A month into social distancing, and with at least three more weeks to go, people hunkered down across Washington to slow the spread of the novel coronavirus are surely wondering: When is this going to end? And what comes next?
Health officials and epidemiologists are asking themselves the same questions.
“That’s what a lot of us are working on now: What’s the end game?” said Dr Elizabeth Halloran, an infectious-disease specialist and modeler at Fred Hutchinson Cancer Research Center who advises the federal government on outbreaks. “What can we do short of keeping everything shut down for 18 months or longer until we have a vaccine?”
With hundreds of new cases still being reported statewide every day, the virus hasn't vanished – and it never will. Though an influential University of Washington model suggests deaths and hospitalisations may have peaked in the state, lifting restrictions too soon could cause cases to rebound to even higher levels than before, health officials warn.
But lockdowns can't go on indefinitely, either. US President Donald Trump, who extended federal social distancing guidelines through April, is now pushing to restart businesses by early May or even sooner.
Keeping the virus under control in the long term will require an ambitious strategy that one Seattle scientist calls “the Apollo programme of our times”.
The basic approach is no different than for any other epidemic: Identify those who become infected, as well as those who have been exposed, and isolate them. But that would mean a massive scale-up of testing and contact tracing, at a time when even nursing homes still can't get enough test kits and public health agencies are swamped.
Trevor Bedford, the Fred Hutch computational biologist who made the moonshot analogy, says what's needed is new technology, including simple home tests and the use of cellphone location data to alert people who may have been exposed. Some epidemiologists say it could even be necessary to impose intermittent lockdowns through the end of the year, to keep hospitals from being flooded with patients.
If the strategies work, they will buy time for the development of lifesaving treatments and a vaccine.
“People really do need to understand the sad truth here, related to the fact that we're not going to be able to stop this outbreak,” said Dr Jeff Duchin, health officer for Public Health – Seattle & King County. “We’re trying to manage it, but people will continue to get sick. People will continue to get critically ill. People will continue to die.”
Slowing the spread, but not stopping
Staying home to reduce the spread of the virus is a stopgap measure, aimed primarily at preventing hospitals from being overloaded so those who need lifesaving care can get it. And it seems to be working. Hospitalisations are not soaring in most places, and the trajectory of new cases is beginning to flatten out, at least in King County.
Even if the same number of people eventually become infected, social distancing will greatly reduce the death toll by spreading the cases out over a longer period of time and preserving hospital capacity, Duchin said.
Slowing the spread of the virus, however, also means that most people remain susceptible. Kathryn Peebles, an epidemiologist and disease modeler at the University of Washington, estimates social distancing prevented nearly 30,000 infections and 140 deaths in King and Snohomish counties through April 8. But her modeling also suggests only about 2% of people in the two-county area have been infected, and that infections are likely to surge when restrictions end.
“I fear we’re just at the beginning of this epidemic,” Peebles said.
It’s possible the virus will fade with warm weather, like influenza. But a prestigious scientific panel advised against counting on that after reviewing the evidence at the request of the White House last week.
“Given that countries currently in ‘summer’ climates, such as Australia and Iran, are experiencing rapid virus spread, a decrease in cases with increases in humidity and temperature elsewhere should not be assumed,” they wrote.
With Washington’s “stay home, stay safe” order in effect until May 4, Duchin said he and his team will work with state and elected officials over the next few weeks to figure when – and how – to begin easing out of the lockdown.
The first condition for any changes will be a steep drop in the number of new infections, he said. Hospitals must also have reliable supplies of protective equipment and the capacity to handle the expected influx of patients.
“We want to get back to our normal lives as quickly as possible,” Duchin said, “but we have to do this in a very measured way, without overwhelming our health care system.”
Options for tracking, testing for exposure
Identifying and isolating newly infected people will be critical, so testing capacity needs to be vastly expanded, along with a system to notify people who have crossed paths with them. Those are the classic tools of the epidemiological trade, but the system quickly collapsed under the onslaught of coronavirus cases. Lack of testing left officials blind to the true extent of the outbreak, and they still don't have a good handle on it.
Public Health – Seattle & King County's exhausted staff was forced to abandon all contact tracing, the laborious work of phoning everyone exposed to an infected person and advising them to self-quarantine. Now, it's hard to envision scaling up for the massive job ahead, said Duchin, who estimated he would need at last 10 times more people.
