OK folks, it's time that we end the testing of asymptomatic people, stop contact tracing, and begin returning to normal. This new study of near 10 million residents in China from the journal 'Nature' shows that asymptomatic transmission is extremely rare (which is what we have always known based on past pandemics).
https://www.nature.com/articles/s41467-020-19802-w#MOESM1
The authors' findings and conclusions:
**A total of 1174 close contacts of the asymptomatic positive cases were traced, and they all tested negative for the COVID-19.
**Virus cultures were negative for all asymptomatic positive and repositive cases, indicating no "viable virus" in positive cases detected in this study.
**None of detected positive cases or their close contacts became symptomatic or newly confirmed with COVID-19 during the isolation period.
**Testing of antibody against SARS-CoV-2 virus was positive IgG (+) in 190 of the 300 asymptomatic cases, indicating that 63.3% (95% CI 57.668.8%) of asymptomatic positive cases were actually infected. The proportion of asymptomatic positive cases with both IgM () and IgG () was 36.7% (95% CI: 31.242.4%; n = 110), indicating the possibility of infection window or false positive results of the nucleic acid testing.
**Previous studies have shown that asymptomatic individuals infected with SARS-CoV-2 virus were infectious, and might subsequently become symptomatic. Compared with symptomatic patients, asymptomatic infected persons generally have low quantity of viral loads and a short duration of viral shedding, which decrease the transmission risk of SARS-CoV-25. In the present study, virus culture was carried out on samples from asymptomatic positive cases, and found no viable SARS-CoV-2 virus. All close contacts of the asymptomatic positive cases tested negative, indicating that the asymptomatic positive cases detected in this study were unlikely to be infectious.**
Regarding PCR Ct values: A cycle threshold value (Ct-value) less than 37 was defined as a positive result, and no Ct-value or a Ct-value of 40 or more was defined as a negative result. For Ct-values ranging from 37 to 40, the sample was retested. If the retest result remained less than 40 and the amplification curve had obvious peak, the sample was classified as positive; otherwise, it was reported as being negative.
Note that in the USA, a Ct threshhold of 40 is used, which is going to generate significantly more false positives.
And remember this from Dr. Anthony Fauci back in March...
https://www.nature.com/articles/s41467-020-19802-w#MOESM1
The authors' findings and conclusions:
**A total of 1174 close contacts of the asymptomatic positive cases were traced, and they all tested negative for the COVID-19.
**Virus cultures were negative for all asymptomatic positive and repositive cases, indicating no "viable virus" in positive cases detected in this study.
**None of detected positive cases or their close contacts became symptomatic or newly confirmed with COVID-19 during the isolation period.
**Testing of antibody against SARS-CoV-2 virus was positive IgG (+) in 190 of the 300 asymptomatic cases, indicating that 63.3% (95% CI 57.668.8%) of asymptomatic positive cases were actually infected. The proportion of asymptomatic positive cases with both IgM () and IgG () was 36.7% (95% CI: 31.242.4%; n = 110), indicating the possibility of infection window or false positive results of the nucleic acid testing.
**Previous studies have shown that asymptomatic individuals infected with SARS-CoV-2 virus were infectious, and might subsequently become symptomatic. Compared with symptomatic patients, asymptomatic infected persons generally have low quantity of viral loads and a short duration of viral shedding, which decrease the transmission risk of SARS-CoV-25. In the present study, virus culture was carried out on samples from asymptomatic positive cases, and found no viable SARS-CoV-2 virus. All close contacts of the asymptomatic positive cases tested negative, indicating that the asymptomatic positive cases detected in this study were unlikely to be infectious.**
Regarding PCR Ct values: A cycle threshold value (Ct-value) less than 37 was defined as a positive result, and no Ct-value or a Ct-value of 40 or more was defined as a negative result. For Ct-values ranging from 37 to 40, the sample was retested. If the retest result remained less than 40 and the amplification curve had obvious peak, the sample was classified as positive; otherwise, it was reported as being negative.
Note that in the USA, a Ct threshhold of 40 is used, which is going to generate significantly more false positives.
And remember this from Dr. Anthony Fauci back in March...