Thread by @bopinion

World leaders are beginning to loosen Covid-19 restrictions well before an effective vaccine or treatment for the disease is available.

This means secondary outbreaks are a near certainty trib.al/pL8CEW4

What’s uncertain is how devastating future surges of infection will be.

If they’re sporadic, death rates will stay low, and life may inch back toward normalcy. If they’re large, some regions may dive back into shutdown mode, extending the economic damage trib.al/pL8CEW4

Countries are not entirely powerless over their fates. Areas with widespread testing and contact-tracing will most easily be able to detect outbreaks.

But nature will play a significant role, too, and an unpredictable one — starting with the weather trib.al/pL8CEW4

While there’s some evidence that Covid-19 doesn’t care for heat, most transmission has been occurring indoors.

🇹🇭🇸🇬Outbreaks in warmer nations like Thailand and Singapore suggest that dramatic summer suppression is unlikely trib.al/pL8CEW4

Nevertheless, outbreaks in the Northern Hemisphere this summer could be smaller, and that would buy valuable time to make progress on:

🧪Testing
💉Developing treatments
🚑Reinforcing health systems trib.al/pL8CEW4

Theoretically, the coronavirus might peter out, as viruses do, if populations acquire immunity.

While most countries have embraced social distancing, Sweden has imposed only mild restrictions to reduce the economic impact of the pandemic trib.al/pL8CEW4

Racing toward “herd immunity” isn't an explicit aim of the policy, but it’s a threshold that Sweden's chief epidemiologist thinks could be achieved in Stockholm within weeks.

The problem is that scientists know little about acquired immunity to Covid-19 trib.al/pL8CEW4

🇸🇪Thus, Sweden is taking its chances.

If immunity is easily gained and long-lasting, infection rates should decline. But if it’s unreliable, the world could face annual or biennial outbreaks for years to come trib.al/pL8CEW4

When cold weather returns in the fall, countries may face a new challenge: the simultaneous return of Covid-19 and the flu.

It will help if more of the world’s population gets a flu shot. In an average year, however, less than half of American adults do trib.al/pL8CEW4

🦠Scientific breakthroughs could also steer the trajectory of Covid-19: The discovery of an effective treatment would greatly reduce suffering and strain on health care systems.

By the fall, data on lab-grown antibodies might be available trib.al/pL8CEW4

Treatments and vaccines now in the works are aimed at the version of Covid-19 that is currently spreading. A mutation could undermine progress.

In the face of so many unknowns, countries have no choice but to approach reopening with extreme caution trib.al/pL8CEW4