Dr Robert Redfield, director of the Centers for Disease Control and Prevention, told NPR on Friday that the federal government hopes to deploy an army of workers to help with what he described as an aggressive “block and tackle” strategy.
The growing realization that infected people with no symptoms can spread the disease makes it even harder to know who should be tested, and means many people may have to be tested multiple times.
The high-tech alternative Bedford and others are advocating would streamline the process and move it online.
“I hope we can solve this thing by doing the traditional shoe-leather epidemiology of case finding and isolation, but at scale, using modern technology,” he wrote in a series of tweets.
Dozen of new, quicker tests are already under development or coming onto the market. The best approach would involve testing at home, Bedford said. The Bill & Melinda Gates Foundation is seeking federal approval for home delivery of nasal swabs that would be sent back to a central lab for processing.
The next step would be the use of digital tracking, via cellphone data, to almost instantaneously alert people who were exposed to someone newly diagnosed as positive. Digital tracking was a powerful tool in controlling the spread of Covid-19, the disease caused by the new coronavirus, in China, South Korea and other Asian nations – but at a cost to privacy many Americans would never tolerate.
In South Korea, where 5% of the population was tested, cellphone alerts about potential exposures were often uncomfortably detailed, including age and gender of the infected person. In Taiwan, anyone who tested positive was required to download a phone app monitored by health officials to ensure compliance with quarantine – and the country never had to close businesses or order people to stay home, said Chunhuei Chi, director of the Center for Global Health at Oregon State University.
“That detailed tracking of every single case is the reason people in Taiwan feel safe to go to bars or restaurants,” Chi said.
Bedford and others recently launched and are seeking funding for a project called NextTrace that would allow people who opt in with their cellphone data to anonymously register if they test positive. Alerts would go out automatically to others in the network who might have come close enough for exposure. Several similar programs have been launched across the country, and on Friday, tech heavyweights Apple and Google said they are introducing new tools for contact tracing based on Bluetooth technology and phone apps. How well the programs work will depend on how many people enroll.
Blood tests that detect antibodies to the virus will be another important component of the long-term control effort, Halloran said. Several versions, including finger-prick tests, are in the works, but only one has been approved by the FDA for emergency use.
People who recover from the virus will almost certainly have some level of immunity, though it's not clear how long it will last or whether it will completely protect them from re-infection, she said. Officials in Italy plan wide scale antibody tests, initially to identify health workers who might be immune, and possibly to give other workers a clean bill of health to return to their jobs.
“There are probably thousands of people in Washington and the Seattle area who had the infection but don't know it,” Halloran said. “If people want to go back to work and it turns out they were already infected, they're in a much better position.”
Rolling closures until herd immunity
Duchin, who faces the task of developing a plan that’s realistic and scalable, says he's open to innovation, but not sure all the ideas being floated will prove practical.
“My feeling about a lot of these plans is that they are to some degree aspirational and to some degree delusional in terms of the amount of resources they would require and the complexity of the burden they're placing on the public health system,” he said.
He does see the logic a Harvard team's suggestion of lifting restrictions until the number of new infections or hospitalisations reaches some threshold, then imposing them again until the numbers drop.
That's one of the scenarios Peebles and her colleagues are modeling, using 50% of ICU capacity as the trigger. Under a scenario where people are 90% compliant with the restrictions, they estimate it would require an additional 96 days of social distancing beyond May 4, spread out through the end of the year.
It's too soon to know if those types of rolling closures would be practical, or acceptable to local communities, Duchin said.
Ultimately, the only way to defang the virus is through what's called herd immunity. That means a majority of the population becomes immune, either through vaccination or surviving infection. Some have suggested it might be quicker and easier to simply protect the most vulnerable, but otherwise let the virus have its way, leaving only the hardy survivors standing. But after considering the staggering toll, governments have rejected that path.
The race is on to develop a vaccine, but even the most optimistic timelines extend beyond a year and would represent record speed for solving such a complex biological problem. In the interim, people in Washington and the rest of the country will probably have to keep adjusting their daily lives to protect themselves and keep others safe.
At some point, Duchin said, the trade-offs between the health impact of the virus and the health and socioeconomic impacts of continued shutdowns could tilt in the other direction, requiring another set of hard decisions.
"We're nowhere near that right now," he said, "but we have to be sensitive to the harms created by some of these policies." – The Seattle Times/Tribune News Service
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