Australian infectious disease experts have warned Indonesia may potentially have numerous “undetected” cases of coronavirus, disputing one of our closest neighbour’s claims it is virus free.

Last week, Indonesia’s health ministry declared the country had recorded no cases of the potentially deadly coronavirus, adding that 238 people evacuated from the Chinese city of Wuhan had not shown any symptoms.

But a new study from Harvard University found the lack of cases identified in Indonesia and Cambodia, which has just one case, were lower than expected.

The study based its findings on the number of passengers flying from the virus epicentre in Wuhan and surrounding countries and cited the tourism and trade links between Indonesia and China.

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The study, which has not yet been peer reviewed, said Indonesia’s lack of confirmed cases could “suggest the potential for undetected cases”.

Since the beginning of the outbreak in the Chinese city of Wuhan in December 2019, coronavirus has spread to 25 countries.

Health authorities say there are now more than 43,000 confirmed cases across the world, with the death toll topping 1,000.

An estimated two million Chinese tourists holiday in Indonesia every year, many of them in Australian holiday hotspot Bali, according to Statistics Indonesia.

Australian National University's infectious diseases specialist, Associate Professor Sanjaya Senanayake, said there could be undetected cases among the vast archipelago’s population of 264 million, because sick people simply stayed home instead of going to hospital.

“It may well be the case, that they’ve detected no cases of coronavirus, it all depends on the ability of the health service to screen and detect,” he told SBS News.

“But, it’s possible there may be cases they don’t yet know about. We know a lot of people who are infected may only have a very minor infection and they may not be turning up at a hospital.

“A lot of it depends on the public health service’s messages and how they’re being communicated. In Australia for example… a person who had recently returned from Wuhan or who had come into contact with someone who had and was feeling sick, would understand the risks because of the messaging.”

Professor Senanayake said there was a risk authorities could be failing to detect coronavirus infections in countries with less developed or “already stretched” health systems, such as many African nations.

“Cases would potentially not be picked up… there are some nations that are not going to be able to identify every cases due to stretched resources,” he said.

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To date, there have been no confirmed cases of coronavirus in Africa.

Australia's Chief Medical Officer Brendan Murphy said he felt it was "very surprising" no cases had been reported in Indonesia.

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"There should be a cause for some concern. There may be undetected cases," he told ABC radio on Wednesday.

Associate Professor Adam Kamradt-Scott from the Centre for International Security Studies at the University of Sydney, said there was an increased risk for tourists in Indonesia.

“Given the high level of travel between China and Indonesia it’s possible that there could be undetected cases circulating,” Associate Professor, who is an expert in the spread and control of infectious diseases, told SBS News.

“The Indonesian health system is not as advanced as Australia’s… there are several countries in the Asia-Pacific region that are not as well equipped to deal with surveillance on this scale, of which Indonesia is one.”

But Professor Kamradt-Scott stressed that, overwhelmingly, coronavirus-linked fatalities had been over 60, male, or suffering from a pre-existing condition.

“Most Australian tourists heading to Bali however, are in their 20s or 30s through to young families,” he said.

“If it did emerge that there has been cases circulating, while Indonesia says otherwise, it would reflect very poorly on the Indonesian government.”

Indonesian health authorities have stepped up measures to counter a potential outbreak, including halting direct flights between China and the holiday island of Bali, but denied they were hiding anything.

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"We have the kits to check coronavirus and they're certified ... Nothing is concealed," Health Minister Terawan Agus Putranto told Chanel News Asia, following a cabinet meeting on Tuesday.

In an earlier statement, he said that “all (steps) have been taken to make sure that there is no outbreak”.

Indonesia’s closest neighbours, including Australia, Malaysia, Singapore, Thailand and the Philippines, have all reported cases of coronavirus but Sydney University’s contagion expert Professor Mikhail Prokopenko said it was possible Indonesia had been spared.

“If you look at the numbers, then Australia is probably more dangerous than Indonesia,” he said.

He queried the Harvard University study suggesting there are unreported cases in Indonesia, saying the report only looked at flight data and failed to take into account other factors such as geography, population density and temperature.

“It’s possible there could be unreported cases, but we have no evidence. At this stage, it’s pure speculation,” Professor Prokopenko said.

“Let’s not forget that it’s nearly 30 (degrees Celsius) at the moment in Indonesia, unlike 5 degrees in say, Japan. Sitting around the equator at these hot temperatures can explain a lot about being a lucky outlier. Singapore, with about 50 cases, on the other hand, may be an unlucky outlier.”

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The Department of Foreign Affairs and Trade urges Australians heading to Indonesia to “exercise a high degree of caution”, but has no specific warning about coronavirus for the nation.

Foreign Minister Marise Payne told a press conference on Wednesday that Australia has confirmed testing processes were in place in Indonesia and that Australia would continue to provide assistance as required.