#23341 En principio se barajan otras cosas, no que sea tema de cepas:
https://www.sciencemediacentre.org/expert-reaction-to-people-being-re-tested-positive-for-coronavirus-after-initial-recovery-e-g-case-reported-in-japan-where-a-woman-has-been-confirmed-as-a-coronavirus-case-for-2nd-time/
A - This is indeed a relapse of the illness – This was seen is SARS but in someone who was being treated with steroids. It is possible that the illness could be biphasic as suggested by Dr Tierno though this is unlikely to be common based on current information.
B - She has a prolonged excretion of virus from her initial infection and tests were either not done or were not done sufficiently well or enough to confirm clearance. It does appear that swabs for the virus are not 100% reliable. In this case it is even possible that the recent sore throat maybe unrelated. COVID-19 tends to cause upper respiratory tract symptoms rather less frequently that did SARS.
Aún hay que investigar evidentemente pero de momento los científicos no optan porque esto esté relacionado con que puedas recaer por el mismo virus si no por otras cacusas que ya se han visto anteriormente en otros casos. Y sobre todo que no es algo "habitual".