The Simple Math of Group Coronavirus Risk.
Update: The County of Orange (California) Health Officer has issued an order this afternoon banning any social events, public or private, except for families or living units. It also bans contact closer than six feet, other than family. Essential services are exempt. This lasts until March 31 at least. And I hadn’t even written this article yet.
First of all, I am not a doctor or an epidemiologist. These are just simple ideas. I was motivated because a reporter asked Dr. Fauci how more dangerous was a group of 25 over a group of 10. He didn’t reply. So here are some considerations.
First, if you are in a group of ten in a confined area for a length of time, how do you interact with these people? If you are all in an audience separated by six feet, not only side to side, but front to back, you may be okay. Six feet is not just skipping a single seat. If you have people sitting in front and back, and on both sides, your risk has increased by at least a factor of 5. If your diagonal neighbors are coughing or sneezing, you could be in for a perfect 9 fold increase.
If you are playing bridge with three others who are breathing toward each other for two hours, and all handling the same cards, day after day or week after week, your risk has increased by a factor of four.
In a group of 10 which is not spread out, how are you seated? If the 10 are at a long board table that is also wide, a rare occurrence, your risk is only tripled by the two people beside you. If it is a narrow table, count two next to you and three across from you to make five and a six fold increase in risk.
If the group of 10 is in a mixer, and you talk to 5 members face to face, it is a sixfold increase of risk. If you are a super mixer and talk to all people there, including shaking their hands, tenfold increase in risk.
Welcome to the group of 25. If well separated in a class, no risk increase. If closest packed, possibly a factor of 5 or 9 again. If it is a mixer, and you talk to five people for more than a minute, assuming you don’t shake hands with anybody else, a risk factor of 6. Now, assume everybody else at the party acts the same. Then, the total connections in the room is 5×25 = 125. So if there were only 1 infected spreader, they contact 5. But, unless this is back to cliquish high school, each of them contacts 5 others. However, the virus is considered passible only from day 3 on. Since the 5 new virus cases haven’t had it for more than an hour, they will not pass it orally. On the other hand, if they shook hands with the virus vector, that would eventually rub off on all 25 people. Bingo! So the risk is increased by 25 for each person, so the total risk increase is 25 squared, or 625! If they all stayed home, risk is nil for everybody. They can still communicate by Zoom, or other software or methods. The virus does not infect, nor does it pass on by electrons.
So the answer to Fauci’s question for a party of 10 versus 25 with gladhanders like Trump, could be 100 versus 625. With only 5 meetings for each person, it is 6×10 = 60, or 6×25 = 150. Math kills!
Back to the bridge players, or other four person games. Since there is a fourfold increase or risk for four people, the number of risk-person increases is 4×4 = 16.
Younger people have to stop partying for a few weeks, isolate, and let the virus die out. Even young people can get lung damage from the virus, lasting up to a year. Students could get behind in classes. Employees could be laid off for weeks, or months if we don’t end it. Sanjay Gupta of CNN said that 40%-60% of Americans could be infected, with a mortality of 1% to 2%. We all have to work together, and take this very seriously.
