Super-spreader Situations

[audreyh1]

Contact tracing seems to be working in some states and providing useful statistics:

From Maryland, where contact tracers found 44% of people who tested positive for the virus had recently attended family gatherings:

CONTACT TRACING DATA. In addition to identifying individuals who may have been infected with COVID-19, Maryland is now using contact tracing data to find patterns of behavior, and to identify where and how the virus is spreading. The governor announced the following findings based on recent interviews conducted with COVID-19 patients:

Higher-Risk Gatherings (Percentage of Interviewed Cases):
Family Gatherings – 44%
House Parties – 23%
Outdoor Event – 21%

Higher-Risk Locations (Percentage of Interviewed Cases):
Work Outside the Home – 54%
Indoor/Retail Shopping – 39%
Indoor Dining at Restaurant – 23%
Outdoor Dining at Restaurant – 23%

Employment Information (Percentage of Interviewed Cases):
Health care – 25%
Other – Non-public Facing – 23%
Other – Public Facing – 13%
Restaurant/Food Service – 12%

https://governor.maryland.gov/2020/...wide-mask-order-out-of-state-travel-advisory/

 

[MichaelB]

Thanks for the link. Family gatherings as the biggest source is no surprise. Similar conclusions from the early Asian reports.

 

[audreyh1]

There are probably tons of these:

A NC family gathering of 2 dozen folks with no precautions resulted in 14 infections which then spread further:

This set into motion a person-to-person contact chain that to date has spread COVID-19 to 41 people in 9 different families and 8 different workplaces,” McCracken said.

Family gathering infects 41 people with the coronavirus, NC health official says
https://www.charlotteobserver.com/news/coronavirus/article244147427.html

 

[athena53]

I was unpleasantly surprised at the results for outdoor dining and events. Up to now I'd considered outdoor dining less risky- in fact, the B&B where we stayed 2 weeks ago served all meals outdoors (with distancing, servers wore masks). I suppose "outdoor events" can cover a lot- a church service of 30 people, distanced with masks, or a beach volleyball tournament.

 

[The Cosmic Avenger]

I was unpleasantly surprised at the results for outdoor dining and events. Up to now I'd considered outdoor dining less risky- in fact, the B&B where we stayed 2 weeks ago served all meals outdoors (with distancing, servers wore masks). I suppose "outdoor events" can cover a lot- a church service of 30 people, distanced with masks, or a beach volleyball tournament.

Same, I found that alarming, as I've felt outdoor exposure was somewhat safer. I wonder how many of those cases were caught from a dining companion, who will usually be < 6 feet away and unmasked for a while when eating, vs. other diners or servers.

 

[Aerides]

I think the proximity + mass + time factors overrides the environment.

You can be inside with 2 people @ 8feet for an hour, probably safer than you can be outside in a group of 20 mingling and talking and hugging and chatting for 2 hours.

Similarly, "outdoor dining" for me means me +1, well spaced from others, only briefly interacting with our server. It doesn't mean Party of 12.

 

[audreyh1]

They are obviously not distinguishing between outdoor activities with or without masks and social distancing. So that makes it a bit hard to judge. The more specific case studies reported now and then seem to indicate that often there are no precautions taken at the family gatherings.

Here is an interesting graphic showing the spread from the NC study where no precautions were taken at the initial family gathering of ~24.

This probably tells a typical story!

You feel bad for all those co-workers!

Notice how in family B, the 9 year old child spread it to both grandparents. All the other spreading came from adults.

 

[sengsational]

I'd like a deep dive into the specifics of the outdoor and retail cases because those are activities I presumed were at least kind of safe-ish. I have been to a few outdoor "house party" type events, but with just a few people, and life cannot be sustained without a hardware store visit or two, but always with an N95 and fomite precautions.


If the data was collected with a form like "Which of these activities did you do in the last 14 days? (select zero one or more): went to work, indoor shopping, outdoor eating, indoor eating, etc, then I'm less worried about this report. My reasoning (warning, he's thinking again), if the subject was not being particularly careful, a lot of checkboxes would get checked. That doesn't mean each of the check boxes are equally likely to have been the transmission point.

 

[Chuckanut]

I think the proximity + mass + time factors overrides the environment.

You can be inside with 2 people @ 8feet for an hour, probably safer than you can be outside in a group of 20 mingling and talking and hugging and chatting for 2 hours.

Similarly, "outdoor dining" for me means well spaced from others, only briefly interacting with our server. It doesn't mean Party of 12.

