We were warned that this could happen.
While millions stayed home last spring, looking for summer to rest from the virus, experts worried an even bigger fall was just around the corner.
We round that corner. As cases and hospitalizations reach record levels across Europe and the United States, leaders are forced to make tough decisions about what to close and when. In the United States, President-elect Joe Biden has made it clear that he will not call for a national blockade, but more state- or local-level closures are on the table. And, in fact, many regions are already implementing more specific approaches, focusing on crowded spaces such as restaurants, bars or schools.
European countries began implementing new restrictions in October and in the United States many governors and city officials are beginning to partially curb. New York City public schools closed Nov. 19; Minnesota has bars and restaurants covered for a month starting Nov. 20; California officials enacted curfews between 10 p.m. and at 5 a.m. in certain counties until December 21st.
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It remains to be seen whether these tight restrictions will work. But scientists have studied what worked and what didn’t in the early months of the pandemic, revealing some promising approaches. New research suggests that focusing on closing or reducing capacity at transmission hotspots while keeping open parts of the economy less risky can curb exponential increases in some cases, minimizing damage to the economy.
“We don’t need to shelter completely in place to slow down transmission,” says Lauren Ancel Meyers, a mathematical biologist at the University of Texas at Austin. But these sharper approaches only work if governments set clear guidelines and people follow them, she says. Even the smartest interventions will be overwhelmed if they are enacted too late amid unbridled transmission within a community.
Here’s a closer look at what can work and what can’t.
Don’t do: what didn’t work
In retrospect, some of the measures taken in the early days of the pandemic did little to stifle it. Temperature checks and deep cleaning of public surfaces emerged as two largely ineffective measures in a global analysis published Nov. 16 in Nature Human Behavior.
At first, “no one had any idea how to stop the spread of the virus,” says Peter Klimek, a data scientist at Vienna Medical University in Austria. Instead, countries have launched the kitchen sink against the virus, taking many measures simultaneously.
Klimek and colleagues used statistical techniques to try to unravel which measures worked and which didn’t. In 56 different countries, including the United States, they assessed how more than 6,000 different interventions affected infection rates in the weeks following enactment. What they found matches what we have learned since then about the virus and how it spreads.
Temperature checks, at the border crossing or at airports, are not particularly effective because people tend to become infected long before the onset of symptoms (SN: 15/04/20). Deep cleaning of public places like subway cars seemed prudent from the start, but evidence suggests that touching shared surfaces is not a big driver of broadcast events, Klimek says. In contrast, the coronavirus spreads more easily through the air (SN: 7/7/20)
Do: transmission hotspot destination
Given the ease of aerial propagation, interventions aimed at transmission hotspots (crowded indoor spaces) worked best, especially canceling small meetings of up to 50 people. “Basically this includes closing bars, restaurants, cafes, having people work from home if possible and bans on family celebrations like weddings, funerals,” Klimek says.
Boundaries at large meetings, stay-at-home orders, and travel restrictions have also been effective, along with increased access to personal protective equipment and public education on risk management.
These investigations found that these measures were most effective when enacted earlier. For example, responding to an increase in cases quickly canceling small meetings and restricting some travel, but keeping schools open, slowed the spread as much as if all three measures were taken two weeks later, when cases were much larger, Klimek says.
“Countries facing difficult situations are likely to wait too long,” Klimek says. "It's better to act sooner and act more decisively."
Part of the hesitation to act early stems from fear of the economic consequences of the strikes. But scientists are trying to chart paths that minimize those economic costs while controlling the virus.
“If we can identify economic sectors that contribute most to transmission and less to gross domestic product, then our top candidates close,” says Katharina Hauck, a health economist at Imperial College London. "It gets the biggest impact on transmission and the least damage to GDP."
To identify those sectors, Hauck and colleagues simulated the effects of more specific constraints on the spread of disease and the economy in the UK, using both economics and epidemiology. Using detailed survey data on people’s contact levels and therefore their transmission, in different types of businesses and residences, the researchers projected the effects of restricting different sectors.
A widespread closure that only maintains essential services in 63 economic sectors, but which opens schools and universities, would keep COVID-19 hospitalizations within their capacity, according to the report released on November 16th. about $ 306 billion) in GDP lost in the next six months, compared to hypothetically leaving the economy open but allowing hospitals to be overwhelmed.
