuda Indonesia flight on January 28, according to the post on Chinese microblogging site Weibo.

Dirga Sakti Rambe, doctor of internal medicine at Omni Hospitals Pulomas in the Indonesian capital, Jakarta, said it was "very possible" for the coronavirus to have reached Indonesia, but remain undetected, especially if infected people show mild symptoms.

The WHO on Monday said more than 80 percent of patients with the new coronavirus show mild symptoms, while those who become critically ill are older patients or people with other medical conditions.

Commenting on the Bali case, Rambe noted the virus's incubation period could last from two to 14 days. "So it is still possible for the patient to have been infected before coming to Bali, while in Bali, or after returning from Bali," he said.

But Yurianto, the Indonesian health official, said authorities are yet to detect any cases in Bali. Indonesia's government was not able to track the locations the man had visited during his time in Bali, but is conducting active surveillance on the island, he said.

"We examined the data until January 28," he said. "It turned out that our surveillance related to the influenza-like illness in all of Bali had no significant change. That means he was not a source of transmission because the numbers did not change much."

However, the government has suspended some 260 flights from Bali to a number of cities in mainland China since February 5 to limit the spread of the virus.

The WHO in Geneva said the cancellation of flights from Wuhan has "significantly delayed the probability" of the disease spread.

"We need to acknowledge that the relatively low number of cases of the virus detected outside of China is as a result of the intensive efforts the Chinese government is taking to contain the emergency and protect other countries," the global health agency said, referring to a lockdown imposed on Wuhan and surrounding cities in the Hubei province.

Meanwhile, Hariyadi Sukamdani, chairman of the Indonesian Association of Hotels & Restaurants, told CNBC Indonesia that Bali might lose $200m in tourism revenue and 180,000 tourist arrivals in two months due to the coronavirus outbreak, as January and February are the peak season for Chinese tourists visiting the island.

I Gusti Ngurah Adi Mahendra, owner of Bali OneTwo Trip tour agency, said he was worried about the latest situation.

"Aside from the number of visiting tourists plummeting, it has affected the tourism and the economy, and also our health," he told Al Jazeera. "Because we are working in tourism where we have direct contact with tourists. I still have to be alert."