China claims Covid wave has peaked with severe cases, deaths falling fast

China’s health authorities have said the Covid wave is past its peak, with rapid decline in both severe cases and deaths in hospitals, but experts remain wary of the government’s official data.

According to China’s Center for Disease Control (CDC), the number of critically ill patients in hospital peaked in the first week of January, then rapidly declined by more than 70%. The number of deaths also reached its highest level that week, the data said.

Prof Chi Chun-huei, director of the centre for global health at Oregon University, said local officials were incentivised – via punishments and rewards – to under-report infection figures during the zero-Covid policy. Now that policy was gone, they were incentivised to exaggerate infection rates and under-report deaths.

“Most international experts know this very well – China’s statistics are very unreliable,” he said.

Related: Eight in 10 people in China caught Covid since early December, say officials

Covid cases have swept across China in recent months, escalating rapidly after the government suddenly ended its zero-Covid policy in early December 2022. Last week a senior health official said 80% of people had been infected in this wave, although it was not clear where the figures came from.

According to the data, there were 128,000 critically ill Covid patients in Chinese hospitals on 5 January, the highest number reached during this wave. It described a peak inside hospitals over the western new year, with almost 10,000 new critically ill cases a day from 27 December to 3 January.

By 23 January the total number of critically ill cases had dropped by 72% to about 36,000, it said.

The number of deaths in hospitals reached their highest point on 4 January, with 4,273 recorded, before falling 79% by 23 January to 896.

The CDC said the number of visits to fever clinics peaked at 2.867m on 23 December, before falling 96.2% to 110,000 on 23 January. A similar decline was observed in visits to rural clinics, with peaks around the same date, it said.

The data, published on Wednesday, was based primarily on hospital in-patients, giving some insight into the severity of the outbreak, but external health experts and observers have cautioned that it only shows one part of the true toll.

Related: Xi’s authority dented by sudden Covid U-turn, but grip on power is as strong as ever

China’s wave of infections hit major cities first, and there has been concern that travel for lunar new year could spread infections into regional areas. Reporting from inside China has already found apparent high rates of infection and fatalities that appear to exceed official reports.

With the end of zero-Covid, travel restrictions, mass testing, mandatory quarantine and other measures were wound back or dropped entirely. Data collection systems quickly fell far behind the reality on the ground, with fewer than 60 deaths officially recorded in the first few weeks until authorities updated the way deaths are attributed.

The notice from the CDC acknowledged that PCR testing was not keeping up with infections. Daily tests had dropped to 280,000 by Monday, down from 150m on 9 December, and 7.54m on 1 January. Some provinces had enacted systems for collecting the results of residents or allowing residents to self-report, but the figures were “affected by the willingness of residents to test”.

Previously several provinces or major cities had reported infection rates of 70-90%, but some analysts speculated such figures might have been over-inflated to suggest places were on the way to recovery.

Prof Antoine Flahault, director of the institute of global health at the University of Geneva, told the Guardian the figure of 80% total infection rate was “mostly plausible” and in line with global knowledge of Omicron’s attack rate.

“Having said that, to transfer that to mortality figures is highly difficult.”