I don’t know why the discussion is being limited to the R0 being 0.90 or 0.95. Is it not plausible — indeed, likely — that the R0 might be 1, 1.1, 1.2 or even much higher? Anything above R0=1 would imply a cascade of transmission events that would result in far more deaths than any figures these analyses are showing, and it seems reasonable to be very concerned about that even if these transmission chains are stopped or burn out at some point in the near future.
R0 could certainly be much higher in principle, though if it is, it doesn’t seem to be reflected in the number of positive cases being recorded in the US—which has been holding steady or slightly declining for the past month—or the number of deaths (declining, although there would be a lag there). These indicators could be misleading of course—the US, like the UK, is nearly certainly undertesting and undercounting cases. However, the number of tests has been going up, and if the number of cases being ‘caught’ isn’t increasing this is some indication that R0 is somewhere a little below 1. So I would tentatively agree with the OP’s suggestion here.
One reason looking at different assessments based on R0=0.9 is informative is that it illustrates just how high the uncertainty and room for error is in these sorts of analysis. The OP predicts 75,000 deaths as a plausible possibility; Bedford predicts 150-600/day, so 2,100 −8,400 over the course of 2 weeks of protests (assuming each day carries the same impact on R0, which is probably wrong); both using R0=0.9 as a central assumption, and recognising that the present R0 is a key factor. Because present value of R0 is such a critical factor, comparing different estimates at the same R0 makes it easier to compare/contrast.
One of my personal concerns is that the BLM protests may end up unduly scapegoated (in terms of their role being overestimated) for any increase in cases and deaths; the US administration has done quite a bit of scapegoating already in my view, and there are many ways in which its own response has been far from adequate. My intuition is that other aspects of states reopening prematurely are likely to play a bigger impact in a possible second wave. If there were a significant overestimation of the impact of the BLM protests for example, this would be bad not only for the BLM movement and antiracism in the US; it would also be bad in terms of understanding the other causes of increase of R0 and putting in the appropriate planning overall for preventing and responding to future waves. (Likewise however, if those of us who think the impact of the protests is lower than in reality are wrong, it would be good to update).
I’m not convinced that we would have already seen a significant uptick in reported/confirmed case numbers quite yet (weren’t the largest protests this past Saturday?). The median incubation period is ~5 days, most people don’t get tested at the time of symptom onset, and the PCR test turnaround time still seems to still be at least a day or two. Perhaps most importantly, most of the protestors seem to be relatively young and so many may be asymptomatic or may have mild cold/flu-like symptoms. I’m more interested in (and concerned about) any secondary transmission events that may involve older family members that protestors might live with/come into contact with. Many of these older folks would presumably have more serious symptoms and so would be more likely to show up in confirmed cases/hospitalizations data over the coming weeks.
I think perhaps the most informative case for the determining the effect of protests on overall transmission might be New York City. In recent days it has been at record lows in terms of confirmed cases/hospitalizations/test positivity rate, it has one of the highest number of tests per capita of any state/country, it has seen large protests, and it is has not reached the phase of reopening that involves activities known to be high risk (for now, it’s just construction/manufacturing and curbside pickup — no schools, dining in restaurants, bars, etc.). I’m keeping an eye on this Metaculus question (which has already been mentioned elsewhere): https://pandemic.metaculus.com/questions/4590/how-many-confirmed-new-covid-19-cases-per-day-will-there-be-in-new-york-city-for-the-week-of-june-15th-to-june-21st/
As for scapegoating, I agree that it’s likely and it’s extremely unfortunate. I think few (if any) of us would disagree that this is a just cause. But it is nevertheless concerning that there are mass gatherings in the middle of a pandemic, whatever the reason for them might be. A big concern of mine is that the credibility of messaging by the public health community may have taken a huge hit. Many public health professionals were (rightly) telling everyone to stay home as much as possible and then seemingly disregarded their own advice to participate in/support the protests. If (in my view, when) a second wave comes, will public health messaging to again stay home be viewed through a far more partisan lens than has already been the case?
I’m not convinced that we would have already seen a significant uptick in reported/confirmed case numbers quite yet (weren’t the largest protests this past Saturday?). The median incubation period is ~5 days, most people don’t get tested at the time of symptom onset, and the PCR test turnaround time still seems to still be at least a day or two. Perhaps most importantly, most of the protestors seem to be relatively young and so many may be asymptomatic or may have mild cold/flu-like symptoms. I’m more interested in (and concerned about) any secondary transmission events that may involve older family members that protestors might live with/come into contact with. Many of these older folks would presumably have more serious symptoms and so would be more likely to show up in confirmed cases/hospitalizations data over the coming weeks.
Right. But with regard to R0 =0.9, I understand R0=0.9 was being used as the background R0 prior to the impact of the protest, rather than the R0 following the impact of the protests (if ‘background’ R0 is <1, then the impact of an R0-increasing event/set of events will have a lesser effect than if ‘background’ R0 is >1). It may be the case, as you suggest, that R0 has increased significantly since the start of the protests until now (whether due to the protests or in combination of other factors), in which case protests right now are happening against a higher R0 than these estimates assume—but we don’t have the data. I agree that NYC will be interesting.
In an earlier Twitter thread, Trevor Bedford says “my rough guess would be that an infected individual would on average transmit to one further individual each day in the protest setting” — so I think he was using 0.9/0.95 as the R0 to estimate the impact of the protests. https://twitter.com/trvrb/status/1269395234762285056 But I don’t think this is a safe assumption and I’m concerned that the R0 might be significantly higher than ~1 in a mass gathering.
