The patient walked into the Washoe County community testing station in the US state of Nevada on April 18 with a sore throat, dry cough and a headache, but no reason to worry.
He was only 25, had no prior medical conditions, and although the PCR nasal-swab test for Covid-19 he took came back positive, he was soon feeling well again.
Thirty five days later, he was rushed to the emergency room, short of breath and with a raging fever, and placed on oxygen support.
He had become the first confirmed US case of Covid-19 reinfection.
Up to now, there have been only a handful of similar cases worldwide, and experts say it is too early to draw sweeping conclusions from such a small head count.
But the prospect of getting reinfected with Covid-19 — and getting even sicker the second time around — could have a significant impact on