A thread about COVID-19, asking young people including US college students to please stay home despite all the temptations and the low mortality rate for young people so far.
One person I know has already died and now at least 4 are sick because of transmission at a duplicate bridge club in my home town. This thread shows data from a study of transmission in a mall in China.
This is from a study published in Emerging Infectious Disease on March 12, 2020. The authors studied a chain of transmission in Wenzhou, China (which is not in the Wuhan quarantine area).
In the below image, each dot is a person who caught COVID-19. They are shown on a grid. The X axis of the grid is the floor of a shopping mall. For example, 7 is the 7th floor of the mall, while B1 is basement level 1. 
The dots are different colors to indicate whether the people were staff sharing the same office (orange), other staff (red), customers (green), or patients who caught the infections outside the building (purple).
The X axis is the calendar days of January and some of February, so the image also shows the timing of transmission.
The reason this study is published in EID is shown by the lines connecting the dots. Many of the dots are connected by a line, those people had "close contact."
Close contact is defined as being within 6 feet (2 meters) of someone for a prolonged period of time (hours each day), such as when living with or sharing an office with someone. Close contact also includes getting coughed or sneezed on.
Many of the dots are connected by close contact lines. But, many of them are not. For example, I, J, K, L, O, Q, R, S, T etc. are not connected to any other dots by close contact.
The interpretation of this study is that COVID-19 can be spread by "fomites" (contaminated surfaces) or by aerosols suspended in the air, in a public setting like a mall.
The next picture shows the timeline in more detail.
This figure shows the patients in this mall-associated cluster on the Y axis . They people on the Y axis are color-coded as in panel A but then the color scheme changes as you move from left to right, to show different parameters.
The Y axis is again time, from part of December through part of February. Yellow shows the potential incubation period, while the different shades of orange show when someone had symptoms. Light orange means symptoms without fever, while dark orange means symptoms including fever
Patient A is the only one who had been in Wuhan; they left Wuhan on December 18 and didn't get symptoms until January 14. Now let's look at Patient O, the first customer. They went to the mall on January 18.
Patient O developed symptoms (with fever, dark orange) on January 21, leading to an asymptomatic incubation period of 3 days.
They shut the mall down on January 22. 34 people got COVID-19 because of a chain of transmission that started at this one mall.
The estimated average number of people infected by a single person is as high as 4, with a range of 1.4-4.0. This calculation comes from other kinds of data. Please stay home, friends. Please just stay home, even if you are in the age range where COVID probably won't kill you.
The other thing I want to point out is that among these 35 people, 6 had respiratory symptoms but not fever before they got a fever, and one never got a fever at all. It is unutterably stupid that in #ColoradoSprings they are testing only people who have fever. @denverpost
Someone I know at the local duplicate bridge center has already died; there is probably a cluster at the bridge club just like this one at the mall. At least one person from the bridge center with symptoms but not a fever has been denied testing.
I know three other people in #ColoradoSprings who have symptoms but not fever and they were denied testing. @csindependent @csgazette People in Colorado Springs are probably going to die because of a lack of testing capacity and the policy of testing only people w fever.
@ACBLbridge please read my thread about COVID-19 and the Colorado Springs bridge club.
@threadreaderapp please unroll
Here is the citation, btw: wwwnc.cdc.gov/eid/article/26…
Indirect Virus Transmission in Cluster of COVID-19 Cases, Wenzhou, China, 2020, by Cai et al.
Indirect Virus Transmission in Cluster of COVID-19 Cases, Wenzhou, China, 2020, by Cai et al.
Y axis, dang it.
X axis. dang it. scicomm fail
