Final answer:
The most frequent cause of pneumonia in children aged 6 months to 5 years is commonly viral, with respiratory syncytial virus (RSV) being very common, though Streptococcus pneumoniae is a significant bacterial cause as well.
Step-by-step explanation:
The most frequent cause of pneumonia (PNA) in children aged 6 months to 5 years is typically viruses, although bacterial pneumonia is also common. Among the viruses, respiratory syncytial virus (RSV) is the leading cause of viral pneumonia in this age group. However, bacterial pneumonia, particularly caused by Streptococcus pneumoniae (pneumococcus), is also prevalent with its own set of complications such as pneumococcal meningitis. When looking at various cases, for instance, Tracy, a 6-year old, was diagnosed with bacterial pneumonia caused by Haemophilus influenzae, another common bacterial pathogen in pediatric respiratory infections.