On Sunday, after a frightening spike in the number of people infected and killed by COVID-19, the coronavirus disease that the World Health Organization on Wednesday declared a global pandemic, the Italian government enacted a mandatory lockdown in Lombardy and fourteen other northern provinces, including the cities of Milan and Venice, and the tiny nation of San Marino. In addition to a cordon sanitaire, which halted travel into or out of the affected areas, the lockdown prohibited the sixteen million people living inside the so-called zone rosse from any movement that was not required for work, health, or other “necessary” reasons. The decree also forbade Masses and funerals, closed movie theatres and museums, and required shopping malls and supermarkets to stay closed on weekends. On Monday, a day after Italian news organizations showed videos of people running to catch the last trains out of Milan, Giuseppe Conte, Italy’s Prime Minister, extended the emergency measures to the entire country.
In response to its own COVID-19 outbreak, China had already imposed strict restrictions on the movements and activities of fifty-nine million people in Wuhan and other parts of Hubei province in January, a public-health intervention at a scale that was, in the words of a W.H.O. official, “unprecedented in public health history.” But the quarantine in Italy, whose ingovernabilità is a recurring national joke and occasionally the matter of a rueful pride, was made even more shocking by how quickly it was felt to be necessary. As recently as February 20th, the country had only three confirmed cases of COVID-19. From that date until Monday, when Conte appeared on television to declare that “all of Italy is a protected zone,” was just eighteen days.
For Americans watching what was happening in Italy, it was impossible not to wonder whether, in looking across the Atlantic Ocean, we were also peering into our own near future. In the United States, as of Sunday, the number of confirmed COVID-19 cases was five hundred and thirty-nine, or about one and a half cases per million people. Italy reached that same relative level on February 23rd, which suggests that we could still have at least two weeks to slow the spread of the disease before it reaches the levels that prompted Italy’s national lockdown. (By Wednesday, the number of American cases had topped a thousand.) But that might be a best-case scenario. Virtually everyone—with the possible exception of Donald Trump—now recognizes that a persistent shortage of available tests for COVID-19 in the United States means that we are almost certainly undercounting the actual spread of the disease compared to other developed countries.
At present, COVID-19 appears to be relatively mild in eighty per cent of cases, but the reason for the stringent measures in China, Italy, and elsewhere is that some fifteen per cent of cases are severe, meaning they would likely need hospital care, and the remaining five per cent are critical, meaning that they need treatment in an intensive-care unit. (Research so far suggests that the populations at greatest risk include the elderly, the immunocompromised, and those with underlying health conditions, such as hypertension, diabetes, and lung disease.) The W.H.O. estimates that the global proportion of COVID-19 cases that prove deadly, known as the case-fatality rate, is 3.4 per cent, but epidemiologists are quick to caution that early estimates of the C.F.R. often skew high, since the most serious suspected cases are usually tested first, and mild cases sometimes go unreported altogether. What’s more, the C.F.R. is not a fixed property of the disease: it depends, in no small part, on the ability of the health-care system to provide adequate care to the sickest patients. This is why epidemiologists insist on the importance of limiting not just the absolute scale of the epidemic but also the speed of its spread. A country with ten thousand cases of COVID-19 can expect around five hundred of those patients to require intensive care. But the rate at which those critical cases appear—whether they require intensive care all at once, or show up at a pace the medical system can handle—can have a significant impact on how many sick people eventually die from the disease. The importance of slowing the rate of new cases, what public-health experts call “flattening the epidemiological curve,” is suggested by a recent W.H.O. report. During the early stages of the epidemic in Wuhan, when the hospitals were overwhelmed with new cases, the fatality rate was 5.8 per cent, as compared to 0.7 per cent elsewhere in the country.
At the community level, epidemiologists tend to speak of two different paradigms to limit both the extent and the rate of infection. The first, known as containment, is used at the start of an outbreak. It involves tracking the dissemination of a disease within a community, and then using isolation and individual quarantines to keep people who have been infected by or exposed to the disease from spreading it. According to Caitlin Rivers, an epidemiologist at Johns Hopkins, “the reason that we want to find those people early is so that we can make sure that they stay out of circulation in the community and also to make sure that they get the care that they need as soon as they need it.”
