A mystery pneumonia is reportedly tearing through schools in China.
Hospitals in Beijing and 500 miles northeast in Liaoning are among those 'overwhelmed with sick children,' while school classes were 'on the verge of suspension', according to local news reports.
The children are presenting with unusual symptoms that include inflammation in the lungs and a high fever - but no cough or other symptoms usually associated with flu, RSV and other respiratory illnesses.
The alert was issued late on Tuesday via ProMed - a large, publicly available global surveillance system that monitors infectious diseases.
It was a ProMed notification back in December 2019 that brought a mystery virus, later given the name of Covid, to the attention of many doctors and scientists, including officials at the World Health Organization.
Hospitals in Beijing and Liaoning are among those 'overwhelmed with sick children,' while school classes were 'on the verge of suspension'
Hospitals in Beijing and almost 500 miles northeast in Liaoning
The source for the alert was a report by the Taiwanese outlet FTV News, which added that 'parents questioned whether the authorities were covering up the epidemic.'
China was roundly criticized for covering up the original SARS epidemic in 2003 and the Covid pandemic in late 2019 - which were both novel viruses that cause pneumonia.
But the new outbreak could be related to Mycoplasma pneumoniae, also known as walking pneumonia, which is reportedly growing in China as the country goes into its first winter without strict Covid lockdowns in place.
The US and UK also saw spikes in diseases like RSV and flu after pandemic rules lifted.
FTV News reported that Beijing Children's Hospital was still overcrowded in the early morning Wednesday.
'The situation in Liaoning Province is also grim,' FTV News said.
The lobby of Dalian Children's Hospital is reportedly full of sick children receiving intravenous drips.
There are also long queues of patients at the Traditional Chinese Medicine Hospital and the Central Hospital.
A staff member of Dalian Central Hospital said: 'Patients have to wait in line for two hours, and we are all in the emergency department and there are no general outpatient clinics.'
Some school classes have been canceled altogether. Not only are all students sick, but teachers are also infected with pneumonia.
Mr Wei, a Beijing citizen, told FTV News: 'Many, many are hospitalized. They don't cough and have no symptoms. They just have a high temperature (fever) and many develop pulmonary nodules.'
An editor's note by ProMed said: 'This report suggests a widespread outbreak of an undiagnosed respiratory illness... It is not at all clear when this outbreak started, as it would be unusual for so many children to be affected so quickly.
'The report does not say that any adults were affected, suggesting some exposure at the schools.
'ProMed awaits more definitive information about the etiology and scope of this concerning illness in China.'
Pneumonia is an infection that affects one of both lungs, which can be deadly. The air sacs in the lungs may fill with fluid or pus.
Generally, pneumonia is not contagious, but the respiratory viruses and bacteria that lead to it are.
Walking pneumonia, which typically affects younger children, causes a sore throat, tiredness and a cough that can last up to months.
In serious cases, the illness can become pneumonia.