The Centers for Disease Control (CDC) has been misleading the general public on how often the data shows the novel coronavirus spreading from person-to-person in outdoor settings, The New York Times argued in a report Tuesday.
Only weeks ago, in late April, CDC Director Dr. Rochelle Walesnky said that less than 10% of documented COVID-19 transmission cases, as recorded in various studies, can be attributed to outdoor transmission. Dr. Walesnky used this figure when making the point that data suggests “most of transmission is happening indoors rather than outdoors.”
But The New York Times reports that the 10% figure is “almost certainly misleading” and also appears to be based partly on misclassified data from Singapore construction sites.
According to The New York Times, one study of 10,926 global coronavirus transmission cases recorded 95 outdoor cases, all of which were in Singapore construction sites. A separate study found four instances of outdoor transmission, out of 103 total cases of transmission, and all four of the cases were also in Singapore-based construction sites.
Those Singapore cases, however, may have occurred in enclosed spaces on construction sites rather than in open areas. From The New York Times:
The Singapore data originally comes from a government database there. That database does not categorize the construction-site cases as outdoor transmission, Yap Wei Qiang, a spokesman for the Ministry of Health, told my colleague Shashank Bengali. “We didn’t classify it according to outdoors or indoors,” Yap said. “It could have been workplace transmission where it happens outdoors at the site, or it could also have happened indoors within the construction site.”
As Shashank did further reporting, he discovered reasons to think that many of the infections may have occurred indoors. At some of the individual construction sites where Covid spread — like a complex for the financial firm UBS and a skyscraper project called Project Glory — the concrete shells for the buildings were largely completed before the pandemic began. (This video of Project Glory was shot more than four months before Singapore’s first reported Covid case.)
Because Singapore is hot year-round, the workers would have sought out the shade of enclosed spaces to hold meetings and eat lunch together, Alex Au of Transient Workers Count Too, an advocacy group, told Shashank. Electricians and plumbers would have worked in particularly close contact.
In response to The New York Times report, Dr. Walensky said that the less-than-ten-percent figure for outdoor cases was pulled from a top-line meta-analysis published in the Journal of Infectious Diseases. “All studies that were included in the systematic review said less than 10% of cases were transmitted outdoors,” said Dr. Walesnky.
In reference to that same claim, the Times argues, “[s]aying that less than 10 percent of Covid transmission occurs outdoors is akin to saying that sharks attack fewer than 20,000 swimmers a year. (The actual worldwide number is around 150.) It’s both true and deceiving.”
The CDC, however, told The New York Times in a statement: “There are limited data on outdoor transmission. The data we do have supports the hypothesis that the risk of outdoor transmission is low. 10 percent is a conservative estimate from a recent systematic review of peer-reviewed papers. CDC cannot provide the specific risk level for every activity in every community and errs on the side of protection when it comes to recommending steps to protect health. It is important for people and communities to consider their own situations and risks and to take appropriate steps to protect their health.”