Mysterious pneumonia has reportedly broken out in schools in China with hospitals in Beijing and 500 miles north-east in Liaoning “overwhelmed with sick children”.

Children have unusual symptoms that include inflammation of the lungs and a high fever, but not a cough or other symptoms commonly associated with influenza, RSV, and other respiratory illnesses.

The alert was issued late Tuesday through ProMed, a large, publicly available global surveillance system that tracks infectious diseases.

ProMed had informed in December 2019 again about a mysterious virus, later named Covid.

However, the new outbreak could be related to Mycoplasma pneumoniae, also known as walking pneumonia, which is reportedly on the rise in China as the country goes through its first winter without strict Covid lockdowns.

The US and UK also saw increases in illnesses such as RSV and influenza after the pandemic rules were lifted.

The FTV News network reported that the Beijing Children’s Hospital was still full early Wednesday with the situation in Liaoning province also grim, it said.

The lobby of Dalian Children’s Hospital is reportedly filled with sick children receiving intravenous drugs. There are long lines of patients at both the Traditional Chinese Medicine Hospital and the Central Hospital.

The alert issued by ProMed stated that “this exposure suggests a widespread outbreak of an undiagnosed respiratory disease. It is not at all clear when this outbreak started, as it would be unusual for so many children to be affected so quickly.”

“ProMed awaits more definitive information about the etiology and scope of the disease in China,” the statement said.