+1

A party of twelve crowded into one or two outdoor picnic tables and/or circulating about at close distances is not my idea of outdoor dining done safely. The big advantage of any outdoor activity is the ability of the air currents to dilute the virus. Crowding together at a picnic table works against good air circulation. I suspect that we would have also seen a lot of sharing of serving utensils, physical touching, and face-to-face up-close chatting. We need to see the movie, not just the snapshot.

People must constantly practice safety. Not only at crowded events, but daily even when only a few people are near us. Sadly, staying away form others still the safest thing to do.

Safety is a habit.

 

[tb001]

The outdoor dining concerns me too. We have not been going out to eat at all because the safety of outdoor dining experiences seem to vary depending on where it is. Some places are just too crowded.

Our area has been shut down for indoor dining for several weeks, but we are still having the majority of new outbreaks linked to restaurants/bars. I had assumed this was due to employees testing positive, but now I’m wondering.

 

[audreyh1]

I'd like a deep dive into the specifics of the outdoor and retail cases because those are activities I presumed were at least kind of safe-ish. I have been to a few outdoor "house party" type events, but with just a few people, and life cannot be sustained without a hardware store visit or two, but always with an N95 and fomite precautions.


If the data was collected with a form like "Which of these activities did you do in the last 14 days? (select zero one or more): went to work, indoor shopping, outdoor eating, indoor eating, etc, then I'm less worried about this report. My reasoning (warning, he's thinking again), if the subject was not being particularly careful, a lot of checkboxes would get checked. That doesn't mean each of the check boxes are equally likely to have been the transmission point.

They mention interviews, so who knows how the data is organized, but it is the contact tracers collecting it FWIW.

 

[Rianne]

I can't seem to find information about when one would test positive after infection. Hypothetically, I was near someone who tested positive yesterday. She/he transmitted Covid to me yesterday. When would I test positive?

Our county has a test turnaround time of 24/48 hours. Our numbers are skyrocketing. We were in a bubble, very few cases until recently (the last 14 days). Now the line to get tested is very long, everyday. We live near the testing site and I drive by there at least once a day.

I understand the load of transmission varies. And once infected there's nothing one can do to stop the symptoms or lessen the severity, that I"m aware of.

 

[Ready]

I went to an outdoor restaurant recently for the first time since March. I used to eat in restaurants several times a week so losing that has been difficult. But I did not feel completely comfortable being there. The tables were spread out but it was still a lot of people to be around for a couple of hours. And there is nothing you can do to avoid the waitress and cook staff handling your dishes, glasses and silverware.

It does not completely surprise me that outdoor dining is not as safe as we thought it was. I’m going to avoid eating in restaurants for the time being.

 

[GravitySucks]

I can't imagine the outdoor dining I've done is any less safe than getting take out.

Two or three people to a table, same people as I would have eaten with at home. Tables were a minimum of 8 feet apart. Nice breeze. Server was masked and just delivered the food that was ordered at the counter.

 

[audreyh1]

I imagine there are ways to do outside dining safely, and not safely.

If people from different households are getting together to eat at a table, removing masks to eat, and talking while masks are off, that can be a problem even if outside.

 

[The Cosmic Avenger]

I can't imagine the outdoor dining I've done is any less safe than getting take out.

Two or three people to a table, same people as I would have eaten with at home. Tables were a minimum of 8 feet apart. Nice breeze. Server was masked and just delivered the food that was ordered at the counter.

Yep, exposure = concentration x time. So a shorter time indoors where there might be more of the virus could be the same exposure as being outdoors around other people for a longer time. But you rarely if eve know who has it, and what concentrations might be in the air, so I try to minimize all exposure, and the rare times I'm indoors (other than at home) I make it as fast as possible and wear an N95 mask.

 

[JoeWras]

Like everything else, some of the businesses are respecting the distancing outdoors more than others. I've seen way too much crowding outdoors. I should have taken a picture of what I saw last week near the NC coast. People just jammed in outdoors. We ended up leaving and ordering pizza.

 

[RAE]

Good article in the Atlantic today about super-spreader situations. If interested, here is the link:

https://www.theatlantic.com/health/..._content=20200730&silverid=NTEwNDAwMTI2MjY4S0

Quote from the article:

Saskia Popescu, an infectious-disease epidemiologist, emphasized to me that we should not call these “super-spreaders,” referring only to the people, but “super-spreader events,” because they seem to occur in very particular settings—an important clue. People don’t emit an equal amount of aerosols during every activity: Singing emits more than talking, which emits more than breathing. And some people could be super-emitters of aerosols. But that’s not all. The super-spreader–event triad seems to rely on three V’s: venue, ventilation, and vocalization. Most super-spreader events occur at an indoor venue, especially a poorly ventilated one (meaning air is not being exchanged, diluted, or filtered), where lots of people are talking, chanting, or singing. Some examples of where super-spreader events have taken place are restaurants, bars, clubs, choir practices, weddings, funerals, cruise ships, nursing homes, prisons, and meatpacking plants.

