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COVID-19 re-infection by a phylogenetically distinct SARS-coronavirus-2 strain confirmed by whole genome sequencing

Our take —

A 33-year old, healthy male in Hong Kong has been infected twice with SARS-CoV-2, ~142 days apart – the first such confirmed reinfection reported. He experienced mild symptoms during his first infection, and no symptoms during this second. Full genome sequence analysis was used to confirm that the viruses causing the two infections were distinct. It is possible that the first infection induced an immune response that prevented disease during the second infection, but no specimens are available to investigate this hypothesis. Despite a growing number of confirmed reinfections, the risk of reinfection with SARS-CoV-2 and the risk of disease during subsequent infections remain unknown.

Study design

Case Series

Study population and setting

This is a case report from a 33-year old male resident of Hong Kong.

Summary of Main Findings

The patient was previously healthy and became ill on March 23, 2020 and presented for care with productive cough, sore throat, fever and headache on March 26 where he had a sample collected that had evidence of SARS-CoV-2 RNA by RT-PCR. His symptoms resolved by March 29, though he was hospitalized – per protocol in Hong Kong – until April 14 when he had two negative RT-PCR tests 24 hours apart. One serum sample was collected from the patient ~16 days post symptom onset and no IgG antibodies were detectable. Following a visit to Spain, traveling via the United Kingdom, the patient was screened upon arrival at the Hong Kong airport on August 15, 2020 and had evidence of SARS-CoV-2 infection by RT-PCR. He was asymptomatic and was hospitalized again, per Hong Kong protocol. The cycle threshold (Ct) values of his repeat RT-PCR tests over the course of the second hospitalization increased, suggesting a decreasing viral load over the course of the second infection. A serum sample collected on the first day of the second hospitalization had no detectable IgG antibodies, but a sample collected 5 days post hospitalization did have IgG. Full genome sequencing confirmed that the two infections were caused by two distinct viruses, the second sequence matched the strain circulating in Europe at the time of his visit.

Study Strengths

The authors used full genome sequence analysis to show that the two infections were related to two distinct viral lineages in order to confirm that patient had two infections.


The patient had not developed a detectable IgG response when tested during the first infection, but the sample was collected too early to rule out development of any IgG response during the first infection. It remains unknown whether the first infection conferred any protective antibodies.

Value added

This was the first confirmed reinfection with SARS-CoV-2. Reinfection should be expected, at least in some cases, based on understanding of waning immunity to SARS-CoV-2 over time and reinfection in other coronaviruses. The risk of reinfection remains unclear, despite a growing number of confirmed reinfection reports. In this example, the second infection was asymptomatic, which could be due to some level of immune response following the first infection that protected the patient from disease during the second.

This review was posted on: 2 September 2020