The surge in respiratory infections in young children in northern China is being driven primarily by known viral and bacterial infections and not by a novel pathogen, the World Health Organization (WHO) said late last week in an update.

Following a request for data and discussions with Chinese health officials on November 23, the WHO said the increase in outpatient consultations and hospital admissions of children in China is linked to increased circulation of pneumonia caused by Mycoplasma pneumoniae—commonly known as “walking pneumonia”—since May and a more recent uptick in respiratory syncytial virus (RSV), adenovirus, and influenza. That conclusion was based on data from enhanced surveillance systems for respiratory illnesses implemented in China in mid-October.