More than 130 years ago, a brutal respiratory virus swept across the globe, killing a million people — out of worldwide population of 1.5 billion — before fading away, eventually overshadowed in history by the deadlier 1918 influenza pandemic.
That 1890 pandemic, which some scientists believe was caused by a coronavirus, may offer a glimpse of the modern world’s escape from COVID-19 — or at least one possible path in a future that’s still largely clouded by uncertainty.
The United States is in a desperate race to speed up vaccinations and develop herd immunity that would end the pandemic. But with several variants of the virus now emerging, including one or more that could make the vaccines less effective, it’s increasingly unclear what the finish line even looks like.
One possibility would be an echo of the 1890 pandemic: The virus slowly drops off as countries develop herd immunity due to a large majority of the population being infected or getting vaccinated. After anywhere from a few years to a few decades, it only circulates among children and rarely causes anything more serious than the sniffles.
Or the virus could be stamped out completely, or close to it, with vaccines. It could disappear like smallpox, or be pushed to such low levels in the U.S. that it shows up only in isolated clusters, as with measles.
Or it could turn into something like influenza, with the world in a constant battle to adjust vaccines to changing variants and keep the virus under control. The stakes, however, will be much higher if the coronavirus remains as deadly as it is — far deadlier than the flu — or mutates to become worse.
“We’ve had a cold reality moment” in the pandemic with the arrival of several new variants, including one in the Bay Area, in recent months, said Fyodor Urnov, director for technology and translation at UC Berkeley’s Innovative Genomics Institute. Scientists had believed that this coronavirus wasn’t as changeable as other viruses, but that belief was upended as the virus mutated quickly — setting up a race to stomp it out before more undesirable mutations arise.
“This virus is a formidable enemy,” Urnov said.
The vaccines are well tuned to the coronavirus that currently is dominant around the world — itself a variant of the original virus first identified in Wuhan, China, one year ago. The vaccines most likely will work against four new variants that have appeared suddenly in the past two months, including one that seems to have settled in the Bay Area and other parts of California.
But studies suggest that at least one of those variants, found in South Africa, may be able to partially evade the vaccine. The Bay Area variant has a particular mutation that concerns scientists, who are conducting tests now to determine if it’s resistant to some antibodies meant to fight the virus, though at this time they believe the vaccine will be effective.
And scientists worry that as the coronavirus continues to spread widely around the world more variants will emerge, potentially with mutations that could undermine efforts to control it.
“In a race between a pathogen and a host, the pathogen is going to mutate to try to adapt and be a better pathogen. As the host develops a better immune response, the pathogen develops ways of evading the immune response. And it goes on forever that way,” said Dr. Joel Ernst, an infectious disease expert at UCSF.
“I think we’re going to be in pretty good shape in the near term,” he said. “But I don’t think we know yet what the ultimate potential of this virus is.”
Short-term outlook
Many scientists like Ernst believe the new variants, even those that appear to be more infectious, won’t have a dramatic impact on the current pandemic. They also think the vaccines will remain effective enough to reach at least a temporary herd immunity.
But the Centers for Disease Control and Prevention has warned that a particular variant first identified in the United Kingdom — and which has now been found in at least 22 states — could dominate in the United States by March. That variant is roughly 50% more infectious than the currently dominant virus and would undoubtedly fuel more cases and a surge in hospitalizations and deaths, the CDC warned.
Preliminary findings reported on Friday also suggest the variant may be deadlier than other versions, but more research needs to be done.
Only 72 cases of the U.K. variant have been identified in California, but it’s assumed to be more widespread. And now another variant has been identified that may also cause faster spread of disease. That one appears to have gained significant traction in parts of the Bay Area and Los Angeles County in just the past month.
Either or both of those variants could prompt delays in lifting current stay-at-home orders or reopening schools, infectious disease experts have warned. Or they could lead to a new wave of infections in the spring that might once again overwhelm hospitals in much of the state.
The U.K. variant is more infectious in children as well as adults, studies have found, though kids are still less likely overall to be infected or have serious illness. None of the approved vaccines have been tested in children yet.
The variants also could have no effect on the short-term course of the pandemic, as long as they respond well to vaccines and the state picks up its immunization efforts. Scientists are still trying to understand how the variants behave in their human hosts.
“There’s no reason to panic,” said Dr. Grant Colfax, director of the San Francisco Department of Public Health, at a news briefing last week. “This is going to be part of this pandemic, as we see variants emerge. We’re just going to have to learn more about them.”
But a prolonged pandemic would further impact livelihoods of millions of Californians.
“The troubling thing is, we’ve never encountered something like this in our lifetimes, so we don’t have a playbook on how to navigate this,” Voss said. “It’s difficult trying to figure out how to plan for the future.”
Just a common cold
Most public health and infectious disease experts believe that with a strong national immunization campaign and a few more months of aggressive social distancing and other protective measures, the United States will come out from under this darkest period of the pandemic.
