The Epicenter of a Growler Outbreak

Cherise Rohr-Allegrini, PhD, MPH
4 min readMay 13, 2020

This city, San Antonio, is built on community. So like many communities across the world, the physical distancing thing has been, well, difficult.

This neighborhood, Southtown, loves its local ice houses and breweries. So when they all had to close down on March 18, the community found a way to keep business alive and spread community love.

The Index Case (IC) visited The Friendly Spot Ice House and purchased a growler of beer. Said Growler, hereby known as G0, was delivered to a neighbor, The Clings, to start the #CommunitySpread.

Drinking beer with friends COVID style “The Friendly-Chain-Growler!!” Here are the rules:

Clean growler bottle with a wipe, just to be extra cautious. Wash hands.

  1. Open Beer
  2. Drink Beer
  3. Attempt to sign the growler with some sort of paint pen.
  4. Go to The Friendly Spot and refill the growler (They are open Friday & Saturday 4-9p; You also must order food, Texas Law)
  5. Place the growler on a friend’s porch
  6. Post this on their Facebook Page.
  7. If the growler is not passed on within 2 weeks, a series of Biblical Plagues will start visiting your home. All things considered, you don’t need that kind of extra trouble.
  8. Bonus Viral Karma points if you buy an additional growler and start a new strain #CommunityGrowlerSpread

The growler will be named after the first person to receive it.

So now folks are asking about the R0. Our resident expert described it thus:

“You will find that some growler strains lose potency (or are completely ineffective, as in the ill-fated Sandiman) while others gain in strength like the Mores or the Clings… either because the proximity/contact rate or, perhaps, because of potency of growler contents.

Since components of Ro = period of lowered inhibitions that leads you to pass on growler and/or buy another to pass on (Infectious period) * number of growlers passed per individual (contact rate = 1 unless you get a second growler) * number of growler passing events per contact (efficacy of transmission- which appears to be quite high except in the case of thievery), we should be able to calculate in this case.”

While Southtown, where #CommunitySpreadGrowler started, is the epicenter (and really, Southtown is ALWAYS the Epicenter of Fun), “The Friendly-Chain-Growler!!” has spread into other parts of San Antonio. For now, it appears to be contained to the inner-loop/urban core, but not for long. (Local epidemiologists are still working on a map.) Rumor has it that a cluster in the outer loop is itching to get infected.

There’s some crazy stuff going on in this D-Street Cluster that might throw off our R0 calculations.

Despite two super spreaders (Index Case and The Alle), the R0 appears to be about 2 (maybe 3 given that D-St cluster). Like most epidemiological data in an outbreak, some data are missing:

*G4, G6, G8, and G9 have not passed on their growler. Is this because they’re dead end hosts? Was their growler not contagious? Do they just have a longer incubation period? We do know that The Garcia is an outlier but we’ve lost contact with the others. There’s at least one hesitant to give info on their contacts. They might need some coaxing.

Ignore the nose above the mask, please.
  • Dates of exposure are unclear for about half the cases. We know from interviews that the Index Case (IC)continued to spread the Growlers over a 14-day period. The Contact Tracer neglected to write down all the details though, and IC is elusive. Rumor has it IC is still contagious and infecting more people. After a lull, The Alle also appears to still be contagious one month after first exposure. The Alle has been faithful about checking in with the epidemiologist to note days of contact.
  • No doubt some other infections will be re-activated. That’ll change our R0 over time.

A diligent epidemiologist could go back through many facebook posts to determine the dates, but said epidemiologist is already doing that for that other outbreak that is ongoing, and priorities…

  • There are also rumors that mutant strains have popped up in the form of growlers from other neighborhood breweries, like Freetail and Künstler Brewing, but local experts have been unable to detect them.

As in most outbreaks, residents are asking “Is there immunity to the #CommunitySpreadGrowler?” We won’t know for sure for many months, but our resident expert added:

Though there appears to be no natural immunity to getting infected with the growler again, there appears to be a social immunity in terms of the infected’s desire to pass on the infection to a new household.”

Even in the era of physical distancing, while we protect our friends and neighbors from this potentially deadly disease, We’re All #InThisTogether. The community spirit of Southtown is highly contagious.

(Names have been changed to protect the privacy of those infected)

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Cherise Rohr-Allegrini, PhD, MPH

Dr. Rohr-Allegrini is an epidemiologist and tropical disease scientist currently working to prevent diseases through immunizations.