It's still the early days of the coronavirus pandemic, but history, biology and the knowledge gained from our first nine months with COVID-19 point to how the pandemic might end.
The big picture: Pandemics don't last forever. But when they end, it usually isn't because a virus disappears or is eliminated. Instead, they can settle into a population, becoming a constant background presence that occasionally flares up in local outbreaks.
Many emerging viruses become part of the viral ecology. The four coronaviruses that cause the common cold are endemic, circulating in the population, and the influenza strains that cause seasonal flu predictably surge each year.
The SARS outbreak in 2003 didn't go the same way due to biology and behavior: It was much less transmissible than the virus that causes COVID-19, countries contained it quickly, and it has pretty much disappeared.
One virus, smallpox, was eradicated through widespread vaccination, and polio may be close, after decades of effort and billions in funding.
What's happening: The pandemic is deepening in the U.S., Europe and elsewhere in the world.
Experts — from the U.K.'s chief scientific adviser to pharmaceutical CEOs to the WHO — increasingly say SARS-CoV-2 is likely to circulate in the population on a permanent basis, mainly due to the foothold the virus has already established.
But what damage endemic COVID-19 causes will depend on different factors, including how often people are reinfected, vaccine effectiveness and adoption, and if the virus mutates in any significant way.
"If the vaccine is really effective, like the measles vaccine or the yellow fever vaccine, it's just going to land like a ton of bricks and suffocate this. Maybe not quite eradicate it — yellow fever and measles are not eradicated — but it'll be an utter game changer," UC Irvine epidemiologist Andrew Noymer says.
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