A 33-year old man was found to have a second SARS-CoV-2 infection some four-and-a-half months after he was diagnosed with his first, from which he recovered. The man, who showed no symptoms, was diagnosed when he returned to Hong Kong after a trip to Spain.
I am a virologist with expertise in coronaviruses and enteroviruses, and I’ve been curious about reinfections since the beginning of the pandemic. Because people infected with SARS-CoV-2 can often test positive for the virus for weeks to months, likely due to the sensitivity of the test and leftover RNA fragments, the only way to really answer the question of reinfection is by sequencing the viral genome at the time of each infection and looking for differences in the genetic code.
There is no published peer-review report on this man – only a press release from the University of Hong Kong – although reports say the work will be published in the journal Clinical Infectious Diseases. Here I address some questions raised by the current news reports.
How different is the second strain that infected the Hong Kong man?
“Strain” has a particular definition when referring to viruses. Often a different “strain” is a virus that behaves differently in some way. The coronavirus that infected this man in Europe is likely not a new strain.
A STAT News article reports that the genetic make up of the sequenced virus from the patient’s second infection had 24 nucleotides – building blocks of the virus’s RNA genome – that differed from the SARS-CoV-2 isolate that infected him the first time.
