Amid China's massive COVID surge, 42% of people on a flight tested positive

Enlarge / A passenger wearing protective clothing during the COVID pandemic -19 waits to board a domestic flight at Shanghai Pudong International Airport on January 3. Getty | HECTOR RETAMAL / AFP

Although China has largely abandoned reporting of COVID-19 cases, evidence of its massive wave of infection is readily emerging at airports outside its borders.

On a Dec. 26 flight from the southeast city of Wenzhou to Milan, Italy, 42 percent of the 149 passengers on board tested positive for COVID-19 upon arrival, according to a report. study published Thursday in the journal Eurosurveillance.

The Italian researchers behind the study also looked at the test positivity rates of three other flights from cities in eastern China to Italy, two to Milan and two to Rome, all at the end of December. Collectively, 23% of passengers on the four flights (126 out of 556 passengers) tested positive for SARS-CoV-2. The other three flights had positivity rates of 19%, 11% and 14%.

The passengers were tested either with rapid antigen tests or with PCR tests. Positive antigen tests were confirmed by PCR tests. The tests most likely captured people with mild or asymptomatic cases, as well as those who had recently recovered. PCR tests can remain positive for weeks after an infection.

Similar to the Italian data, the Washington Post reported about a week ago that it had seen data from the Korea Disease Control and Prevention Agency indicating that 23% of short-term visitors from China in Korea (314 out of 1,352 tested at the airport) were positive for SARS-CoV-2 between January 2 and 6.

The rates point to massive infection in China, which is expected, but not well documented. When China abruptly abandoned its zero COVID policy last month, it abandoned mass testing and largely gave up reporting cases. During this time, the virus has spread through a population that is, as the Italian researchers note, "a highly vaccinated but infection-naive population".

Current models estimate that there could be 1.5 million new infections per day in China and more than 1 million people could die in the coming weeks. Health experts are particularly concerned about the spread of the disease amid the upcoming Lunar New Year on January 22, when tens of millions of people in China travel to see their families for the festivities. The move is expected to shift high transmission from large cities to more vulnerable rural areas.

Benjamin Cowling, an epidemiologist at the University of Hong Kong, told the Washington Post that infection rates so far are "very much in line with predictions that the majority of people in major cities have already been infected".

Good news is that Italian researchers sequenced the entire virus genome of 61 passengers and, in this sample, found no new or alarming variants. Sampling revealed the omicron BA.5.2, BF.7 and BQ.1.1 sublines, which have been seen elsewhere. The data matches what has been reported elsewhere and in China.