Will the Tokyo Olympics be a superspreader event?

The Toyko Olympics appear unlikely to be a “superspreader” event, experts say — but that may be little comfort to people in Japan, where a combination of the delta variant and low vaccination rates is driving a new surge in Covid-19 cases.

Japan is currently living through its fifth wave since the start of the pandemic, while the Summer Olympics are finally being held after a one-year delay. The average number of daily new cases jumped from 1,400 in late June up to more than 5,700 as of July 29, nearly matching the previous peaks in May and January.

Those rising rates likely reflect a new wave of cases around the world, and in Asia especially, rather than anything specific to the Olympics. In fact, adjusted for population, Japan’s latest wave tracks quite closely with new cases across Asia. The infections currently being reported were also contracted up to two weeks ago, before the start of the Games, though personnel had begun to arrive.

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“I think what is going on in Japan right now is more reflective of the global picture of increased case numbers,” Andrew Nelson, a University of Minnesota pathologist who contributed to a CDC study on the Sturgis motorcycle rally told me in an email. “Related in part to the delta variant and importantly related to rates of vaccination in specific locales.”

The August 2020 rally in Sturgis, South Dakota, is generally thought of as an example of a superspreader event. It drew 460,000 people from around the US, and the CDC’s study linked it directly to clusters of cases in neighboring Minnesota, an example of how the rallygoers may have spread the virus elsewhere. But superspreader events are hard to quantify or define. Some experts have questioned how much we should focus on them, worrying they may distract from the many different ways Covid-19 spreads. Nelson called the term “problematic.”

And for the Olympics to actually become a quote-unquote superspreader event, a few things would have to go wrong. That’s not impossible, but it seems unlikely at the moment.

Japan isn’t a world leader in vaccination, but it has some other things going in its favor

With the Olympics underway, Japan has administered about 81 million shots, enough for roughly one-third of its people. That puts the country well behind the United States, the United Kingdom, Germany, and other wealthy nations in its vaccination drive. Japan is currently averaging about 1 million shots per day; at that pace, it would take another 4 months to reach 75 percent of the population, according to the Bloomberg vaccine tracker.

In the meantime, the Olympic Games probably don’t pose much of an additional threat to the rest of Japan, relative to the global trends they are already contending with.

The Olympians and people working at the Games have big advantages in reducing spread. Access is tightly regulated and tests are conducted regularly to catch cases early. The athletes themselves have high vaccination rates, with most teams reporting that 80 or 90 percent of participants got their shots.

An estimated 15,000 competitors are expected to stay in the Olympic Village at some point. Since July 1, 169 people affiliated with the Games have tested positive for Covid-19. No new cases were reported among athletes on Tuesday, even as Tokyo itself set a record for daily cases, one sign of disconnect with the surrounding area.

There is reason to be optimistic about the virus being contained at the Games themselves. A lot of precautions are being taken to do exactly that, starting with the public being barred from attending the events.

“Given the restrictions on movement, testing, masking, separation of the public from the official events, and other measures being taken, we can hope that any spread is limited somewhat,” Josh Michaud, associate director of global health policy at the Kaiser Family Foundation, said over email.

But the Games are still deeply unpopular with the Japanese public, surveys have found. People say they are worried about the effect on the current outbreak. And that worry isn’t necessarily unreasonable.

There are still risks to manage

Even if the risk of the Olympics being a superspreader event is relatively low, that doesn’t mean it’s zero. As Wafaa El-Sadr, director of the Global Health Initiative at Columbia University’s Mailman School of Public Health, put it to me: “Any time there are large numbers of people coming and mixing together, there is reason for concern.”

The athletes are going to socialize. They are performing rigorous physical activity, often near one another, without masks. Some of them are still unvaccinated. Workers are also entering and leaving the grounds.

The theoretical risk from the Games to Toyko and Japan at large would be, for starters, a cluster of cases among a group of athletes or workers. That is one thing experts say they’ll be watching for. While the Olympics are being closely monitored for Covid-19, it’s still possible to imagine a scenario in which the virus leaks into the community, exacerbating the surge already underway. There could be indirect effects as well.

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“Rates rising in Japan could also be impacted by the Games through more social mixing, bars and other venues being open, and essential workers having to increase front line and public facing work,” Chris Beyrer, a Johns Hopkins global health professor, said over email.

If rates increase in Japan more than would be expected from the delta variant alone, that would be an indicator the Games played a role.

Showing any direct link could be difficult, however, though Michaud said Japan has been “very good” with contact tracing so far. (He also pointed out that any spread associated with the Games would be “a politically sensitive issue,” which could hamper transparency.)

In the end, the experts I spoke with thought Japan’s lagging vaccination rates and the increased spread globally from the delta variant posed more of a risk to the nation than the Olympic Games.

“Given the infection control protocols in place around the Olympics and Japan in general,” Nelson said, “I think there is a very low probability that this observed increase is due to the Olympics and there is a very low probability that the Olympics will serve as a superspreader event.”

What’s not in doubt is that, as the rising cases in Japan already show, the coronavirus still poses a threat.

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