China’s covid data is bad. An epidemiologist says that is making the surge nearly impossible to track.

Jonathan Lambert

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China’s zero-covid policies created a coronavirus tinderbox; it may have just ignited. But accurately tracking this conflagration of covid has become virtually impossible.

Years of strict lockdowns kept infections down but also prevented the buildup of immunity via infection. That immunity hole could have been filled by a robust vaccination campaign, but the country used less effective vaccines than other parts of the world and failed to reach those at highest risk of serious disease.

Now, as China’s government abandons covid control measures, the country with perhaps the largest population of immunologically susceptible people on the planet is facing a potentially catastrophic situation.

Earlier this month, China dismantled much of its testing system, and last week the government stopped reporting daily covid data, forcing epidemiologists to rely on anecdotal reports to understand where in the country the virus is spreading, and the damage left in its wake.

Those anecdotal reports paint a dire picture. Leaked hospital videos show an unprepared healthcare system buckling under pressure. Crematoriums are reporting a surge in demand as some models suggest that 9,000 people are dying each day in the country.

The Chinese government says that only about 5,200 have died of covid throughout the entire pandemic, with just about a dozen this month.

Grid spoke with epidemiologist Katelyn Jetelina, a public health researcher and author of the newsletter Your Local Epidemiologist. Jetelina has been closely following the situation in China, including how epidemiologists approach tracking an outbreak with scant official data and what impact this surge could have on the people of China and the world.

This interview has been edited for length and clarity.

Grid: What do we know about the current covid outbreak in China? What’s your sense for the reliability of reporting on cases, hospitalizations and deaths in China?

Katelyn Jetelina: We really know very little. And that is because the government has stopped reporting cases, hospitalizations, deaths. I think that they have reported a handful of genomic surveillance sequences, but certainly not enough to be helpful right now. So we’re really dependent on our epidemiology 101 knowledge about how viruses spread and how much we know about SARS-CoV-2, as well as anecdotal reports on the ground. And there are plenty of those showing that that situation in China is very grim right now.

G: Given that lack of official numbers, how can epidemiologists gauge the scope of the outbreak there?

KJ: That’s a really good question. Currently what we’re doing is, one, relying on modeling. Right now, we know that X percent of this population is vaccinated with this [Sinovac and Sinopharm] vaccine, how many are susceptible and what have we seen elsewhere with omicron. So we can use that information to model what might happen. [One recent model suggests half a million could die by April without any restrictions; another estimates 1.7 million deaths by the end of April.]

We also have anecdotal reports from physicians on the ground and things like videos inside of hospitals being leaked — which are really important, since we always need to pair up qualitative data with quantitative numbers to give us kind of a full contextual framework of what’s going on.

And third, we’re relying a lot on travel surveillance. Some countries that are testing on arrival from China are also doing genomic sequencing. Italy, for example, is reporting genomic surveillance of their travels, and with countries doing that, we have a pretty good understanding of what variant is circulating in China.

Some countries are starting to test every single traveler. There was a report from Milan that about 50 percent of travelers on a plane [from China] tested positive. I think a lot of countries are scrambling right now to put the puzzle pieces together to figure out if this virus is changing in China and how it’s changing.

G: Some experts are worried that such widespread transmission might spawn new variants. What’s your sense of that risk?

KJ: Every time the virus jumps from person to person, we give it the opportunity to mutate. And the floodgates in China have been opened up; it gives the virus more opportunity to mutate. China has nearly 20 percent of the global population; that’s a lot of times the virus is jumping from person to person.

But I think it’s important to highlight that this is more of a possibility rather than a probability. And that’s because transmission is high everywhere; it’s jumping from person to person very quickly in the United States.

The other thing I think we need to keep in mind is that the variant that we think is currently causing the wave in China, which is BF.7, is a couple evolutionary steps behind what’s currently spreading in the United States and most of the world. A new variant could erupt from China, but that doesn’t necessarily mean it will be able to dominate in places where XBB, for example, is circulating — like the United States. There’s a lot of things that would kind of have to go wrong for the outbreak in China to have major variant implications for the globe. But it is a possibility.

G: Does China have the genomic surveillance infrastructure to track variant evolution? And if they do, are they sharing that data?

KJ: They do have the capability of genomic sequencing. If they’re doing PCR tests, it’s just an added little step. And I have every reason to believe that they are doing that, or they have the capability of doing it. They’re just not sharing it, which is an international responsibility, to be frank.

G: If China isn’t sharing those data, how can the U.S. and other governments track variant evolution?

KJ: We won’t have access to any of the testing done in China, even if we require a pre-departure test to come to the United States. But what we can do — and what a lot of countries are doing, including the United States — is test people once they arrive. I think enhanced surveillance of PCR cases with travel history to China is worthwhile. That’s one way we can try to find new variants.

The challenge with this, at least in the United States, is we don’t have a very robust and dynamic surveillance travel program. It’s kind of like finding a needle in the haystack. But I still think it’s worthwhile to ramp that up as much as possible.

G: Do you think requiring travelers from China to show a negative covid test before boarding U.S.-bound flights will actually have any kind of impact in the U.S.?

KJ: I think that is the major debate now among scientists. I think everyone agrees it’s not going to stop transmission, but the question is how much it will delay transmission. And if you delay it, how much impact will that have?

I’m not optimistic about this policy, mostly because if we’re buying time, it’s really only useful if we actually did something with that time, and it’s not clear what that plan would be. What are we going to change in the next week or two with that bought time? Every policy like this is incredibly difficult, but to me, epidemiologically, it’s just not adding up.