Three potential futures for Covid-19: recurring small outbreaks, a monster wave, or a persistent crisis

via statnews

As epidemiologists attempt to scope out what Covid-19 has in store for the U.S. this summer and beyond, they see several potential futures, differing by how often and how severely the no-longer-new coronavirus continues to wallop humankind. But while these scenarios diverge on key details — how much transmission will decrease over the summer, for instance, and how many people have already been infected (and possibly acquired immunity) — they almost unanimously foresee a world that, even when the current outbreak temporarily abates, looks and feels nothing like the world of just three months ago.

It is a world where, even in Western countries, wearing a face mask is no more unusual than carrying a cellphone. A world where even at small social gatherings a friend’s occasional cough feels threatening, where workplaces have the feel of hot zones, and where taking public transit is not as much environmentally correct as personally dangerous.

“October 2020,” said emerging diseases expert Amesh Adalja of the Johns Hopkins University Center for Health Security, “won’t look nothing like October 2019.”

And neither will October 2021, according to an analysis released on Thursday by epidemiologist Michael Osterholm of the University of Minnesota and his colleagues. They envision three possible futures, depicted as seascapes, their waves of different heights and widths approaching the unseen and unsuspecting beachcombers on a placid shore.

In one future, a monster wave hit in early 2020 (the current outbreak of millions of cases and a projectedhundreds of thousands of deaths globally by August 1). It is followed by alternating mini-waves of much smaller outbreaks every few months with only a few (but never zero) cases in between.

In the second scenario, the current monster wave is followed later this year by one twice as fierce and even longer-lasting, as the outbreak rebounds after a summer when a significant drop in the number of cases and deaths led officials and individuals to let down their guard, relax physical distancing more than was safe, and fail to heed (or even detect) the early warning signs that a new outbreak was gathering force. After this doubly disastrous second wave, the sea is almost calm, marred only by an occasional wave of cases that number barely one-fifth of what the fall and spring of 2020 saw.

In the third possible future, the current wave creates a new normal, with Covid-19 outbreaks of nearly equal size and, in most cases, duration through the end of 2022. At that point, the best-case scenario is that an effective vaccine has arrived; if not, then the world experiences Covid-19 until at least half of the population has been infected, with or without becoming ill.

What all three scenarios agree on is this: There is virtually no chance Covid-19 will end when the world bids good riddance to a calamitous 2020. The reason is the same as why the disease has taken such a toll its first time through: No one had immunity to the new coronavirus.

“This pandemic is not going to settle down until there is sufficient population immunity,” slightly above 50%, epidemiologist Gabriel Leung of the University of Hong Kong told a New York Academy of Sciences briefing.

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Since the world “is far from that level of immunity,” said Osterholm (he estimates that no more than 5% of the world population is immune to the new coronavirus as a result of surviving their infection), “this virus is going to keep finding people. It’s going to keep spreading through the population.” And that, he said, “means we’re in for a long haul.”

The uncertainty over what the long haul will look like — a staggering third scenario or a much less brutal first — reflects the host of unknowns surrounding an outbreak unparalleled in modern history. Scientists are still racing to understand everything from the basic biology of the virus (how much do warm temperatures and high humidity reduce transmission? how many people were infected, and if they have immunity, how long does it last?) to the impact of mitigation strategies (does closing K-12 schools help enough to justify the cost to children’s education?). The answers will affect which future comes to pass.