Uh, what: WHO official says it’s “very rare” for asymptomatic patients to spread coronavirus

Two headlines, submitted for your approval. One…

…and two:

The first was published by CNBC today. The second was published by Time magazine three days ago. How are our scientific experts still at odds over a fact as basic as whether asymptomatic patients are infectious? There are nearly two million confirmed cases of COVID-19 in the U.S. alone available for study.

Granted, it’s a novel virus so some of their early impressions were bound to be revisited. We can forgive them (sort of) for initially believing that transmission happened by touching contaminated surfaces instead of through the air. We can even forgive them (not really) for their early skepticism towards wearing masks. But how can there be a dispute over one of the disease’s most distinguishing characteristics, its supposed transmissibility by people not suffering symptoms? This was, I thought, essentially the entire reason why COVID-19 was so hard to control and why nothing short of shutting down the economy could slow it down. We couldn’t stop it by quarantining the visibly sick because it wasn’t just the visibly sick who were passing it around.

Was it? From CNBC:

Preliminary evidence from the earliest outbreaks indicated that the virus could spread from person-to-person contact, even if the carrier didn’t have symptoms. But WHO officials now say that while asymptomatic spread can occur, it is not the main way it’s being transmitted.

“From the data we have, it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual,” Dr. Maria Van Kerkhove, head of WHO’s emerging diseases and zoonosis unit, said at a news briefing from the United Nations agency’s Geneva headquarters. “It’s very rare.”

“What we really want to be focused on is following the symptomatic cases,” Van Kerkhove said. “If we actually followed all of the symptomatic cases, isolated those cases, followed the contacts and quarantined those contacts, we would drastically reduce” the outbreak.

I thought we urgently needed to ramp up testing because random testing of seemingly healthy people was the only way to catch some of those asymptomatic patients before they passed the virus along. Now they’re telling us that … we mainly just need to test the symptomatic cases after all? What?

Is this some new Chinese disinformation that the WHO has been tasked by Beijing with propagating?

Here’s the story that accompanies the Time headline I featured up top:

In a study published June 3 in the Annals of Internal Medicine, researchers at the Scripps Research Translational Institute reviewed data from 16 different groups of COVID-19 patients from around the world to get a better idea of how many cases of coronavirus can likely be traced to people who spread the virus without ever knowing they were infected. Their conclusion: at minimum, 30%, and more likely 40% to 45%.

Such so-called asymptomatic spread is unique for a respiratory virus; most cause symptoms and disease once they infect their hosts. SARS-CoV-2, the virus responsible for COVID-19, is, however, particularly wily because it can also infect hosts silently and use them as unwitting pawns in its infectious campaign. “The range we found is extraordinarily high,” says Dr. Eric Topol, director and founder of the Institute and one of the authors of the paper. “That means the range of what can happen with SARS-CoV-2 is from no symptoms to [death]. That’s not at all similar to any virus or pathogen we’ve experienced that has killing potential in the past. What we have here is an extraordinary spectrum, including this quiet, stealth mode of infecting somebody.”

Note the distinction between saying “X percent of coronavirus patients have no symptoms” and “X percent of coronavirus transmissions came from patients who have no symptoms.” The CDC estimates that 35 percent of patients are asymptomatic but that’s not strictly inconsistent with the WHO’s new conclusion. It could be that 35 percent get infected, never know, but also don’t pass it on to anyone else. The significance of Topol’s study is that it claims, or seems to claim, that a huge majority of transmissions are coming from asymptomatic patients.

But I don’t know. When Topol was asked about the WHO statement today on Twitter, he seemed to take a middle-ground view. It may be that the WHO is right, that infected but asymptomatic people are infecting others only very rarely, yet the total population of asymptomatic patients may be so enormous that that still adds up to a large percentage of total infections overall:

I don’t know how to square that with the CDC estimate, though. One would think you’d need a huge population of asymptomatic patients to account for 40 percent of all transmissions if they’re infecting other people only infrequently. And I can’t understand why asymptomatic people would be so much less likely to infect others if, as studies have shown, they have as much of the virus in their system as symptomatic patients do. Someone who’s symptomatic may be more prone to expel the virus for greater distances than someone who’s not symptomatic (e.g., through a hacking cough), but surely talking face-to-face with an asymptomatic carrier in a confined space for some length of time should create a meaningful risk. Except no, I guess, not if you believe the WHO.

Watch Kerkhove speaking today in the clip below. At one point she distinguishes between true asymptomatics and people with merely “mild” symptoms. Maybe all she’s saying here is that most of the people whom we think of as “asymptomatic” actually do have some sort of slight reaction to the disease — “COVID toes” or a day of muscle aches or what have you. Those people can transmit the disease. But the true asymptomatics? They might be rare, and evidently they infect others rarely. Why that might be, I have no idea since she doesn’t speculate.

After you’re done with the clip, read this fascinating and potentially important Wall Street Journal story about infection patterns across the country. The Journal wanted to test the theory that the virus spreads most easily in high-density urban centers like New York City so it looked at transmission rates in different regions. The verdict: It’s *not* city density that’s the key variable. It’s the frequency with which people live together in crowded households, with extended families under the same roof particularly vulnerable. “Remote, rural hamlets where extended families live under the same roof have turned deadlier than some of the densest blocks of Manhattan or Chicago,” the WSJ reported. “In both contexts, the virus has zeroed in on crowded homes, sometimes wiping out generations in a matter of days.” Among U.S. counties with 50 or more coronavirus cases, the top 10 percent in terms of the highest rates of crowding accounted for 28 percent of all COVID-19 cases. This has always been the core argument for adopting centralized quarantine, as China did and some other Asian nations have done: Once someone in a family household gets sick, the only way to prevent a chain reaction is to get that person out of the home and into a hotel room or some other facility so that they can recover without infecting others. We’ll probably never do it here because, well, we’ve given up on fighting this disease by and large. But we should.

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