The outbreak initially surfaced in northern China, prompting the World Health Organization (WHO) to issue an "official request" to China for comprehensive information regarding the spike in respiratory illnesses and reported clusters of pneumonia, particularly among children.

Chinese authorities, including the National Health Commission, attribute the surge to the relaxation of COVID-19 restrictions and the concurrent circulation of known pathogens such as influenza, mycoplasma pneumoniae (common among younger children), respiratory syncytial virus (RSV), and SARS-CoV-2, the virus responsible for COVID-19.

The WHO revealed that northern China has witnessed a substantial rise in influenza-like illnesses since mid-October compared to the same period in the past three years. As part of its existing systems, China routinely monitors trends in influenza, influenza-like illnesses, RSV, and SARS-CoV-2, reporting to platforms like the Global Influenza Surveillance and Response System.

The alarm was raised on November 21 when both media and ProMED (Program for Monitoring Emerging Diseases) reported clusters of undiagnosed pneumonia in children in northern China. The WHO emphasized the need for more information to ascertain if these cases are linked to the overall surge in respiratory infections or represent isolated incidents.

ProMED, known for its pivotal role in alerting the world about the emergence of SARS-CoV-2 in December 2019, has now become the early warning system for this "walking pneumonia." The organization reported the absence of cough but highlighted the presence of high fever and pulmonary nodules, leading to severe health implications for affected children.

Eric Feigl-Ding, an epidemiologist and health economist, disclosed that pediatric hospitals in Beijing and Liaoning, separated by 800 km, are inundated with sick children. Consequently, several schools have been forced to close due to the outbreak, adding a layer of complexity to the ongoing healthcare crisis.

As concerns grow, the WHO awaits further details from Chinese health authorities on the circulation patterns of known pathogens and the strain on healthcare systems, underscoring the urgent need for global collaboration and transparency in managing this unforeseen health crisis.