COVID19 update, June 14, 2020: avoiding the Three C’s of Transmission; most asymptomatic cases remain asymptomatic

Busy workday, so just some quick updates:

(1) (hat tip: Masgramondou): Are Technica: “Just 10-20% of cases are behind 80% of transmission” 

Benjamin Cowling, a Hong Kong-based epidemiologist and biostatistics expert, agrees. Cowling and colleagues recently studied transmission in Hong Kong, finding superspreading events drove local transmission. In a recent op-ed, he and a colleague argue that public health policies aimed at stopping the pandemic should focus on stopping superspreading.

“The epidemic’s growth can be controlled with tactics far less disruptive, socially and economically, than the extended lockdowns or other extreme forms of social distancing that much of the world has experienced over the past few months,” the researchers wrote

In an email to Ars, Cowling fleshed out this idea a bit, noting that “measures that specifically target superspreading are those that reduce or prevent large gatherings of people,” such as those to reduce the density of people in schools and workplaces.

Measures not specifically targeted to superspreading, he noted, “are those like asking everybody to stay at home as much as they can, despite many workplaces and social settings not being places that superspreading could occur.”

In the op-ed, Cowling noted that Japan—which has been relatively successful at managing the pandemic—has employed an anti-superspreading policy called [“the Three Cs Of Transmission”]: Avoid (1) Closed spaces with poor ventilation, (2) Crowded places, and (3) Close-contact settings, such as close-range conversations. The risk for superspreading is highest in situations with all three Cs.

[…]Cowling and his colleagues’ analysis has been posted online but has not yet been peer-reviewed or published in a scientific journal. But, they note, their findings from Hong Kong aren’t unique. For instance, a study published in the Lancet in April, which looked at transmission of SARS-CoV-2 in Shenzhen, China, found that just around 9 percent of cases accounted for 80 percent of transmission. And a modeling study from researchers in London likewise found that just about 10 percent of cases may account for 80 percent of transmission.

Read the whole thing.

(2) via Instapundit, this report by UPI quoting this letter to the New England Journal of Medicine from a Japanese team:

The outbreak of coronavirus disease 2019 (Covid-19) on the cruise ship Diamond Princess led to 712 persons being infected with SARS-CoV-2 among the 3711 passengers and crew members, and 410 (58%) of these infected persons were asymptomatic at the time of testing[….] A total of 96 persons infected with SARS-CoV-2 who were asymptomatic at the time of testing, along with their 32 cabinmates who tested negative on the ship, were transferred from the Diamond Princess to a hospital in central Japan between February 19 and February 26 for continued observation. Clinical signs and symptoms of Covid-19 subsequently developed in 11 of these 96 persons, a median of 4 days (interquartile range, 3 to 5; range, 3 to 7) after the first positive polymerase-chain-reaction (PCR) test, which meant that they had been presymptomatic rather than asymptomatic.

[…] The group of persons with asymptomatic SARS-CoV-2 infection consisted of 58 passengers and 32 crew members, with median age of 59.5 years (interquartile range, 36 to 68; range, 9 to 77). A total of 24 of these persons (27%) had coexisting medical conditions, including hypertension (in 20%) and diabetes (9%). The first PCR test at the hospital was performed a mean of 6 days after the initial positive PCR test on the ship. The median number of days between the first positive PCR test (either on the ship or at the hospital) and the first of the two serial negative PCR tests was 9 days (interquartile range, 6 to 11; range, 3 to 21), and the cumulative percentages of persons with resolution of infection 8 and 15 days after the first positive PCR test were 48% and 90%, respectively. The risk of delayed resolution of infection increased with increasing age.

In this cohort, the majority of asymptomatically infected persons remained asymptomatic throughout the course of the infection. The time to the resolution of infection increased with increasing age.


(3) UnHerd: so where did the virus really come from? Dogmatic answers do not behoove a scientist, as the writer rightly argues. On the other hand, extraordinary claims (e.g., a genetically engineered virus) require extraordinary proof. Either way, we need all the evidence we can get. Read the whole article.

This is in the realm of speculation, but I’ve been wondering: what if, after the outbreak began, local officials panicked thinking this may be a human-“improved” virus that had escaped from the WiV, then calmed down once it became clear it was “only” another novel coronavirus. That would explain some of the skittish behavior in the very beginning, the destruction of samples,…  

ADDENDUM: yes, public health experts are undermining themselves by U-turning on recommendations for political expedience. 

And Insta snarks “nothing to see here, move along”: Parts of Beijing locked down due to fresh virus cluster

ADDENDUM 2: Israeli public health expert on what we might face in the winter