Rosalind Eggo, along with a team of researchers at the London School of Hygiene & Tropical Medicine, where she works on epidemiological modeling, created a mathematical model to predict the spread of COVID-19. She told me that to halt the spread of an outbreak that started with twenty infected people would likely require public-health authorities in a community to trace the contacts of anywhere from forty to a hundred people per week, with a better than eighty per cent success rate. Contact tracing is time-intensive work: the European Centre for Disease Prevention and Control, the European Union’s equivalent of the C.D.C., estimated that it would take about a hundred person-hours of work to trace the contacts of each confirmed case of the COVID-19. But if done quickly, and at the proper scale, the method can be effective. Containment, coupled with school closings and some other so-called social-distancing strategies, appears to have limited the spread of COVID-19 in Hong Kong and Singapore. But those countries started their efforts while the outbreak was still in its infancy. “If you act early enough, you can stay in the containment phase,” Jeremy Konyndyk, a senior policy fellow at the Center for Global Development, who helped lead the Obama Administration’s response to the Ebola outbreak in 2014, told me. “You still face the threat of reintroductions from abroad, so containment is ongoing, but it saves the most lives, preserves your health system, and ultimately, in the long run, it nets out to the lowest amount of disruption. But you have to choose that disruption early to get that outcome.”
America is a big country, and what we are seeing is not a single randomly distributed epidemic but a network of smaller, more intense outbreaks, particularly in places like Seattle, the San Francisco Bay Area, and New York’s Westchester County. In communities where a local outbreak gets out of control, Rivers says, “there comes a tipping point in epidemics where you’re finding a lot more people who are unlinked” to known cases. “That’s a sign that contact tracing is not scaling appropriately.” Though public-health authorities may continue to trace contacts after community spread has begun—in order, for instance, to better understand the particular features of how a disease spreads—epidemiologists generally recommend incorporating the mitigation paradigm. In practical terms, this means redeploying public-health workers away from contact tracing and disease surveillance and towards efforts with a broader reach, including working with schools to determine when to close and when to reopen, with businesses to protect their employees and their customers, and with hospitals to prepare for a surge of new patients. Communities typically implement so-called social-distancing measures as well, such as cancelling conferences, sporting events, and other large gatherings. This has already occurred in Seattle, where gatherings larger than two hundred and fifty people have been banned and where, starting tomorrow, the public schools will be closed for two weeks. “Mitigation starts with the idea that we will probably not drive transmission to zero,” Rivers said. “So then we start thinking about what we can do to prepare our hospitals and communities to reduce transmission.”
Such interventions can be effective in slowing the spread of the virus—along with widespread testing, they appear to have calmed the epidemic in South Korea—but, as Rivers was quick to note, they can also place disproportionate burdens on people who are economically and socially vulnerable. “When you close schools and have kids stay home, the kids who participate in free and reduced-price meal programs might not have access to food. Or their parents who now have to stay home with them might be hourly-wage workers, and so they’re missing out on their paycheck. Maybe those parents are health-care workers and so now maybe the local hospital is down personnel.”
This week in New York, it has been possible to watch the shift from the containment to mitigation measures in real time. On Sunday, Scarsdale closed its schools after a middle-school faculty member tested positive for COVID-19. Area universities—Columbia, Fordham, Hofstra, and Yeshiva among them—either cancelled classes or implemented plans to host them remotely. And on Tuesday, Governor Andrew Cuomo announced a mile-radius “containment area” was going into effect in New Rochelle, which is believed to be the center of one of the largest clusters of cases in the country. The zone was not exactly a quarantine—people would still be allowed to move freely in and out of it, and small businesses could remain open, but large gathering places, including schools and houses of worship, will be closed for at least two weeks. “We are moving from containment to mitigation,” Cuomo said, “and because much of the transmission of this disease tends to happen on a geographic basis, we are attacking this hotspot at the source.”
The Chinese and Italian experiences with COVID-19 suggest that the two major epidemiological response paradigms may soon be joined by a third: lockdown. Whether such a measure would be feasible in the United States depends on a host of unresolved medical, economic, and legal questions. Konyndyk, for his part, believes that at least one American city will likely face the sort of crippling surge in cases that caused Italy, on Wednesday, to tighten its national lockdown even further. Still, there remains an opportunity to keep things from getting so bad, at least in most parts of the U.S. At a hearing before the House Oversight Committee on Wednesday morning, Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, told members of Congress that “if we are complacent and don’t do really aggressive containment and mitigation,” the number of COVID-19 cases “could go way up and be involved in many, many millions.” But he also insisted that this was not an assured outcome. The epidemic “is going to get worse,” he said, but how much worse will depend on “our ability to do two things: to contain the influx of people who are infected coming from the outside, and the ability to contain and mitigate within our own country.”
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