South Korea reported on Friday that 91 recovered coronavirus patients have tested positive for the disease again, raising questions over health experts' understanding of the pandemic.
The prospect of people being re-infected with the virus is of international concern, as many countries are hoping that infected populations will develop sufficient immunity to prevent a resurgence of the pandemic.
The reports have also prompted fears the virus may remain active in patients for much longer than was previously thought.
Recovered coronavirus patients test positive again in blow to immunity hopes
scary.