Piercing the MLS Is Back Bubble
/By Jamon Moore, Eliot McKinley, & Ben Wright
Viruses and Math are Hard
If there is one thing that 2020 has taught us so far, it’s that viruses are incredibly difficult to defeat, and that the math around them is difficult to calculate and convey -- much, much more difficult to create and understand than, say, an expected goals model in soccer. This is why months after COVID-19 emerged experts are still arguing over the data related to testing, cases, and hospitalizations, not to mention treatment options.
We are not epidemiologists, but we do like our data. While there probably should not be an MLS is Back tournament in Orlando starting this week, at this point there will be, and once again the math is causing problems for MLS. While MLS HQ fixed the issues with how teams advance out of groups, COVID-19 in the Disney World MLS bubble (The Bubble) is not solved so easily.
MLS has laid out detailed health protocols for all personnel involved in the Orlando tournament. Those traveling to Orlando must test negative on two Polymerase Chain Reaction (PCR) tests within 72 hours before traveling to Orlando. Upon arrival, players are tested again and remain in quarantine with gourmet room service dining options until a negative PCR is returned and training can begin. Additionally, MLS laid out a reasonable plan for isolation and contact tracing those who test positive in The Bubble. However, while MLS players and staff must remain in The Bubble, hotel employees are not confined within, given the Orlando area’s increasing COVID-19 rates, this could be a weak link that we will ignore for now.
The San Jose Earthquakes entered The Bubble on June 24. Santa Clara County, where Earthquakes (formerly Avaya) Stadium resides, had not allowed professional sports teams to practice together, and Matias Almeyda, desperate to get his team practicing, decided to go as soon as possible. In a conference call with Bay Area reporters ahead of departure, Tommy Thompson was quick to say that he felt confident the league had created a safe environment at the Walt Disney World Swan and Dolphin Resort outside the ESPN Wide World of Sports complex where the games will be held: “I think Don Garber [and] the league put in countless hours of ironing out the specific details in order to put us in the safest environment that we can be in. So, I trust in them, I trust what they’re doing. And I trust in our union as well...I’m comfortable with the decision I made; I’m comfortable with the decision our union made...and I think MLS has done a great job in making sure that we’re in a safe environment.”
Once the Earthquakes were inside The Bubble, Thompson and others reiterated their confidence in the environment. “I do feel safe.”, Thompson commented to national media back on June 26. “I think there’s been a ton of precautions that have been taken. We’ve already been tested twice, so it’s good to see there’s a process in place to protect us from the virus.” New Earthquakes center back Oswalo Alanis had similar comments after arrival, “I’m very happy. I feel really safe, and we are really protected with the protocols and all the things that the league and the tournament and the people [have] here. Everything is given care in the safest way.”
There is no inter-club contact, and this seems to have been mostly maintained so far. “As you walk around this bubble, every precaution is being taken -- from the meals to the testing to the sanitation, hand sanitizer in the hallways,” Philadelphia Union head coach Jim Curtin said to Jonathan Tannewald of the Philadelphia Enquirer on July 3. “I haven’t laid eyes yet on another team.” However, Chicago’s Djordje Mihailovic has indicated otherwise. Additionally, there is this chilling anecdote from Colorado’s Diego Rubio:
Let’s take a look at what we think we know about The Bubble:
As of July 4th, there have been 2752 total tests and 14 positives (0.5%) from scheduled testing, affecting three teams: FC Dallas (11), Minnesota United (one likely false positive), Columbus Crew (one), and Nashville SC (one and up to 4 more).
Each team is allowed 45 or 46 in their delegation.
Given the number of tests reported by the league on July 2, the delegation from the league and related staff appears to be roughly 270.
As of Friday, July 3rd, 15 teams were in The Bubble (about 675 people), with three more teams scheduled to arrive on Saturday and another two teams Sunday, following Colorado’s postponement.
That makes 945 total people in The Bubble, providing us with a 1.5% individual infection rate so far. If the four additional Nashville players are confirmed, it increases to 1.9%.
FC Dallas had an additional nine positives after further testing based on their two positives, including a coach. Their opening game with Vancouver has been postponed.
Teams are on their own floor in the resort.
No contact tracing for positive cases has linked players from different teams.
When should teams arrive into The Bubble and when are they arriving?
First, let’s talk about the COVID-19 PCR testing. PCR is a method to amplify a specific genetic sequence, in this case the genome of SARS-CoV-2, the virus that causes the COVID-19 disease. Samples are collected from the nasal cavity of a person and after some processing steps, a real time PCR protocol is utilized to measure SARS-CoV-2 genomic content in the sample.
Because a human doesn’t have any SARS-CoV-2 genetic code hanging out in their nasal cavity unless they are infected with the virus, you can be pretty sure (with more than 95% certainty) that a positive PCR test is indicative of true infection. MLS has reported a number of false positive tests, which is inevitable when you are running thousands of tests, but could also be indicative of issues with the testing protocol.
However, a negative test does not mean that you are not infected with SARS-CoV-2. The false negative rates, i.e. you have SARS-CoV-2 but the test says you don’t, are rather high, approaching 20%. This is primarily because of poor sample quality (the swab wasn’t collected or processed correctly) and the virus hasn’t had enough time to reach a level that is detectable. Kucirka et al. from Johns Hopkins conveniently published a paper that modeled the false negative rates based upon days after infection with SARS-CoV-2. For the first three days after infection, the likelihood of a false negative test is almost 100%, which quickly falls off to around 20% by 7 days after infection, although there are large variances on these numbers. For these reasons, testing is not a one-off thing. Monitoring must be consistent over a length of many days for a person to be sure that they remain SARS-CoV-2 free, which MLS appears to be doing in The Bubble.
