Pac-12 football: USC’s positive cases, and testing trouble, a lesson for other programs

The Pac-12 season was a series of cautionary tales, but the final episode got us doing a triple shot here at Hotline headquarters.

Last week, USC announced four positive COVID-19 cases, which was both surprising and expected.

Expected, because Los Angeles goes through 5,000 new cases a day and the USC is an urban campus right in the middle of the inferno.

Surprisingly, because the Trojans – and UCLA – have done a remarkable job navigating the pandemic and keeping their players safe.

The Trojans run eight tests per week (six antigen, two PCR) and are as transparent as any program in the conference in terms of sharing relevant results.

The first of several press releases issued by the athletics department last week – all leading to a canceled game against Colorado – provided details of USC’s first positive of the season and gave the Hotline plenty to think about:

“We were told last night that a single footballer tested positive for COVID-19 on Monday 23 November.

“That person had traveled with us to Utah for Saturday’s football game, and had tested negative three times within 36 hours of travel and again on match day.

“All other test results on Monday were negative … The person is symptomatic and has been quarantined.”

Think about that for a moment:

Three negative tests for 36 hours prior to travel, one negative on matchday, and then positive and symptomatic by Monday – which probably means the player was symptomatic by Sunday afternoon or evening.

The amount of virus that can be detected by testing usually precedes the amount of virus needed for symptoms by 24 to 48 hours.

Still, the USC player repeatedly tested negative through Thursday, Friday and Saturday mornings… and was symptomatic by Sunday evening thereafter.

If he had been tested a few hours later, he might have turned up.

Regardless, that’s a narrow window for him to have turned positive – narrow enough that I wondered if the Trojans had been hit with a false negative:

Could the player have really been positive on Saturday morning while the game day tests were running?

The Hotline turned to an expert who helped us during the pandemic: Dr. George Rutherford, an epidemiologist, biostatistician and the director of UCSF’s Public Health Group.

Here’s the test cadence for the USC player:

Thursday morning: antigen test / negative Thursday morning: PCR test / negative (result available Friday) Friday morning: antigen test / negative Saturday morning: antigen test / negative Sunday: no test Monday morning: symptomatic and positive

So we asked Rutherford about the possibility of a false negative on game day – an antigen test allegedly performed by SafeSite, the Pac-12’s third-party testing operator.

Rutherford was skeptical of the theory, citing the likely point of infection on Wednesday.

With that, like Day Zero, Rutherford explained, the player would have turned positive on day three – Saturday – via the ultra-sensitive PCR testing technology.

But PCR tests typically require a 24 hour turnaround time and are not feasible on game day. The conference on Saturday uses fast-response antigen tests, but they are less sensitive.

Rutherford estimated that the player’s antigen test would have turned positive late Saturday or sometime on Sunday (day four), with symptoms by Monday (day five).

“This is a pretty standard timeline,” he added.

Our takeaway: The Pac-12 tests more than any conference in the country, but the Cadence can still be vulnerable to infections through the week.

If a player becomes infected on Wednesday, he will likely remain negative through late week and pre-game testing, but may become positive – and contagious – on Saturday afternoon, evening, or night.

For road teams testing late morning or early afternoon and then playing night games and flying home, this is particularly risky.

With a Wednesday infection, the test day might be too early; the test on Monday morning may be too late.

The closer the pregame tests start, the better – that of course depends on the turnaround time that SafeSite requires.

Taking it a step further: teams should consider testing the tour group on Sunday, back on campus.

Until now, Sunday has been a test-free day, because players are free.

But the conference’s official protocol states, “Daily point-of-care tests on every day of full exercise, higher risk of transmission activity, travel and games.”

Technically, Sunday could be viewed as a day of “higher risk transmission activity” as flights home after night are always in the early hours.

Yes, it is another burden on football program infrastructure. But theoretically, it would close a broadcast window on Sundays, when players gather outside of football activities.

And if a player tested positive, it would be possible to track down direct contact than if the teams were waiting for the tests on Monday.

USC was unlucky with the timing of the positive, but might have been lucky with the damage:

As far as we know, no infections have been found on that player, suggesting he was not contagious until sometime on Sunday (regardless of whether the game day test was true or false negative).

To make the situation of the Trojans even more fraught, they were victims of a false negative antigen test and several false positives during the week, according to a conference source.

Whether that player subsequently infected others is not clear at this point.

The antigen tests are known to generate false positives, and the Pac-12 has taken that possibility into account with the requirement that teams run confirmatory PCRs in those cases.

But false negatives?

That’s like trying to counter an eight-man blitz with five blockers: someone will get through – it’s just a matter of how much damage is done.

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