Unfortunately, I can’t work up a sense of grievance that nobody credited Yves for the role her scoop played in Meng’s auto-defenestration yesterday. For the record, here are the publications that did, as of this writing:
Calpers investment chief resigns after 18 months at $400bn fund FT. “A person close to Calpers said Mr Meng had been after the Naked Capitalism website published allegations that the executive had failed to fully comply with the California Fair Political Practices Commission in relation to financial disclosure documents.”
Now to derive an estimate of infectious dose, consider the March 2020 Skagit Valley Chorale superspreading incident inthe United States, where an infected person transmitted the disease to 52 other individuals in a 61-member choir group. Exposure time there was reported to be 2.5 hours; consequently, for an average RNA load (assuming that the carrier had mild-to-moderate symptoms), the number of virions depositing at a closely-positioned susceptible individual’s nasopharynx over that duration approximates to (11/5) x 2.5 x 60 ≈ 330. So, 300 can be considered a conservative upper estimate for the COVID-19 infective dose, the order agreeing with preliminary estimates from replication rates of the virus. That the number of virions needed to establish the infection is, at most, O(102) is indeed remarkable! The scale clearly manifests how communicable this disease is, especially if discerned in the perspective of infectious doses for other airborne transmissions, e.g. the infective dose for influenza A virus, when administered through aerosols to human subjects lacking serum neutralizing antibodies, ranges between 1950 – 3000 virions. The discovery of infectious dose, together with this study’s detection of droplet sizes that target the infection-prone nasopharynx, could provide a useful resource in mitigating the COVID-19 pandemic and in the mechanistic design of topical anti-viral therapeutics and targeted intra-nasal vaccines that can induce prophylaxis through mucosal and systemic immune responses.
The nose knows….
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Povidone iodine (letter) Nature (J-LS). From May, still germane: “PVP-I has been shown to be a safe therapy when used as a mouthwash or taken nasally.” Nasal spray would certainly be more convenient after, say, taking public transportation. And from the same authors–
The Use of Povidone Iodine Nasal Spray and Mouthwash During the Current COVID-19 Pandemic May Reduce Cross Infection and Protect Healthcare Workers SSRN. From March. “In early SARS-CoV-2 infection, viral titres of greater than 107/mL in saliva and nasal mucous can be found; minimisation of these titres should help to reduce cross infection. Povidone-iodine (PVP-I) disinfectant has better anti-viral activity than other antiseptics and has already been proven to be an extremely effective virucide in vitro against severe acute respiratory syndrome and Middle East respiratory syndrome coronaviruses (SARS-CoV and MERS-CoV). Its in vivo virucidal activity is unknown, but it retains its antimicrobial activity against bacteria in vivo intraorally and one application can reduce oral microbial flora for greater than 3 hours.”
A family member teaches at this high school in Georgia (North Paulding High) that’s made the news. Teachers and students were told they could be suspended if they posted photos of the school in a bad light. The student who took this photo for the yearbook has been suspended. pic.twitter.com/plds4vZPNN