David Fisman Profile picture
15 Sep, 19 tweets, 6 min read
In follow up to some of the remarks I made to @CBCIsmaila on @metromorning this am...here's a plot of test positivity in Ontario over time. This is a pretty good reflection of disease activity b/c it adjusts for different testing rates in different age groups.
@CBCIsmaila @metromorning You can see that positivity is really taking off in older kids, teens, and young adults, probably reflecting factors that @heysciencesam outlined so beautifully in her recent thread.

These younger people are overwhelmingly going to be ok, and we don't see a major surge in hospitalizations yet in Ontario. The problem is that hospitalizations are a lagging indicator, and if you're reacting to hospitalizations, you've missed the boat.
That's because of the lags baked into this system...given delay from infection to symptoms, symptoms to testing, testing to test reporting, what we see today likely reflects transmissions from 2 weeks ago.
And those infections in younger people aren't going to stay sealed off from other groups in society (don't @ me, this is my job, it doesn't work that way).

We can see that in this very nice heat map from France:
And of course that's a path that leads to this:

None of this is particularly surprising at this point (if you're surprised, you haven't been paying attention!).

The late Babak Pourbohloul used to say: "We model infectious diseases to move from data to understanding, because when we understand we can predict and control"
This is now a predictable process. That's great, because that defines how we're going to control it!

We know this comes from closed-close-crowded-continuous (4 C's) and it's gonna get worse as it gets cold (a 5th C!).
We know that by being proactive and acting in a limited way, we avoid the deaths, health system strain and economic damage that come from being reactive once our ICU's are filling up.

I've made a broad brushstrokes proposal in this regard before:

And @cdavidnaylor described this beautifully on @CBCNews last night...the urgency of actually using the tools in the toolbox, rather than wringing our hands and waiting for perfect tools.

But what can we do now, proactively, in Ontario?

Well, as someone once said: if it keeps on rainin, the levee's gonna break. We have to use the levers at our disposal to surgically but impactfully increase contact rates.

Easy wins: decrease indoor gathering sizes. 50 was never smart. 10 is great, 30 too high.

Take a really hard look at indoor restaurant service, which from multiple data sources (credit card spending, epidemiological data) is a driver of unrecognized spread.
Find ways to support restaurants: outdoor patios, takeout. Compensation if need be...cheaper than a broad lockdown.

Bars, strip clubs, casinos, museums...same.

Does this suck? Yes. Does doing it anyway in a month, when ICU are groaning, suck worse? Yes. Be a grownup.
I've always said schools are the one large gathering that's hard to close. Try to keep them open, as they're hugely beneficial for society as a whole.

But do the work, and stop gaslighting, Mr. Lecce. Spend the money to get those class sizes down. Innovate on outdoor ed.
Cohorts, modified school days, staggered entry.

There's an effing playbook on this now, ffs.

Spend the money the federal government gave you. You're risking a multibillion dollar economy because of your apparent hate-on for public education.
And please start taking the long view.

We need to aggressively start using the tools in our toolbox. If PHO lab can't/won't get up to speed, please partner with private labs that will.

Appoint a CMOH who understands this disease and can communicate.

Etc. Nothing new here...
Have the political courage to do the right thing, even though by doing the right thing nothing will happen and people will say you overreacted.

*DECREASE contact rates 😳😔

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More from @DFisman

19 Sep
New school-focussed sars-2 seroprevalence work from Switzerland:


“73% of children reported COVID-19 compatible symptoms since January 2020, but none were reported more frequently in seropositive compared to seronegative children.”

“Seroprevalence of children was very similar to seroprevalence of randomly selected adults in the same region in June-July 2020”

Yup. But we based school plans on wish-based policies, and insisted children don’t get infected. Unreal.

@DrZoeHyde @AshTuite @AmyGreerKalisz
Symptom-based screening may not be super-duper discriminative? Image
Read 4 tweets
9 Sep
Place-based nature of COVID-19 transmission might point the way forward for Ontario, on getting as close as we can to elimination. Would need ramped up testing, better resourced contact tracing, QR code readers, and genotyping of strains.
But we could imagine places/activities plotted on a 2-D plane...economic value on one axis, and vulnerability to (aerosol) transmission events (closed, close, crowded, continuous exposure).
It might look something like this:
Read 20 tweets
7 Sep
@thielen_l I think the best way to think of this is just to think about what happens if you get a cut anywhere on (or in) your body: you bleed.

Why? Because every inch of your body is full of blood vessels. Those vessels aren’t just “water mains”...they are active organs that adapt...
@thielen_l To changing environmental conditions, and physiological stresses that your body is constantly confronting. They get wider and narrower as needed, they make chemicals needed to stop leaks (clotting)...
@thielen_l they become leaky as needed in order to fight infection (the redness around a pimple!)

These functions are guided by the miraculous lining of these tiny blood vessels: that’s endothelium.
Read 7 tweets
4 Sep
I want to encourage everyone to get their flu shots. I do research on flu and have a lot of respect for the disease...it kills a few thousand Canadians every year.
But to put in perspective the challenge we face, the infection fatality ratio for COVID is around 100 x that for flu. The seasonally juiced R for COVID is likely to be higher due to greater susceptibility (will it move back to 2.5? Flu's R is usually around 1.5).
By all means, get your flu shot and your pneumococcal vaccine too if you're in a recommended age group.

But this year, these threats are on profoundly different levels. That's chilling to those of us who work in healthcare and know what a bad flu year looks like...logjam.
Read 4 tweets
28 Aug
Regarding the CMOH's assertion that healthcare workers don't get COVID-19 in healthcare, just took a peek at case data this am. This is an old set (July 26). Restrict to outbreaks, remove LTC, restrict to healthcare workers.
There are 449 unique outbreaks that involve healthcare workers and not long term care. In 260 of these, there's only a single HCW infection.

In the remaining 189 outbreaks the number of infected HCW ranges from 2 to 29. The mean is 4.4, median is 3.
19 outbreaks have involved > 10 healthcare worker infections. These have been widely distributed throughout Ontario, but 5 have been in Toronto, and 3 in Niagara and Peel. The largest outbreak was in Peel.
Read 4 tweets
27 Aug
@DrKateTO You know, if they actually wanted to understand where risk comes from, they’d need to do phylogenetics

Healthcare workers are infected at a rate 20 x that of the general population in Ontario. It’s an extraordinary reach to suggest that’s all from increased access to testing
@DrKateTO Let’s do this very simply...the assertion is that hcw being infected at a rate 20 x that of the gen pop is due to over testing and none of them get this in hospitals because [insert stuff about a a hospital in Netherlands and whatever other bullshit here]
@DrKateTO But we have seroprevalence data now. In a dataset from July 26 I have 6,300 individuals identified as healthcare workers. What’s the denominator?

According to cihi there were 155k nurses, 34k doctors, 20k dental professionals, around 20k allied health. Let’s say 250k or so
Read 9 tweets

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