First Confirmed US Cases of Covid-19 Re-Infections Have Been Documented

According to a new report that has not yet been peer reviewed, a 42-year-old man in Virginia and a 25-year-old man from Nevada experienced reinfections from Covid-19, two months after they tested positive for the first time. Gene tests indicated that both men were infected with slightly different strains of virus than before. It suggests the possibility of re-infecting twice. Research findings were published in medRxiv.

After the second wave, about Covid-19 re-infections have been reported globally, from Belgium, Hong Kong, the Netherlands, India, and Ecuador. A third confirmed documented cases of reinfection is reported in US, in a 60-year-old in Washington.

Scientists explain that the risk of re-infection with SARS-CoV-2 after primary infection is plausible. However, it is unlikely that virus transmits after 10 days, or possibly up to 20 days in patients with weak immune system. From Korea, a large cases series found lack of transmission events from symptomatic patients repeatedly positive for SARS-CoV-2 after negative testing. Most case reports don’t differentiate between the prolonged shedding and reinfection.

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Study explained that after the SARS-CoV-2 infection, most persons develop anti-SARS-CoV-2 antibody responses which is characterized by rising IgG, IgM and IgA antibodies to viral spike, receptor binding domain (RBD) which are critical for viral entry.

By 4 weeks after symptoms onset, IgM and IgA antibodies decline substantially, while IgG levels remain persistent with mild or asymptomatic infections after severe Covid-19 illnesses. Study evidences indicate that the SARS-CoV-2-specific antibodies can be protective, which is indicated by the lack of infection in those with pre-existing neutralizing antibodies (nAbs) in a recent high attack rate outbreak aboard a fishing vessel.

Recovery from COVID-19 is associated with production of anti-SARS-CoV-2 antibodies, but it is uncertain whether its substantially confer immunity. In the study researchers described that the virus DNA shedding duration in hospitalized patients and identify patients with recurrent shedding. They sequenced viruses from two distinct episodes of symptomatic Covid-19 which is separated by 140 days in a single patient.

Between March 1st and August 12th, 2020, 11,622 patients were tested for SARSCoV-2 by rt-PCR, where 643 patients had at least one positive test (5.5% positivity) and 176 patients had at least two positive samples. “Time from first positive to last positive was determined as the shedding duration”. The median shedding duration observed was 12.1 days, with a positively skewed distribution. Shedding was 75 days in only two patients. Re-positivity was observed in 43 patients.

These research evidences provide in-depth assessment of immune system responses generated during reinfection. Furthermore, it provides the initial point that described a benchmark that was not protective against reinfection.

“Coronaviruses are known to reinfect people — the seasonal ones — and so it’s not very surprising to see reinfections occurring with this particular coronavirus,” said Akiko Iwasaki, PhD, an immune-biologist at Yale University.

Source: CDC

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