Thread by @alexandraphelan

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: apps.who.int/iris/bitstream…

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:
virologydownunder.com/past-time-to-t…