Abstract
Reinfection cases have been reported in some countries with clinical symptoms ranging from mild to severe. In addition to clinical diagnosis, virus genome sequence from the first and second infection has to be confirmed to either belong to separate clades or had significant mutations for the confirmation of SARS-CoV-2 reinfection. While phylogenetic analysis with paired specimens offers the strongest evidence for reinfection, there remains concerns on the definition of SARS-CoV-2 reinfection, for reasons including accessibility to paired-samples and technical challenges in phylogenetic analysis. In light of the emergence of new SARS-CoV-2 variants that are associated with increased transmissibility and immune-escape further understanding of COVID-19 protective immunity, real-time surveillance directed at identifying COVID-19 transmission patterns, transmissibility of emerging variants and clinical implications of reinfection would be important in addressing the challenges in definition of COVID-19 reinfection and understanding the true disease burden.
Highlights
SARS-CoV-2 reinfection was confirmed by the determination of the presence of virus genome, and sequencing, in which virus genome from the first and second infection is confirmed to either belong to separate clades or had significant mutations
Nucleic acid amplification test (NAAT) that uses techniques including real-time reverse transcriptase-polymerase chain (RT-PCR) targeting viral genome is considered the gold-standard in SARS-CoV-2 laboratory diagnosis (Table 1)
In the context of common cold viruses, one study showed that reinfection of respiratory syncytial virus (RSV) in hospital-admitted infants occurred at a rate of 43% (23 out of 55) in one year [32]
Summary
Reinfection cases have been reported in Hong Kong [1], Belgium [2], the Netherlands [3], Ecuador [4], US [5,6,7,8], India [9,10], Qatar [11], France [12,13], Brazil [14], Italy [15], the UK [16,17] and Saudi Arabia [18] with clinical symptoms ranging from mild to severe. SARS-CoV-2 reinfection was confirmed by the determination of the presence of virus genome, and sequencing, in which virus genome from the first and second infection is confirmed to either belong to separate clades or had significant mutations In this context, phylogenetic analysis with paired specimens offers the strongest evidence for reinfection. While the US CDC recommends a period of at least 45 days between infection to be considered as a case of reinfection, the possibility of reinfection beyond 28-days after first infection has been reported previously [19] and in some cases, reinfection was confirmed with genome sequencing at an interval period ranging from 19 days [9] to 142 days [1] In this context, clinical and epidemiological factors should be considered during reinfection diagnosis. Sequence information of paired specimens during the first and second infection, clinical data and confirmation of interval period between the two episodes would be required
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