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CMAAO Coronavirus Facts And Myth Buster - UK Strain: Longer duration of infection

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Dr KK Aggarwal    22 February 2021

With input from Dr Monica Vasudev

It was believed that B.1.1.7 variants increased infectiousness is due to higher viral load. New data suggest that it is related to delayed clearance, and longer duration of infection.

Infection duration appears to be longer for B.1.1.7, with a mean of 13.3 days (90% CI 10.1, 16.5), compared to 8.2 days for non-B.1.1.7.

A study evaluated if acute infection with B.1.1.7 is associated with higher or more sustained nasopharyngeal viral concentrations. Longitudinal PCR tests conducted in a cohort of 65 individuals with SARS-CoV-2 undergoing daily surveillance testing were evaluated.
These included seven infected with B.1.1.7.
 
For patients with B.1.1.7 variant, the mean duration of proliferation phase, clearance phase, and overall duration of infection was 5.3 days, 8.0 days, and 13.3 days, respectively. The corresponding figures for non-B.1.1.7 virus were mean proliferation phase of 2.0 days, a mean clearance phase of 6.2 days, and a mean duration of infection of 8.2 days.
 
The peak viral concentration for B.1.1.7 was 19.0 Ct vs. 20.2 Ct [19.0, 21.4] for non-B.1.1.7. This represents 8.5 log10 RNA copies/ml [7.6, 9.4] for B.1.1.7 and 8.2 log10 RNA copies/ml [7.8, 8.5] for non-B.1.1.7.
 
The variant B.1.1.7 thus appears to result in longer infections with similar peak viral concentration compared to non-B.1.1.7. 

The longer duration may result in increased transmissibility of the variant.
 
Comments
 
1.      These variants probably carry non-spike mutations that affect their sensitivities to type I (or III) interferon.
2.       Not related to higher viral load as higher load is consistent with worse outcomes. Mitigation efforts should be just as effective.

[Source: https://dash.harvard.edu/bitstream/handle/1/37366884/B117Trajectories_10Feb2021.pdf?sequence=1&isAllowed=y] 

Dr KK Aggarwal
President CMAAO, HCFI and Past National President IMA

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