3 April: Update on contact tracing, association with HIV and overview on Coronaviruses

Sat, 04/04/2020 - 10:35

Dear colleagues,

I have been reading various interesting papers, but these are the ones I would like to share.

  1. The Science paper on digital contact tracing is mainly interesting because it first tries to calculate a number of epidemiological parameters of SARS-CoV-2.  Based on published data (which, for some aspects, are sometimes scarce, the authors estimate that the reproductive number (R0) of this virus in an uncontrolled epidemic is about 2 (Table 2 on p. 13).  In this value, four transmission sources are represented as follows:
  • Pre-symptomatic patients 0.9
  • Symptomatic patients 0.8
  • Environmental (contaminated surfaces, etc): 0.2
  • Asymptomatic infected subjects: 0.1

Reading this paper and some of the references they quote and watching the epidemics in Europe continue to increase, despite weeks of “lockdown”, I’m not so sure about the rather low contribution of environmental contamination and asymptomatic subjects they propose. This is clearly something that needs to be investigated more thoroughly. More reliable estimates may become available, once we have access to population-based serological studies, coupled with clinical data: what proportion of the “seropositive” people (having antibodies) will have shown symptoms or no symptoms?

The paper provides good arguments for an app-based approach to perform contact tracing and isolation, in the stage where the European epidemic is: a classical approach with HCW who question the whereabouts of each positive subject and look physically is clearly beyond feasibility and a vaccine or treatment will not be available soon enough.  Ethical considerations are also well explained.  But will citizens in a democratic non-hierarchical society be willing to cooperate in such a “Big Brother” game?

  1. I attended the WHO-IAS Webinar this morning.  You can find the webinar and the slides at https://www.iasociety.org/HIV-Programmes/Cross-cutting-issues/COVID-19-and-HIV-Webinars  To be honest, I was not impressed by the first two speakers, but public health colleagues may have a different appreciation. The 3rd speaker was Dr. Olivier Nawej Tshikung, who studied at UCL (Louvain, not Leuven) and is now taking care of HIV patients in Geneva. Especially slides 8-13 are interesting for HIV clinicians.  His conclusion was “COVID-19  did not seem to disproportionally affect PLWH”, consistent with case reports in China. Also interesting for clinicians are the following sites on HIV and COVID drug interactions: https://www.hiv-druginteractions.org/ and https://www.covid19-druginteractions.org/
  1. The next paper briefly reminds the history of Coronaviruses. It is a kind of short introduction, pleasant to read. Two points of interest:
  • The polymerase of Coronaviruses has a proofreading capacity and the natural capacity to exert recombination. That could interesting consequences. The “proof-reading” could result in a low mutation frequency, hence not too much “antigenic drift”, but the recombination could lead to new CoV by an “antigenic shift” mechanism.  Obviously, the former characteristic is reassuring, because it might favor build-up of herd immunity and facilitate vaccine development, but the latter could be at the basis of sudden new variants that are partly resistant to herd immunity and produce new epidemics even in vaccinated subjects.
  • Remdesivir is in fact a rather broad spectrum anti-CoV drug with low µM activity. So it will be interesting to look out for ongoing clinical trials and for new variant molecules, based on Remdesivir. See the last paper.   

Quote of the dayThe latest outbreak of SARS-CoV-2 has paralyzed the world, and mobilized the scientific community.” (Susan Weiss in 40 years  with Coronaviruses).  Sic est.