As is often the case, your remarks and suggestions inspired me to have another look at animals and on Sweden (no connection between both.
PAPERS on ANIMAL MODELS
Syrian hamsters as a model for SARS-CoV-2 infection (Sin Fun Sia Nature July 2020): a short and moderate SARS-CoV-2 infection (with transient long consolidation and objective weight loss) during 1-2 weeks, but interesting characteristics, instructive for human situation:
- Transmissible efficiently on day 2 pi via direct contact (same cage) or neighboring cages: evidence for aerosol.
- Much less transmissible via “fomites” (infected cages)
- Clear infection of olfactory tract en GI infection.
- Viral RNA can still be detected after recovery (total 14 days), while infectious period is much shorter (max 6 days).
- Development of neut Ab.
Type1/3 IFN as important mediator of protection and pathogenesis in hamsters (Boudewijn Nature Comm 2020):
- Confirmation that mice are a poor model for SARS-CoV-2, but yet more infection and pathology in mice KO for type 1 or type 3 IFN-receptor
- In Syrian hamsters a genetic defect of STAT-2 (STAT-2 KO) resulted in much higher infectious viral titers in the lungs and dissemination of virus systemically. However, the STAT-2 KO showed also much less lung pathology and less inflammation ! (STAT-2 is needed for signaling of type 1 and type 3 IFN)
A single-dose live-attenuated YF17D-vectored 1 SARS-CoV2 vaccine candidate (Dallmeier bioRxiv July 2020):
- Insertion of the prefusion (S0 spike) between prM/E and Non-structural proteins of YF17D results in attenuation in culture and mice. (S1/2 and S1 have a similar attentuatiin effects, but were not pursued for vaccination)
- A single injection of the SO-YF17D inducec neut Ab and Th1 responses and also protected against high dose challenge, with evidence of sterile immunity.
Interesting overview of various animal models (Muñoz-Fontela Nature 22 Oct): Hamsters and NH primatesemerge as best models, although minks, ferrets, cats also possible as well as ACE-2 transgenic mice. Interestingly, aged primates are more susceptible to severe disease and high viral loads.
CONTRASTING VIEWS on “the Swedish exception”: colleagues around me keep on quarreling about Sweden and Scandinavia and sending opinion papers. Honestly, I feel a bit tired about the issue, since we are struggling in this part of the world, but I’ll send you three of those papers for consideration.
- Grectchen Vogel wrote a large critical appraisal in Science magazine a month ago. The impression you get is that many Swedish scientist heavily disagree, but feel threatened, while the “official Sweden” still sticks to its “mantras”, while shifting in practice towards a more average European approach.
- Matt Steinglass in “The economist” (17 Nov) states that the other Nordic countries will certainly not adopt the relaxed Swedish example, while the Swedes are generally happy with their exceptional status as well.
- John Miltimore in Foundation for Economic Education argues that lockdowns have been even less strict in Norway and Finland than in Sweden. Yet these countries have better outcomes, both in terms of public health, citizens well-being and economy; than the rest of Europe.
In my opinion, all those views are based on very partial and biased looks on a complex reality that I would like to understand better…. But my very preliminary impression is that there are two crucial factors:
- Taking appropriate measures in time, with clear, consistent communication by authorities that are competent and well-organized.
- Trust of the population in the authorities and willingness to take responsibility for each other and for the common good.
As a Belgian citizen, I can only regret that most of those conditions were lacking for a long time in my country (and in many other West-European countries)…. Northern Europe and East-Asia have done a much better job, resulting in much less humanitarian and economic damage.
Best wishes and nice WE,
1 Nov Episode 79 Increasing diagnostic capacity by pooling and increasing sensitivity by ddPCR
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