Mt. Vernon Choir: NOT (Necessarily) Asymptomatic Spread

One of the most disturbing aspects of the Corona epidemic is the fact that some individuals can spread the virus despite a lack of symptoms. This is an important consideration for those hoping to avoid catching or spreading the illness, as well as for government officials considering what role they may have protecting individuals in the meantime. Viruses don't teleport, so it would clearly behoove us to understand how this occurs, how often it occurs, and how we can best reduce the chances of it occurring.

A big part of understanding the problem is reporting it correctly, neither refusing to acknowledge the problem nor blowing its severity out of proportion.

Unfortunately, a superspreading event on (or before -- See note on update at bottom.) March 10 at a church in Mt. Vernon, Washington was apparently misreported as an example of asymptomatic spread long enough ago that it seems to have become common "knowledge." This event, for which early reports put the number of infected at 45 and later ones at 52, is, unsurprisingly, frequently used to justify "lockdowns". (In addition to this being mislabeled as asymptomatic spread, many second-hand reports incorrectly credit the choir members with social distancing.)

Here's one example of this mischaracterization, which cites the earlier number and continues:

And if approximately 50% of individuals catch this virus from asymptomatic carriers, one must ask, how are these carriers spreading the virus? They are not coughing and sneezing. The answer is probably aerosolization, were the virus can float in the air and be picked up later by an unsuspecting passerby. [notes omitted]

And Here's another:

The church choir in Washington State. Even though people were aware of the virus and took steps to minimize transfer; e.g. they avoided the usual handshakes and hugs hello, people also brought their own music to avoid sharing, and socially distanced themselves during practice [sic  -- See below.]. A single asymptomatic carrier infected most of the people in attendance. The choir sang for 2 1/2 hours, inside an enclosed church which was roughly the size of a volleyball court.

Both articles reasonably postulate aerosolization as a mechanism, and to the best of my knowledge, this can occur, but is not known to be a major cause of transmission. Droplets are. And if this person had "cold-like" symptoms and spent lots of time in a crowded room, I'm not so sure we need that explanation for this event.

From the paper:

No choir member reported having had symptoms at the March 3 practice. One person at the March 10 practice had cold-like symptoms beginning March 7. This person, who had also attended the March 3 practice, had a positive laboratory result for SARS-CoV-2 by reverse transcription–polymerase chain reaction (RT-PCR) testing. [bold added]

And now, with this event having been looked into in more detail, we learn the following:

Image by Colin Michael, via Unsplash, license.

So, 61 members of the Skagit Valley Chorale, half of the choir's singers, came to the evening practice at the Mount Vernon Presbyterian Church, according to the Los Angeles Times, which broke the story.

One of those singers had COVID-19. This person had cold-like symptoms starting on March 7, but didn't realize it was the new coronavirus until a test later confirmed the diagnosis, according to the CDC report, which was written by Skagit County Public Health (SCPH) professionals. People infected with SARS-CoV-2, the virus that causes COVID-19, are most infectious from 2 days before through 7 days after symptoms begin, SCPH said in the report, "which could have placed the patient within this infectious period during the March 10 practice."

The practice lasted 2.5 hours. Several members arrived early to place the chairs -- arranged in six rows of 20 and spaced 6-10 inches ... apart. Once seated, the singers practiced together for 40 minutes, split into smaller groups for a 50-minute practice block, took a 15-minute break that included shared snacks of cookies and oranges, and reconvened for a final 45-minute singing session. [bold added]

So much for this being an example of asymptomatic spread, or at least a clear-cut one. It remains a highly relevant cautionary tale, but not so much regarding the possibility of asymptomatic spread. Misreporting it as such can fuel two different kinds of inappropriate reactions: (1) panic, by feeding fear of the unknown, and (2) dismissal of the danger of this disease, in the vein of "them so-called experts got it wrong again."

We don't need to hunker down in our homes in fear, but we should stay home or mask up at least until tested, if we feel a cold coming on. And we do need to weigh the risk of prolonged indoor group activities. Perhaps the person with the cold didn't seem sick to the others.

I bring this up, because twice in the past few days, I have heard lay people I greatly respect mention this incident as a case of asymptomatic spread. It isn't, and we should all be clear on that going forward, in the name of eventually defeating or learning how best to cope with this virus as soon as possible.

-- CAV

Updates

Today: Very shortly after posting, I realized that we're not completely off the hook of pre-symptomatic spread: There was a March 3 practice. I edited a few sentences accordingly. That said, this is not a clear-cut example of asymptomatic spread.