China logged 105 new Covid-19 cases, 102 of them locally transmitted, for July 29, up from 101 cases for Tuesday and marking more than 100 cases for two consecutive days for the first time in months.

Of the new infections, the national health commission (NHC) said, 96 were from the Xinjiang Uyghur Autonomous Region (XUAR) in the northwest and five from the northeastern province of Liaoning, two of the new hotspots for fresh Covid-19 cases in China.

One case was reported from Beijing, which has now recorded cases for three consecutive days, after not logging any for nearly three weeks.

The new outbreak in Dalian, the capital of Liaoning province, has been linked to a seafood company, health authorities have said.

The NHC, however, is yet to reveal the source of the new Covid-19 cluster in Xinjiang, which has been under heavy surveillance – and strict censorship of information – because of tension between ethnic Muslim minorities and central authorities.

Most cases in XUAR, which now has 418, have been detected in the provincial capital, Urumqi, where widespread nucleic acid testing has been ordered and some residential communities isolated.

In the northeastern city of Dalian, a 58-year-old man working with a local seafood company was the first to be diagnosed with Covid-19 in the latest outbreak.

The city has now logged 57 locally transmitted cases most of whom were either employees of Dalian Kaiyan World Seafood company or their family members, state media reported.

So far, cases related to Dalian have been found in other cities of Liaoning, and in other provinces of Heilongjiang, Jilin and Fujian, as well as in Beijing.

All the 344 people working at the company have been quarantined.

“A total of 17,595 medics have been mobilised to conduct nucleic acid tests at 2,698 testing sites across the city, with nearly 3.53 million samples collected by midnight Tuesday,” Zhao Lian, deputy director of the municipal health commission, told state media.

Meanwhile, one of China’s top epidemiologist has said the Covid-19 outbreaks in the central Chinese city of Wuhan – where the coronavirus first emerged in late 2019 — Beijing and Dalian share certain similarities “…as they all took place in the cold contaminated environment of seafood markets, and the virus may have infected people through aerosols.”

In an interview with Chinese media on Wednesday, Wu Zunyou, the chief epidemiologist of the Chinese Centre for Disease Control and Prevention, said their humid and low-temperature environment is more conducive for the coronavirus to survive.

Wu told Chinese media that an experiment carried out in Beijing’s Xinfadi market, which was linked to the June outbreak in the capital, in which a fluorescent powder was used to simulate the virus, showed that if the environment was contaminated, the virus could infect people through aerosols.

Workers could then pollute the environment after becoming infected, forming a mixed transmission mode, Wu added.

The Chinese media reports did not mention if Wu shed any light on the source of the new outbreak in Xinjiang.