A woman working as a tour bus guide in Japan has tested positive for coronavirus for a second time, in what authorities have said is the first such case.

The woman, who is in her 40s and a resident of Osaka in western Japan, tested positive on Wednesday after developing a sore throat and chest pains, the prefectural government said. She first tested positive on 29 January and was discharged from hospital after recovering on 1 February, before testing negative on 6 February.

The development came as the prime minister, Shinzō Abe, said Japan’s entire school system, from elementary to high schools, would be asked to close from Monday until the spring break late in March to help contain the outbreak.

The health ministry confirmed the woman’s case was the first in Japan where a patient tested positive for a second time after being discharged from hospital.

Cases of second positive tests have been reported in China. The outbreak has spread rapidly and widely, infecting about 80,000 people globally and killing nearly 2,800, the vast majority in mainland China.

“Once you have the infection, it could remain dormant and with minimal symptoms, and then you can get an exacerbation if it finds its way into the lungs,” said Prof Philip Tierno at New York University’s school of medicine. He said much remained unknown about the virus. “I’m not certain that this is not biphasic, like anthrax,” he said, meaning the disease might appear to go away before recurring.

The number of cases in Japan rose on Thursday to more than 200, up from the official tally of 186 late on Wednesday. On the main northern island of Hokkaido, 15 new cases, including two children under the age of 10, were confirmed.

Japan’s government has called for big gatherings and sports events to be scrapped or curtailed for two weeks to contain the virus, but said the 2020 Olympics would go ahead in Tokyo. But its handling of the virus has drawn increasing criticism, including from opposition politicians.

Abe received support from the International Olympic Committee whose president, Thomas Bach, told Japanese media the IOC was fully committed to holding the Games on schedule.

Abe’s sudden announcement of school closures triggered a flurry of worries on social media among parents scrambling to arrange childcare.

“My honest feeling – all schools on break? It’s important to protect children, but what happens if they have working parents?” wrote one Twitter user.

The cases reported in Japan do not include the 705 reported from an outbreak on the Diamond Princess cruise ship that was quarantined off Yokohama earlier this month.