But the outlook beyond that is murky.
A study out of Emory University published earlier this month suggested an outcome similar to what some experts believe happened after the 1890 pandemic. A new virus crashed over the world, causing widespread illness and death among populations that had no natural immunity to it. Then, after many years or possibly decades, the virus either mutated to become less severe or the world built up enough immunity that it’s now toothless.
That coronavirus is now one of four that causes the common cold. Most children are infected with it by the time they’re 5, and it’s as inconsequential in adults as it is in kids.
“This could imply that our normal, tame coronaviruses that we see today have arisen in the same fashion as the virus we’re seeing now,” said Dr. Yvonne Maldonao, an infectious disease expert at Stanford. “And over time this virus will mutate into a more benign form. And with our ability to build up immunity, we’ll be progressively getting less and less sick from it.”
This theory is based on a few premises: That the current coronavirus almost never causes serious illness in young children, and that everyone else in the population will eventually develop some degree of immunity, so even if they’re re-infected they don’t get very sick. Also, it assumes that the virus will mutate to cause less serious disease over time, which is often the case with new pathogens as they adapt to their hosts and become less hostile.
“It may not disappear, it may stay, but if it stays it may become a normal, regular cold virus,” Maldonado said.
Best-case scenario
It may be possible to eradicate this coronavirus. But that will require a combination of luck and a successful global vaccination effort.
If the vaccines remain as effective as they proved in clinical trials, if the immunity they produce is long-lasting, and if the world gets to herd immunity in all corners, then COVID-19 could disappear entirely, or close to it. But it would take years, and potentially decades, to get to that point.
“We may not be able to eradicate it like we did with smallpox. But we can at least get it to a level, once we get a sufficient number of people vaccinated, where the virus will have no toehold,” said Dr. Catherine Blish, a Stanford infectious disease expert. “Hopefully we just vaccinate everyone and get rid of it altogether. But we will be dealing with this for a while.”
Global immunization would be a necessary but monumental task. The vaccines would have to reach countries devastated by war and poverty, along with the pockets of vaccine-resistant communities in the United States. Any gaps in immunity would be opportunities for the virus to spread and mutate, and potentially turn out vaccine-resistant variants.
“This is a global problem,” said Dr. Warner Greene, an infectious disease expert with the Gladstone Institutes in San Francisco. “It’s a pandemic, and we’re only as strong as our weakest link. We’re only as strong as our smallest herd.”
Constant evolution
Perhaps the most likely, and least satisfying, end to the pandemic is not much of an end at all: The coronavirus keeps spinning out variants and scientists keep refining the vaccines, and the world learns to live with COVID-19.
This might be the outcome if the vaccines don’t provide so-called sterilizing immunity — meaning everyone is protected from the coronavirus for the rest of their lives. Depending on how long immunity lasts people may need regular boosters as often as every year.
There are reasons to be hopeful, though. Even if vaccine immunity isn’t permanent, it may provide long-lasting protection that prevents serious illness or death, so another mass immunization effort may not be necessary.
Plus, the vaccines that have been developed so far can be easily changed to keep pace with variants, infectious disease experts say. If a new variant emerges that is able to elude vaccines, developers can tweak the recipe and probably have it ready to inject into arms within a few months.
But that would require constant vigilance to quickly identify new variants and a strong system for vaccine distribution. The coronavirus would remain a threat for decades to come.
“These variants could make us very busy and could prevent a full success of the vaccine,” said Dr. Melanie Ott, director of the Gladstone Institute of Virology. “Yes we can adapt the vaccine. But we know the influenza vaccine is not 100% effective, and every year we have to guess what will be the predominant strain and build the vaccine. We really want to avoid that. But we might end up in a situation that is similar to what we have with influenza.”
The United States will get some measure of control over the coronavirus eventually, infectious disease experts said. Between vaccination efforts and the natural immunity people will have from being infected, the country will almost certainly reach herd immunity, and that will make a profound dent in the spread of disease here.
How long that takes is unclear, and depends as much on people’s behaviors as on the virus itself. New variants that aren’t quite as responsive to vaccines may mean more people need to be vaccinated to reach herd immunity. Addressing vaccine hesitancy could add months to the timeline. But if everything goes smoothly, some communities may get to herd immunity by the end of summer.
Even if the virus can’t be totally quashed, it can be contained, experts said. “I’m mildly but not exceptionally concerned about the future” of this pandemic, said Blish. “The good news is we’ve learned a lot from this and we’ll be able to respond even better and faster next time.”
When COVID-25 comes along, the world will be more ready.
San Francisco Chronicle staff writer Michael Williams contributed to this story.
Erin Allday is a San Francisco Chronicle staff writer. Email: eallday@sfchronicle.com Twitter: @erinallday
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