The World Health Organization has begun investigating a respiratory illness in Chinese children. The WHO  is requesting detailed information from Chinese rulers on the increase in pneumonia among the country’s children, using language similar to a January 5, 2020, pre-pandemic missive regarding COVID-19.

The cause of these cases is unclear but some health experts are attributing it to a common and temporary aftereffect of lifting lockdown restrictions. The unanswered questions around the new infections have led others to draw parallels with the early days of the COVID-19 scamdemic.

Officials from China’s National Health Commission have reported an increase in respiratory illness at a November 13th press conference, the WHO said in a Wednesday news release. On Tuesday more reports of pneumonia of an unknown cause in children in northern China were received.

The WHO on Wednesday said it had requested additional information from the Eastern superpower, including patient lab results and data on the circulation of known respiratory pathogens like flu, COVID-19, and RSV. It also requested details on how such circulation is affecting healthcare system capacity.

Children’s hospitals in Beijing, Liaoning, and elsewhere in the country are “overwhelmed with sick children,” with schools “on the verge of suspension,” according to a Tuesday bulletin from the International Society for Infectious Diseases, citing local news reports. -Fortune

While these cases of illness are “concerning,” the ruling class states that it isn’t new.

The first suspicion of Dr. Michael Osterholm, the director of the University of Minnesota’s Center for Infectious Disease Research and Policy (CIDRAP) is that this is “a series of already recognized respiratory pathogens,” due to the fact that illnesses are reportedly occurring in children. “If it was a new pathogen, it would be showing up in kids and adults equally, ” he told Fortune.

Dr. Amesh Adalja, an infectious disease specialist and senior scholar at the Johns Hopkins Center for Health Security, agreed, telling Fortune that while information is still incredibly sparse, “it would not be surprising if it’s a constellation of various respiratory pathogens together causing clusters of illness.” Some reporting has pointed to mycoplasma pneumoniae, an atypical bacteria that can cause lung infection, as a potential cause, he said. It’s commonly known as “walking pneumonia.”

Schools in Beijing are also reporting high levels of absenteeism, even dismissing entire classes for at least a week if some students are ill and warning parents to be extra cautious, according to a report by Al Jazeera.