As COVID-19 infections recede, China is witnessing a surge in new and mysterious respiratory illnesses, especially among children in the country's northern region. This illness has raised concerns among parents, government agencies and healthcare providers alike. The outbreak has flu-like symptoms and is characterized by lung inflammation and high fever. This has led to rise in hospitalizations in big Chinese cities, particularly in Beijing. Investigators are trying to find out the exact cause of this outbreak, but they suspect it may be due to a post-Covid phenomenon called 'immunity debt'. This debt stems from a reduction in exposure to common viruses and bacteria due to Covid-related lockdowns, which creates a surge in cases once these restrictions are lifted and people get exposed to these infections again. Since their immune system was not adequately challenged during lockdowns, it makes them more susceptible to these infections.