I know that there have been other papers published, but I was specifically looking for the one referenced by Bill Bryan, an undersecretary at the Homeland Security Department, in the press briefing today (4/23/2020).

As I recollect Bryan announced that work done by the Science and Technology section of DHS, had found that exposure to strong sunlight, particularly UV, shortened the half-life of Sars-Cov-2 significantly. (He also discussed bleach, IPA, and disinfectants, but that's not my focus for this Q)

If I can find this research, it might reveal if the "sunlight exposure" was natural sunlight or artificial. The key difference being that artificial (or laboratory sunlight) tends to also contain UV-C which is highly destructive*, whereas natural sunlight has almost no UV-C (thankfully to the earth's atmosphere)

  • Laboratory sunlight can be equipped to absorb or diminish the UV-C, so I'd be looking , in the research, for actual measurements of the UV-A, UV-B and UV-C used to "attack" SARS-CoV-2 assay.
  • Reason for downvote on Q and A?
    – BobE
    Commented Apr 24, 2020 at 12:46
  • My answer is a link only answer which is frowned on. I expect the paper may eventually find its way into the public domain in its original form. Commented Apr 24, 2020 at 20:21

1 Answer 1


The paper is here https://www.scribd.com/document/456897616/DHSST#fullscreen&from_embed

It doesn't say but I presume that the Department of Homeland Security knows what sunlight is.

  • I was hoping for a paper rather than a slideshow, but alas. I was able to ascertain that they employed simulated solar light, however that doesn't address if UV-C was blocked. As a side note, on that same slide, they wondered " How much virus does it take to infect?", apparently the National Biodefense Analysis and Countermeasures team (NBACC) scientists don't know. Thanks for the lead.
    – BobE
    Commented Apr 24, 2020 at 17:33
  • @BobE This is such an interesting question "How much virus does it take to infect?", maybe breathing a very small amount of COVID-19 won't be enough to be infected, idk. Commented Apr 24, 2020 at 18:34

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