A Japanese national has reportedly tested positive for the COVID-19 coronavirus after visiting Indonesia, raising concerns about the country’s ability to detect carriers of the deadly virus.

Because of this incident, Indonesian authorities are being urged to take swift actions to prevent its spread.

Bayu Krisnamurthi, who headed the National Committee for Avian Flu Control and Pandemic Preparedness between 2006 and 2010, said the Japanese man could have transmitted the virus to others in Indonesia through droplets expelled by coughs and sneezes.

“The health authorities should quickly clarify this case. It should be assumed that the virus could have been contracted by someone else before the symptoms appeared,” Bayu told The Jakarta Post on Sunday.

Previously, Japanese public broadcaster NHK reported that the Japanese man was in his 60s, lived in Tokyo and worked at a senior care facility.

The man visited a healthcare facility in Japan on Feb. 12 after developing “cold-like symptoms” but was sent home after he was not diagnosed with pneumonia. He then worked on Feb. 13, spent Feb. 14 at home and reportedly traveled to Indonesia on a family vacation on Feb. 15.

The NHK report did not specify the man’s itinerary while in Indonesia.

The man returned to Japan on Feb. 19 and was soon hospitalized for having severe difficulty in breathing. He was said to be in “serious condition”.

Separately, the Tokyo Novel Coronavirus Infectious Disease Control Center of the Tokyo Metropolitan government’s website confirmed that a Tokyo resident in his 60s had tested positive for the disease and that his symptoms appeared on Feb. 12.

The release does not mention any travel history to Indonesia, only that the man had not been to China within the previous 14 days. The patient’s condition was listed as serious.

The man was the 29th case of COVID-19 recorded in Tokyo.

Meanwhile, the Indonesian Health Ministry's disease control and environment health directorate general secretary, Achmad Yurianto, said the ministry had contacted the Indonesian Embassy (KBRI) in Tokyo to seek confirmation about the Japanese man, but his identity remained unknown.

“We neither know his name nor which part of Indonesia [he visited]. So what can we investigate?” Yurianto told the Post on Sunday.

Foreign Ministry acting spokesperson Teuku "Faiz" Faizasyah said that there had been no official communication with the Japanese authorities about the man.

The Post tried to contact the Indonesian Embassy in Tokyo by phone on Sunday, but the line only responded with an answering machine message saying to contact the embassy during business hours.

“That’s the problem: Up until now there has been no information yet from Japan,” Yurianto said.

Airports across the country are using thermal scanners to detect persons who have contracted the coronavirus and are requiring international arrival passengers to provide health documents in the form of general declarations. Airlines must also provide passenger manifests to officials in the health office.

However, people with no health concerns on arrival might not show detectable signs of previous exposure to the coronavirus.

“We could not possibly check them all, including their phlegm,” Yurianto said.

Moreover, Bayu Krisnamurthi said the authorities should have already known the proper procedures for a virus outbreak, as there had been previous cases including the avian flu, the Middle East Respiratory Syndrome (MERS) and the Severe Acute Respiratory Syndrome (SARS), among others.

He said the authorities should at least update the public daily about the coronavirus so people can get accurate and useful information since viruses mutate.

“Citizens should also be persuaded to take preventive measures: wash hands, wear masks when sick with influenza, eat well-balanced nutritious food and, if needed, take some vitamins to increase the body’s immunity,” he said.

Meanwhile, Amin Soebandrio, the director of the Eijkman Institute for Molecular Biology, said that if the Japanese man showed no symptoms during his stay in Indonesia he could remain undetected despite already carrying the virus during the incubation period.

The coronavirus' incubation period is up to 14 days.

“This is not just in Indonesia. [The man would be undetected] in any country if no symptoms show before he returned to Japan,” Amin told the Post.

Amin said that persons infected with the virus during the incubation period could theoretically spread the virus, although they would not necessarily do so if they did not show any symptoms.

“If the person already has the symptoms then he can [spread the virus],” Amin said.

Amin said that the Indonesian government had followed proper procedures as according to the World Health Organization, including requiring health cards and quarantine travelers recently coming to China.

“So the problem is not in our ability to detect [the coronavirus] or not because we have all the measures,” Amin said.

The case is the second time a patient tested positive for COVID-19 after a visit to Indonesia.

The first, a Chinese man identified as Jin, tested positive with the virus earlier this month, eight days after returning from Bali.

According to the Johns Hopkins Center for Systems Science and Engineering (CSSE), as of Sunday evening (Jakarta time), there were 78,823 confirmed cases globally, most of whom were in China where the virus has killed 2,437 people.

Outside of mainland China, a total 1,887 cases has been confirmed in 31 countries, including Hong Kong and Macau, resulting in 20 deaths.

Japan had 135 confirmed cases with one dead, according to Johns Hopkins CSSE.

A total of 23,364 people had recovered from the disease worldwide.