A fully open scenario would send 68,000 people to the hospital at the height of the increase, compared to the peak in the UK of around 18,000 COVID-19 patients hospitalized in April, the researchers say. But letting the virus burn in a population without sticks can have unforeseen and drastic economic consequences, in addition to causing many more deaths.
Alternatively, more specific restrictions focused on high-contact sectors such as restaurants, retail stores and entertainment venues could keep hospitals functional and allow schools and universities to remain open for the most part, along with production, construction, service centers. financial and agriculture. This scenario cost the UK just £ 26 billion (about $ 35 billion) in lost GDP, compared to keeping everything open.
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“Our study shows how we can fine-tune the closure of the economy and save both lives and livelihoods,” Hauck says. England and much of Europe are in the midst of a tighter focus this fall, with restaurants and cafes closed in many countries, but schools remain open. There are preliminary indications that these measures are changing current. Daily case counts in France, for example, fell nearly 70 percent, from a weekly average of more than 54,868 on Nov. 8 to 16,722 on Nov. 25.
Do: Reduce congestion
Could similarly targeted restrictions work in the United States?
According to an analysis published Nov. 10 in Nature, enough to limit capacity at key transmission points, such as restaurants, may be enough to reduce the exponential spread in some cities. “Closing the economy doesn’t have to be all or nothing, it doesn’t have to be a total block and a total reopening,” says Jure Leskovec, a computer scientist at Stanford University.
Leskovec and colleagues used mobile phone mobility data from approximately 98 million Americans in 10 major metropolitan areas, including Chicago, New York, Atlanta, and Washington DC This database allowed researchers to "visualize" these people as particles. , whose status is up to date. every hour as they move from their homes to places like restaurants, supermarkets and gyms. Researchers excluded schools and workplaces from their analyzes.
From this starting point, they constructed a statistical model, adjusting variables that control how easily a virus can jump from particle to particle (indeed, person to person) in different situations until the model closely matched the actual number of cases in these 10 cities. From March to May, although these cities adopted measures of social distancing.
“From an epidemiological point of view, the model is quite simple, but it shows the power of mobility in the spread of the virus,” says Leskovec. That simplicity also allowed researchers to simulate different reopening strategies, seeing how restricting mobility in different places influenced the spread of the disease.
In general, most of the predicted infections occurred in a small number of places. In Chicago, for example, their tests found that 85 percent of infections occurred in only 10 percent of places outside the home, including restaurants and fitness centers. But 80 percent of those infections could be avoided by limiting maximum occupancy at any given time to 20 percent of normal. Leskovec says these companies still retain 60 percent of the total visitors, according to his estimate, but visits have been more spread out so fewer people have gathered at any given time. “For the price of 40 percent of visitors, we are preventing 80 percent of infections,” he says.
Researchers have found that limiting occupancy is especially important in lower-income neighborhoods. Residents of these neighborhoods distance themselves less socially due to work-related demands (SN: 11/11/20), and Leskovec’s analysis predicted higher infection rates at specific points. “A single trip to the supermarket is twice as dangerous for a low-income person as a high-income person” in eight of the 10 subway areas, Leskovec says. “Low-income families go to stores that are denser than richer families and stay longer,” Leskovec says.
Limiting capacity in these often crowded places or creating other ways to distribute food in these neighborhoods may begin to improve the strong racial and ethnic health disparities of COVID-19 (SN: 4/10/20).
Stephanie Keith / Getty Images
Do: act early
While targeted closures may work, these more accurate tools are only effective if enacted before community outreach takes off. “You have to tap the brakes at the first sign that things are taking an alarming turn,” says Meyers, the mathematical biologist. “If intensive care units are starting to reach capacity, then it’s time to put the brakes on them,” with longer, more restrictive measures.
In the United States, many regions may have already passed the ideal time to start tapping the brakes with less restrictive measures, Meyers says. "Key pressure points to reduce transmission, such as restrictions on indoor dining, are also some of the hardest things to adopt." But for every day that social distancing measures are delayed, cities need on average two and a half more days of restrictions to contain an outbreak, Meyers and colleagues reported in Emerging Infectious Diseases in September.
“Waiting a week to act not only means things are likely to look worse in terms of hospitalizations, but it can also mean we have to close two and a half more weeks,” Meyers says. "So even though we're trying to avoid that kind of economic cost up front, it can bite us back."
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