Given the testing characteristics above, what are the chances that COVID-19 got into The Bubble from the outside? For this we make some assumptions:
False negative rates are those reported by the Johns Hopkins group
The population-level infection rate is 2.0%
Infections occurred the day prior to arrival into The Bubble, after the two in-market tests
Daily testing for all personnel
There is no spread once inside The Bubble
Our 2% assumption feels conservative given 0.88% of Americans have tested positive so far for COVID-19 (as of July 5th), and the CDC believes the actual infection rate may be ~10x that (8.8%). Additionally, this number is highly variable depending on what city a team is based in, and coincidentally 2% is very close to the 1.9% reported positive rate of COVID-19 imported into The Bubble so far.
A team entering on its own would be essentially in the clear of imported COVID-19 by 7 days after arrival into The Bubble. For increasing numbers of people entering The Bubble simultaneously the time is longer, but by 10 days any negative test would be a true negative. These timelines align decently well with the original MLS is Back Tournament guidelines mandating that teams arrive seven days before their first game.
However, as no plan survives contact with COVID-19, things haven’t quite gone that way as the tournament nears. True and false positives, symptomatic staffers, inconclusive tests, and testing delays have delayed team travel to Orlando, and there has been a staggered entry of teams into The Bubble. Toronto FC is scheduled to arrive July 6, only four days prior to their first match and not enough time for any newly infected personnel to reliably test positive.
When integrating the actual dates of arrivals of teams and personnel the picture gets cloudier. Assuming that approximately 270 league and broadcast personnel entered The Bubble on June 23, an initial spike of false positives tests were likely to be seen given our assumptions. In fact this did not happen, only two positives were detected on the June 28th reporting date, indicating that the population rate of infection of those entering the bubble was likely much less than 2%. The real test will come over the next few days, after a large number of teams have entered The Bubble. The highest likelihood of false negatives will be today (July 6th), after which it rapidly decreases. Any imported infections would likely be detected shortly after this. By July 11th any positive tests can be assumed to have been acquired in The Bubble. That so far only 14 people have tested positive is a credit to the teams for keeping their players largely infection-free while at home. By our modeling there could be upwards of 59 potential false negative tests in a worst case scenario at this point.
Based on this information, and the arrival dates of team delegations, we can reasonably conclude that all but the Minnesota United positive test have come from outside The Bubble as of time of publication. And it’s quite possible (between 20% and 40%) that positive also came from infection outside The Bubble depending on the actual infection day which contract tracing may or may not be able to determine.
Based on this analysis, it will take eight or nine days to ensure safety in a bubble scenario of more than a few teams. This matches up with the seven days recommended by one infectious disease expert when the Columbus Dispatch reported that a friendly was planned between the Crew and Minnesota United on July 5th that was sensibly cancelled. The recommendation here is to reset the clock for inter-team activities any time a positive is found. It’s worth noting MLS initially proposed a two week period in Orlando to test personnel before the tournament, but negotiations with MLSPA shortened that period to a mandatory seven days. That period has now been shortened for several teams, as complications with testing delayed their initial travel plans. This presents a heightened risk for importation of COVID-19 into The Bubble, which MLS seems to be ok with.
Suppose a player is infected in a tournament game -- what then?
Given the staggered game schedule approach, if it is determined in post-game testing a player had a previous false negative and was likely infected while playing a game, it will create a complicated situation for everyone involved in that game. European leagues have seemingly avoided in-game transmission so far, but there is much even infectious disease experts don’t know about the potential for in-game transmission between athletes. While we don’t know the details of the FC Dallas situation, that may be a warning sign droplets from heavy breathing in practices and games can carry the virus to many players and others near the pitch (this Johns Hopkins Health article says COVID-19 cannot be transmitted through sweat), although experts are divided on the amount of exposure that is needed.
Once a new positive is found, the data suggest that the tournament should be suspended for those teams, the referees, and others who came in close contact, until sufficient time passes to ensure safety in another match. At that point, is there still a tournament? Do those teams need to withdraw? Can the schedule be elongated to allow for proper time to pass for testing? This is where the television contracts and revenues will probably dictate the limited options available to the league, but such an analysis should have been completed ahead of the event scheduling. There is no forced timetable to start or end this tournament, except as determined by the money associated with it.
Given the league and MLSPA didn’t have teams create individual bubbles ahead of their arrivals, the only reasonable option that ensures participant safety is to extend the schedule by a week between each team’s games as soon as the first in-game transmission is discovered, and be prepared for the potential to lose officials and other gameday league staff to quarantine, if not to more infections.
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At the end of the day, we’re living through an unprecedented pandemic. Things are unpredictable. Any attempt to resume professional sports will be less than ideal. Leagues and owners will have to balance their desire for revenue with the safety of players, staff, and their families. There are legitimate questions about the integrity of The Bubble in Orlando, and questions will continue to be asked as players and staff continue to test positive in The Bubble.
There’s a larger issue of if the tournament should proceed at all and if playing a tournament in a state where cases continue to skyrocket is a wise (or ethical) option at all. What we can say is, based on the model laid out above, having teams on site for eight or nine days before playing a match is a reasonable guarantee that cases will be weeded out and dealt with before the tournament kicks off. That was MLS’s plan initially. That plan has gone out the window now, with several teams arriving just days before their first match and players only quarantining in their rooms for 12 hours! What happens now will be a test of the league’s protocols to identify and contain cases that appear in The Bubble, which has already been questioned. The Bubble is already compromised. Now the priority is damage limitation.
In conclusion: wear a damn mask, everyone.