In the United States, the number of prospective studies that provide information on the frequency of hospitalizations for community-acquired pneumonia (CAP) in children is low.

Researchers from the United States conducted a population-based observational study in children under the age of 18 with CAP requiring hospitalization at 3 hospitals in Memphis, Nashville and Salt Lake City. The study did not include children who were recently hospitalized or patients with severe immunosuppression. To determine the pathogens responsible, blood and respiratory tract samples were taken. During the study, independent radiologists also evaluated the X-ray examination of the thoracic organs.

Between January 2010 and June 2012, 2,638 children (69%) of the 3,803 eligible patients were included in the study, and 2,358 of them (89%) had radiological signs of pneumonia. The researchers note that 70% of the children hospitalized with CAP were aged less than 4 years, 45% were children of less than 2 years, the average age of the hospitalized children was 2 years; 497 out of 2,358 children (21%) needed treatment in the intensive care unit; 3 children (less than 1%) died.

Among 2222 children with X-ray confirmation of pneumonia and with samples taken to test bacteria and viruses, viral or bacterial pathogens were identified in 1802 cases (81%); more than one virus was isolated from 1472 children (66%); bacterial pathogens identified in 175 children (8%); viruses and bacteria were isolated from 155 children (7%). The annual incidence of pneumonia was 15.7 cases per 10,000 children (95% confidence interval (CI) 14.9-16.5), the highest incidence among children under 2 years of age (62.2 cases per 10,000 children, 95% CI 57 6-67.1).

Respiratory syncytial virus has been shown to be a more common pathogen in children under 5 years of age compared to older children (37% vs 8%), as well as adenovirus (15% vs 3%) and the human metapneumovirus (15% vs 8%). Mycoplasma pneumonia was more common in children aged 5 years and older compared to younger patients (19% vs 3%). Only 4% of children had Streptococcus pneumoniae.

Thus, the hospitalization rate for community-acquired pneumonia is highest in children under 2 years of age, and the most common causative agents of pneumonia in this category of patients are respiratory viruses.