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Huge US study pinpoints top virus hubs: All the venues Israel plans to open next

Researchers say 8 out of 10 transmissions happen in crowded indoor spots, singling out gyms and restaurants, which are slated to open soon under Israel’s lockdown exit plan

Nathan Jeffay is The Times of Israel's health and science correspondent

A gym during the pandemic (Drazen Zigic via iStock by Getty Images)
A gym during the pandemic (Drazen Zigic via iStock by Getty Images)

A massive American study claims to have identified danger points where the coronavirus spreads most — and their key culprits are some of the very places slated for imminent reopening in Israel.

Gyms, which are widely expected to open later this month, were flagged as major transmission hubs, along with recreation venues of the sort Israel is expected to reopen on November 29: restaurants and cafes. Hotels, which are slated for a December 13 reopening, were also said to be hotspots.

The researchers also pointed to the reopening of places of worship as contributing to a rise in US cases. Israel has already allowed indoor communal prayers to restart with limited attendance, and is expected to gradually increase capacity.

After studying data that tracked the movement of some 98 million people over a two-month period, the American researchers suggest that around 80 percent of transmission happened at crowded indoor venues, especially these hubs.

“On average across metro areas, full-service restaurants, gyms, hotels, cafes, religious organizations, and limited-service restaurants produced the largest predicted increases in infections when reopened,” they wrote.

The research, just published in the peer-reviewed journal Nature, comes as some Israeli health experts are warning of a third wave of the virus, even as the country is in the process of exiting a lockdown that curbed its second wave.

IDF medical staff prepare to open two coronavirus wards in Haifa’s Rambam Medical Center in Haifa in an undated photograph. (Israel Defense Forces)

“There are signs pointing to a third wave,” said former Health Ministry director Moshe Bar Siman Tov on Wednesday. While cases have fallen sharply, the average number of people that each patient is infecting has risen.

On Thursday, the government met to discuss continuing further stages of reopening, including gyms, shopping malls and school grades 5 and 6,  as well as a possible nightly curfew to address concerns of resurgence. No decision on the moves was expected until next week.

Among some Israeli experts, the US research has increased nervousness about the reopening of gyms and eateries, and prompted suggestions that the government should rethink plans and push these venues to the end of the exit strategy in January or February.

“The reopening of indoor gatherings should be a last stage of reopening,” Ronit Calderon-Margalit, a prominent Hebrew University epidemiologist, told The Times of Israel, saying that it didn’t make sense to raise the risk infection for the sake of recreation.

Prof. Arnon Afek of Sheba Medical Center (Shai Pereg).

Former Health Ministry director-general Arnon Afek said that while today’s Israeli statistics don’t point to a third wave, they should prompt either a slower-than-planned reopening or increased enforcement of rules to cut infection.

He thinks the new research should shape the conversation by highlighting the risks of indoor spaces. Afek, deputy-director of Sheba Medical Center, said: “It is a warning sign about the danger of closed places for spreading the virus, and an important one for Israel given that the summer weather has enabled people to be outdoors lots but winter is coming and people will be spending more time indoors in closed spaces.”

Epidemiologists have been trying, since the pandemic began, to work out how far various policy steps will increase or reduce infection. During the now-lambasted reopening after Israel’s spring lockdown, officials admitted they were taking a “trial and error” approach.

A waitress wearing protective equipment as a coronavirus precaution (vichie81 via iStock by Getty Images)

Now, the American researchers say they have the “secret ingredient” that makes such calculations possible. It is cellphone data that shows the hour-to-hour movements of some 98 million people in the 10 largest US metro areas, calculating where they went, how crowded the places were, and how long they stayed. They didn’t include schools, as they were unable to track children under age 13.

The team was drawn from Stanford University, Northwestern University, Microsoft Research and the Chan Zuckerberg Biohub. It built a model that, it says — despite not actually cross-referencing which cellphone users were diagnosed with the virus — accurately shows how changes in a population’s movement patterns impact the level of coronavirus transmission.

This meant that ahead of changes in policy, like the reopening of restaurants, they managed to predict the impact it would have on coronavirus transmission, and found their figures matched numbers of actual cases.

Comparing their data, gathered over two months starting in March, to pre-pandemic movement patterns, they concluded that virus-fighting steps saved many lives.

