The tour operator in Japan was diagnosed with the virus after developing a sore throat and chest pains. This is the first such case where a person has contracted coronavirus twice in Japan after scientists raised concerns about the potential for reinfection.
The woman, in her 40s and a citizen of Osaka in western Japan first tested positive on January 29.
She was discharged from hospital after making a recovery on February 1.
Health Minister Katsunobu Kato said the central government would need to review patient lists and keep tabs on the condition of those previously discharged, as health experts analysed the implications of testing positive for the virus after an initial recovery.
Professor Philip Tierno, of New York University’s school of medicine, said: “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.
He said much remained unknown about the virus: “I’m not certain that this is not bi-phasic, like anthrax.”
Dr Babak Ashrafi, from UK-based online doctor Zava, told Metro.co.uk: “Experts are busy gathering information from those who have become infected to see how well their immune systems react and how long they’ll remain immune.
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Tokyo has urged big gatherings and sports events are scrapped or curtailed for two weeks to contain the virus while pledging the 2020 Olympic Games will go ahead in the city.
The more than 190 cases are separate from 704 reported from an outbreak on the Diamond Princess cruise liner that was quarantined off Tokyo earlier this month.
Though a first known case for Japan, second positive tests have been reported in China, where the disease originated late last year.
The outbreak has spread rapidly and widely, infecting about 80,000 people globally and killing nearly 2,800, the vast majority in mainland China.