The goal of this observational study is to answer a few questions about respiratory tract infections in South African children: 1. How do children with COVID-19 and other respiratory (chest, throat, ear or nose) germs show symptoms? What signs should be looked for, and which children are more likely to get seriously ill? Are there any new germs that haven't been discovered yet? Can immune cells in saliva predict which children will get more severe disease? 2. The body's immune response (soldier- cells) in blood and saliva (spit) will be studied. 3. What is the short-term effect of COVID-19 and other respiratory viruses/ germs on the breathing (lung function) of children? 4. What is the impact of respiratory germs on the quality of life in children and their families? The investigators aim to recruit a minimum of 250 children with respiratory pathogens.