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Preliminary evidence for longer viral shedding – but similar peak viral concentration for SARS-CoV-2 infections with the variant B.1.1.7 (Kent/British-detected)

A new preprint reports preliminary evidence for longer viral shedding – but similar peak viral concentration – for SARS-CoV-2 infections (the virus that causes COVID-19) with the B.1.1.7 (Kent/British-detected) variant, vs non-B.1.1.7 isolates.

This is however again preliminary data, and note that few B.1.1.7 cases were studied in this new preprint (link here).

Methods overview

This is based on data from a rather small convenience sample of n=65 (e.g. team staff, player, vendors, 90% male) – interpret with caution.

They combined anterior nares & oropharynx tests.

Only 7 of the individuals had variant B.1.1.7 (sequencing-based confirmation)

Here they looked at
a) Duration of detectable to peak viral concentration (“proliferation phase”)
b) Duration of peak viral concentration to return non-detectable (“clearance phase”), and
c) Duration of infection (duration of proliferation + clearance phases)
d) Peak viral concentration.


They found that CT values for peak viral load were only slightly lower for B.1.1.7. Lower CT values indicate higher viral load, thus slightly higher (but quite similar) viral load was seen for B.1.1.7: ~19.0 vs ~20.2.

For the above phases:

  • The proliferation phase was ~5.3 days for B.1.1.7 vs 2.0 for non-B.1.1.7;
  • The clearance phase was ~8 days for B.1.1.7 vs 6.2 for non-B.1.1.7;
  • The infection duration (proliferation+clearance phases) was 13.3 days vs 8.2 days

(Note, some of the confidence intervals do overlap in the preprint, suggesting no significant difference betweeen B.1.1.7 and non-B.1.1.7)

  • Note that there is a recent publication linking the amount of viral shedding (i.e. which was not that altered by B.1.1.7) to the risk of transmission, as well as to the incubation period & risk of getting symptomatic COVID-19.
  • Some earlier data have found significantly higher viral load (10 and 10,000-fold) in viral load for B.1.1.7 vs. non-B.1.1.7 (although technically here they look at S-gene dropout, which could include other variants as well; because the B.1.1.7 variant and other variants have a deletion in the S gene that cause one of the primers used for PCR to fail; whereas the other ones still work – enabling labs to detect this specific deletion)
The B.1.1.7 variant is one of the variants that has been (best) characterized as likely having increased transmission vs. parental SARSCoV2 variants. The European center for disease prevention and control (ECDC) recently summarized the evidence, citing one study modeling 56% higher SARS-CoV-2 transmission by B.1.1.7 (link here).
In the new preprint, the authors call for more data & make the following point:
  • If borne out by additional data, a longer isolation period than the currently recommended 10 days after symptom onset may be needed to effectively interrupt secondary infections by this variant