How bad is China’s Covid outbreak? It’s a scientific guessing game

In Hong Kong, one team of researchers pored over passenger data from five Beijing subway lines to determine the potential spread. In Seattle, a group of modelers tried in vain to reverse-engineer an unverified government leak detailing case numbers from Chinese health officials. In Britain, scientists are coming up with their own efficacy estimates of Chinese vaccines.

They are all attempting to understand the same things: How quickly is the virus spreading in the country? How many people are dying? Could China be the source of a new and dangerous variant?

As scientists sift through varied sources of shaky information, they are bracing for potentially catastrophic outcomes. Barring new precautionary steps, some worst-case estimates suggest that COVID could kill as many people in China in the next four months as it has Americans during the entire three-year pandemic.

Without satisfying answers, some countries are putting limits on Chinese travelers, albeit based in part on unfounded fears or political motivations. The United States, Italy and Japan have said they will require a negative COVID test for those coming from China, citing concerns that the surge in cases in China could produce new, more threatening variants.

While researchers and virologists said the new measures would most likely do little, if anything, to blunt the spread, the policies reflect the limited visibility into the outbreak.

Until this month, the world seemed to have a reasonably clear understanding of what was happening with the virus in China. The ruling Communist Party proudly published low daily case numbers and deaths as a testament to its stringent “zero COVID” policy. A countrywide system of lockdowns, quarantines and mass testing largely kept the virus at bay.

But in early December, the government abruptly abandoned “zero COVID,” leaving the scientific community largely in the dark.

“Nobody, nobody has a clue,” said Siddharth Sridhar, a clinical virologist with a focus on emerging infectious diseases.