Second Time Around?

A report that a Japanese woman tested positive for Covid-19; was later recorded as 'clear' and, still later, tested positive again, has caused people to ask whether one can catch the infection twice (https://www.theguardian.com/world/2020/mar/16/the-big-question-over-coronavirus-can-a-person-get-it-twice). The answer appears to be that this is unlikely, especially in the short term (with, of course, the proviso that the virus doesn't mutate rapidly, 'returning' from some part of the world like influenza). Second infections by viral agents rarely do occur (e.g. Shingles) but these are generally after long periods of time. Immunity developed after exposures to viruses, are generally sufficient protection and long-term persistence of the virus in living tissues has only been demonstrated thus far in bats. One must also note that there are occasional failures in any testing regime and the Japanese woman may have been one such. There is, of course, an awful lot to still learn about this coronavirus.