Stanford University computer scientist Jure Leskovec (courtesy of Jure Leskovec)

“If we had just kept moving around as we moved in February before the lockdown, then during March, over just one month, around a third of a city’s population would’ve become infected,” Jure Leskovec, senior author of the report, told The Times of Israel.

But more relevant for now are the conclusions drawn by the researchers on where infection spreads, which highlight the riskiness of the very venues that Israel is about to reopen. Leskovec said the data also suggests smart ways to reopen with limited infections.

“Our work highlights that it doesn’t need to be all or nothing,” said Leskovec, a Stanford University computer scientist, arguing for strong measures to limit capacity in newly opened venues. He is confident that based on the correlations his team has seen between movement and infection, this will work.

The ongoing exit from Israel’s second lockdown has been characterized, until now, by the limiting of capacity. “We are allowing four customers at a time, not more,” stressed Prime Minister Benjamin Netanyahu, ahead of the November 8 opening of street-side stores.

People shop on the first day of the reopening of street shops on Jaffa Street in downtown Jerusalem on November 8, 2020. (Yonatan Sindel/Flash90)

However, in the final discussions of details for upcoming exit strategy stages, which tend to happen in the hours and days before they take effect, there is likely to be heavy pressure from businesses against strict capacity limits. While stores can manage with the four-customer limit keeping others in a line at the door, gyms, restaurants and cafes, where people stay for longer, say that operating profitably will be difficult with limits.

Leskovec says such limits are essential. According to his calculations, had American cities fully opened restaurants after the first month of coronavirus measures, some 6% of their populations would have become infected from this step alone.

Limiting restaurant capacity to 20% of capacity can prevent 80% of transmissions, he said, adding that as tables are only generally full at peak times, the loss of business would be around 40%.

This kind of limited-capacity model should be adopted across indoor spaces, Leskovec suggests, stressing that it will require people to rethink their schedules, and get out of the habit of visiting places at peak times — a habit that is ingrained in Israel where for example, supermarkets are crammed on Thursday nights and Fridays, ahead of Shabbat.

“A key here is trying to spread out a society’s off-peak times,” Leskovec said. “It’s about finding the right balance between economy and safety.”

The study identified another challenge relevant to Israel, where infections are disproportionately high in two minority groups that tend to be poorer than general society: Arabs and the ultra-Orthodox. Leskovec’s study suggested that, at least in the American context, the environment and lifestyle of poorer people puts them at more risk.

He sees their movement patterns as a key reason that explains why in eight out of ten cities studied, transmission rates were significantly higher in areas with low income than areas with high income.

“Before our research, the main hypothesis in the US was that poor people suffer more because of preexisting conditions, but we’ve shown they can’t reduce mobility as much as richer people,” he said, noting that they are less likely to have work-from-home jobs, tend to live in more cramped neighborhoods, and, as they are less likely to have their own transportation, they shop in local stores that are smaller and more crowded.

The phone data showed that the average grocery store visited by lower-income individuals had 59% more hourly visitors per square foot, and their visitors stayed 17% longer on average.

People shop for groceries at the Rami Levy supermarket in Modi’in in central Israel in September, just after lockdown was reimposed. (Yossi Aloni/Flash90)

“One visit to a grocery store is twice as dangerous for lower income that higher income person,” he said, explaining: “They move around more and when they go to get groceries, it’s at a store with more infected people, more density, and stay there longer.” He said that policymakers should find ways to reduce the risks for lower-income people going about their routine.

Nadav Davidovitch. (courtesy of Ben-Gurion University)

The new research is interesting, said Nadav Davidovitch, epidemiologist at Ben-Gurion University of the Negev and a leader of Israel’s doctors union. But he he said that while it’s a model that may offer valuable insight, it shouldn’t be treated as an entirely accurate picture, nor should it be seen as an alternative for traditional epidemiological research.

Davidovitch is cautious about drawing inferences for Israel, saying there are differences between interaction patterns in different countries, yet he thinks it highlights the value of having nuanced rules long after a total lockdown.

“Israel’s second lockdown reduced mobility not to 30% of the norm, like first one, but to 40%, and there were some people asking what the point was,” he commented. “What we’re seeing suggested by this research is that we don’t need black or white, but rather to reduce encounters and, if this happens, you can continue and live with the pandemic.

“This emphasizes that when you reduce encounters you don’t need them to be down to zero. Rather a substantial reduction still gives most of the advantages.”

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