 

[audreyh1]

Thanks - very good article! Great overview of droplets versus aerosols and terminology that sometimes seems to have the WHO and other disease experts talking past each other. Clearly there is also some old versus new think going on as well.

To me “Super Spreader Event” implies one discrete gathering, like “XYZ turned out to be a super spreader event”, which is why I chose Super Spreader Situations to indicate the common environments in which COVID-19 seems to be so successfully contagious. But I see that the article uses that term for situations/environments. I almost titled this thread “Super Spreader Events” but that sounded like some things that had already happened.

 

[audreyh1]

I had to copy this post from another Covid thread. Talk about a super spreader event! This CDC report was just released.

SARS-CoV-2 Transmission and Infection Among Attendees of an Overnight Camp — Georgia, June 2020

260 of 344 individuals who were tested following a summer camp were found positive - 76%! This included a large number of children. Trainees and staff had been there a week, then were joined by the young campers the following week. There were 597 attendees total. Some steps had been taken to avoid spread, but not all the recommendations. All trainees, staff members, and campers had to provide documentation of a negative viral SARS-CoV-2 test ≤12 days before arriving.

From a tweet I just saw: "NEW from CDC: COVID19 outbreak at an overnight camp in Georgia infects *at least* 260 campers & staff. -51% of positives 6-10yo -44% 11-17 yo -Camp required a test <12 days before arriving & attempted "pods" -Masks required for staff but NOT campers"

Source (CDC): https://www.cdc.gov/mmwr/volumes/69/wr/mm6931e1.htm?s_cid=mm6931e1_w

This virus keeps demonstrating that given the right environment/situation, it is just unbelievably contagious.

 

[sengsational]

I think that demonstrates that a test that's done too many days ago is not very effective at limiting the spread. This is exactly the kind of thing that was elucidated in Dr. Mina (et al) analysis in https://www.medrxiv.org/content/10.1101/2020.06.22.20136309v2

You need to test immediately before the gathering. It's not perfect, but much better than a very accurate test a couple weeks in advance, as proven by the math in the paper.

 

[JoeWras]

I think that demonstrates that a test that's done too many days ago is not very effective at limiting the spread. This is exactly the kind of thing that was elucidated in Dr. Mina (et al) analysis in https://www.medrxiv.org/content/10.1101/2020.06.22.20136309v2

You need to test immediately before the gathering. It's not perfect, but much better than a very accurate test a couple weeks in advance, as proven by the math in the paper.

Yeah, imagine your security check at the airport. What if they allowed you to do it anytime in the previous 5 days? And you can go home for a while after your security check then just walk on the plane the day of departure.

Same concept. An early test is basically useless.

 

[omni550]

It seems as though there may be a typo/error in the percentages shown in red below, as the total for that group is 139%. My initial guess is there's a glitch in the dining numbers as they are both 23.

Without access to the original data, it's not possible to determine what the correct values should be. Heck, I'd want to review ALL the numbers to verify.

Higher-Risk Locations (Percentage of Interviewed Cases):
Work Outside the Home – 54%
Indoor/Retail Shopping – 39%
Indoor Dining at Restaurant – 23%
Outdoor Dining at Restaurant – 23%

omni

 

[EastWest Gal]

Our next door neighbor has a college age daughter and two high school age sons. For the last two days there have been several cars parked in front of our house, including a car blocking the mailbox. I finally got them to move the cars to in front of their house. So apparently there is a prolonged visit going on next door. Mom works in a hospital.

The level of stupid is amazing.

 

[audreyh1]

It seems as though there may be a typo/error in the percentages shown in red below, as the total for that group is 139%. My initial guess is there's a glitch in the dining numbers as they are both 23.

Without access to the original data, it's not possible to determine what the correct values should be. Heck, I'd want to review ALL the numbers to verify.

Higher-Risk Locations (Percentage of Interviewed Cases):
Work Outside the Home – 54%
Indoor/Retail Shopping – 39%
Indoor Dining at Restaurant – 23%
Outdoor Dining at Restaurant – 23%

omni

It can be simply explained by people engaging in more than one activity.