I don’t know why the discussion is being limited to the R0 being 0.90 or 0.95. Is it not plausible — indeed, likely — that the R0 might be 1, 1.1, 1.2 or even much higher? Anything above R0=1 would imply a cascade of transmission events that would result in far more deaths than any figures these analyses are showing, and it seems reasonable to be very concerned about that even if these transmission chains are stopped or burn out at some point in the near future.
R0 could certainly be much higher in principle, though if it is, it doesn’t seem to be reflected in the number of positive cases being recorded in the US—which has been holding steady or slightly declining for the past month—or the number of deaths (declining, although there would be a lag there). These indicators could be misleading of course—the US, like the UK, is nearly certainly undertesting and undercounting cases. However, the number of tests has been going up, and if the number of cases being ‘caught’ isn’t increasing this is some indication that R0 is somewhere a little below 1. So I would tentatively agree with the OP’s suggestion here.
https://www.worldometers.info/coronavirus/country/us/
One reason looking at different assessments based on R0=0.9 is informative is that it illustrates just how high the uncertainty and room for error is in these sorts of analysis. The OP predicts 75,000 deaths as a plausible possibility; Bedford predicts 150-600/day, so 2,100 −8,400 over the course of 2 weeks of protests (assuming each day carries the same impact on R0, which is probably wrong); both using R0=0.9 as a central assumption, and recognising that the present R0 is a key factor. Because present value of R0 is such a critical factor, comparing different estimates at the same R0 makes it easier to compare/contrast.
One of my personal concerns is that the BLM protests may end up unduly scapegoated (in terms of their role being overestimated) for any increase in cases and deaths; the US administration has done quite a bit of scapegoating already in my view, and there are many ways in which its own response has been far from adequate. My intuition is that other aspects of states reopening prematurely are likely to play a bigger impact in a possible second wave. If there were a significant overestimation of the impact of the BLM protests for example, this would be bad not only for the BLM movement and antiracism in the US; it would also be bad in terms of understanding the other causes of increase of R0 and putting in the appropriate planning overall for preventing and responding to future waves. (Likewise however, if those of us who think the impact of the protests is lower than in reality are wrong, it would be good to update).
I’m not convinced that we would have already seen a significant uptick in reported/confirmed case numbers quite yet (weren’t the largest protests this past Saturday?). The median incubation period is ~5 days, most people don’t get tested at the time of symptom onset, and the PCR test turnaround time still seems to still be at least a day or two. Perhaps most importantly, most of the protestors seem to be relatively young and so many may be asymptomatic or may have mild cold/flu-like symptoms. I’m more interested in (and concerned about) any secondary transmission events that may involve older family members that protestors might live with/come into contact with. Many of these older folks would presumably have more serious symptoms and so would be more likely to show up in confirmed cases/hospitalizations data over the coming weeks.
I think perhaps the most informative case for the determining the effect of protests on overall transmission might be New York City. In recent days it has been at record lows in terms of confirmed cases/hospitalizations/test positivity rate, it has one of the highest number of tests per capita of any state/country, it has seen large protests, and it is has not reached the phase of reopening that involves activities known to be high risk (for now, it’s just construction/manufacturing and curbside pickup — no schools, dining in restaurants, bars, etc.). I’m keeping an eye on this Metaculus question (which has already been mentioned elsewhere): https://pandemic.metaculus.com/questions/4590/how-many-confirmed-new-covid-19-cases-per-day-will-there-be-in-new-york-city-for-the-week-of-june-15th-to-june-21st/
As for scapegoating, I agree that it’s likely and it’s extremely unfortunate. I think few (if any) of us would disagree that this is a just cause. But it is nevertheless concerning that there are mass gatherings in the middle of a pandemic, whatever the reason for them might be. A big concern of mine is that the credibility of messaging by the public health community may have taken a huge hit. Many public health professionals were (rightly) telling everyone to stay home as much as possible and then seemingly disregarded their own advice to participate in/support the protests. If (in my view, when) a second wave comes, will public health messaging to again stay home be viewed through a far more partisan lens than has already been the case?
Right. But with regard to R0 =0.9, I understand R0=0.9 was being used as the background R0 prior to the impact of the protest, rather than the R0 following the impact of the protests (if ‘background’ R0 is <1, then the impact of an R0-increasing event/set of events will have a lesser effect than if ‘background’ R0 is >1). It may be the case, as you suggest, that R0 has increased significantly since the start of the protests until now (whether due to the protests or in combination of other factors), in which case protests right now are happening against a higher R0 than these estimates assume—but we don’t have the data. I agree that NYC will be interesting.
In an earlier Twitter thread, Trevor Bedford says “my rough guess would be that an infected individual would on average transmit to one further individual each day in the protest setting” — so I think he was using 0.9/0.95 as the R0 to estimate the impact of the protests. https://twitter.com/trvrb/status/1269395234762285056 But I don’t think this is a safe assumption and I’m concerned that the R0 might be significantly higher than ~1 in a mass gathering.
In any case, the most reliable modeling I’ve seen (and that Trevor cites) estimates that the current overall background R0 in the U.S. is already back above 1. :/ https://covid19-projections.com/#current-us-projections
Thanks Juan, I hadn’t seen that most recent R0 estimate you link to—concerning.