geoffrey modest medical blogs

A Korean CDC press release on May 19 analyzed 447 Covid-19 cases that were re-positive (i.e. the PCR went from positive, to negative, then back to positive: a finding in several other but much smaller studies), see  https://www.cdc.go.kr/board/board.es?mid=a30402000000&bid=0030&act=view&list_no=367267&nPage=1   Details: -- the Korean CDC, having found many cases of people going from positive to negative PCR and being discharged from isolation, but then turning PCR positive, decided to assess the communicability of SARS-CoV-2 in this group; they had been managing these cases as if they were newly confirmed Covid-19 cases -- in 3 areas of Korea reporting, between 26% and 49% of the cases tested positive again after negative tests (ie, re-positivity is quite common) -- 447 re-positive cases were identified; epidemiologic and contact investigation were completed for 285 of them      -- for these 285 re-positive cases, 790    contacts were identified (351 family members, 439

A recent analysis suggested that using irradiation to sterilize N95 masks led to dramatically decreased effectiveness, despite their still passing the “Fit test” (see  covid N95 irradiation jama2020  in dropbox, or doi:10.1001/jamanetworkopen.2020.9961)   Details: -- viral inactivation of SARS-CoV-2 has been reported at doses   of 10 kGy  of radiation -- 3 different  N95 masks were irradiated using a cobalt-60 irradiator, with 3 masks of each type receiving 0 kGy (control), 10 kGy and 50 kGy of gamma irradiation -- all 3 masks were subjected to the standard OSHA Fit test 50 -- another set of masks were tested for their particulate single-pass filtration efficiency, with particle sized 0.3, 0.5, and 1 µm (the actual diameter of the SARS-CoV-2 virus is 0.1  µm)   Results: -- all 9 of the tested control and irradiated N95 masks, when donned properly, passed the qualitative Fit test -- there was marked degradation of filtration efficiency for all treated masks. The following graph compares