It’s time for a Pandemic thread for #COVID19

(prompted by questions from the excellent @MackayIM & @onisillos - thank-you)

What is a pandemic?
Are we in a pandemic?
How do pandemic and PHEIC declarations differ?
What is the impact of declaring a pandemic?

(1/?)

2. A pandemic refers to the spread of a disease worldwide or over a significant proportion of the world, generally considered to be two or more continents. “Pandemic” is a descriptive term, not a legal term, and specifically describes spread, not severity, of a disease.

3. Spread is more than just cases in a country but transmission. But @WHO pandemic guidance no longer delineates b/w limited/sustained human to human transmission (after H1N1). Rather, WHO uses 4 phases: pandemic is simply “global spread” with severity risk assessed separately.

4. However, a big disclaimer: WHO pandemic guidance (and phases) is based on influenza. #COVID19 may warrant a different approach but the classic definition (above) would arguably still apply as a descriptive term.

Here’s the WHO Pandemic Flu guidance: https://apps.who.int/iris/bitstream/handle/10665/259893/WHO-WHE-IHM-GIP-2017.1-eng.pdf;jsessionid=FF0E44DE342CCEF9F0A31E1EFB14C8E8?sequence=1

5. Who decides if we're in a pandemic? @WHO decides if we're in a pandemic? No doubt some experts believe we've already met the pandemic definition for #COVID19. As the lead global health agency, folks likely waiting for WHO DG to make this as a statement of fact first.

6. In contrast, PHEIC is a legal declaration the DG makes under IHR: an extraordinary event posing public health risk through int'l spread & requires coordinated international response. A PHEIC doesn't require an outbreak be a pandemic (but a pandemic is likely already a PHEIC)

7a. What is the impact of a pandemic declaration?
(international law)
IHR - no additional powers in a pandemic: it’s all about that PHEIC.
For flu, relevant for distributing vaccines & antivirals under PIP Framework. But there's no PIP Framework equivalent for #COVID19.

7b. What is the impact of a pandemic declaration?
(national law - varies country to country)
regulatory and funding agencies may have laws that depend on a pandemic declaration.
Some contracts (e.g. insurance especially) may have clauses trigger on a pandemic.

8. Are we in a pandemic? I think we are incredibly close:
more than incidental local transmission in Asia (China, South Korea, Japan, Singapore, Hong Kong, Iran) & Europe (Italy).
assume some undetected spread occurring globally.

But, I think we are still on the cusp.

9. So what would I do if I were DG? Focus on a “pandemic” can be distracting.
If facts meet definition, delaying could undermine trust.
Declaring could shift global response to both containment & mitigation & must be coupled w a tool to help countries assess their own risk

10. I'd watch next 7 days v. closely for transmission in a new country or signif. in Iran, Jordan or Italy. If so, separate to "pandemic", I'd convene Emergency Committee to advise on mods to the PHEIC Temp Recs to help all countries esp. countries w weak health systems. END

[sidebar citation for classical definition].
This is from Gordis, Epidemiology (6th edition) and shows you the high-level and descriptive nature of the term "pandemic" from an epi perspective.

And also, Porter, A dictionary of epidemiology, 5th edition. (2008) defines pandemic similarly, but without specific geographic criteria: "An epidemic occurring worldwide or over a very wide area, crossing international boundaries, and usually affecting a large number of people"

For some brilliant answers on the public health communication perspective of a pandemic, this is an excellent piece: https://virologydownunder.com/past-time-to-tell-the-public-it-will-probably-go-pandemic-and-we-should-all-prepare-now/