Face masks and social distancing are again being recommended in China in a chilling echo of the early days of Covid.

Some media reports say the country is grappling with a spike in pneumonia, dubbed 'white lung syndrome' because of the way lung damage shows up on scans, among children that has been attributed to a rebound in respiratory illnesses rather than an entirely new virus.

China had one of the most brutal and longest lockdowns of any country in the world which the WHO says robbed children of vital immunity against seasonal illnesses.

Chinese Health Ministry spokesman Mi Feng reportedly urged people to again consider social distancing and masking up to avoid the disease

The world was first alerted to the mysterious outbreak in China on November 21, when the disease surveillance system ProMED issued a notification about reports of an 'undiagnosed pneumonia' in China.

China also shared data that showed the country had been recording an increased number of children sick with mycoplasma pneumoniae — bacteria that causes mild infections of the respiratory system — since May.

Concerns have been raised that people are being sickened by a disease — similar to the early stages of the Covid outbreak.

CNN says hospitals in Beijing and northern China are grappling with a surge of children with respiratory illnesses as the country enters its first winter since relaxing stringent Covid-19 controls nearly one year ago.

Wait times to see doctors stretch for hours, with hundreds of patients queuing at some children’s hospitals in major cities across northern China, according to CNN reporting and Chinese state and social media.

An official at the Beijing Children’s Hospital reportedly told state media on November 21 that the current average of more than 7,000 daily patients “far exceeds the hospital’s capacity.”  The largest pediatric hospital in nearby Tianjin broke a record on November 18, receiving more than 13,000 children at its outpatient and emergency departments, according to a local state-run outlet.

The WHO asked China for more information on November 22 after groups including the Program for Monitoring Emerging Diseases (ProMED) reported clusters of undiagnosed pneumonia in children in north China.

Reuters reports that as per the rule, China responded to the WHO within 24 hours.  The WHO had sought epidemiologic and clinical information as well as laboratory results through the International Health Regulations mechanism.

The data suggests the increase is linked to the lifting of COVID-19 restrictions along with the circulation of known pathogens like mycoplasma pneumoniae, a common bacterial infection that typically affects younger children and which has circulated since May.

Influenza, respiratory syncytial virus (RSV) and adenovirus have been in circulation since October.

The agency reportedly does not advise against travel and trade as they have been monitoring the situation with authorities.

China continues to insist that flu and the usual winter bugs are to blame for the latest outbreak, rather than a new virus, and can cope with the spike in sickness.

Local authorities, however, have already called upon to open more fever clinics and promote vaccine uptake among children and the elderly.

Some media reports say the US faced a similar wave of illnesses last winter in its own 'exit wave' from the pandemic with many pediatric units overflowing and so did the United Kingdom.

Experts have also suggested that the fact mostly children are being sickened in this outbreak suggests the diseases causing it are ones adults have already been infected by and have immunity against.