Researchers of the Pneumonia Etiology Research for Child Health (PERCH) study reported that viruses are the leading cause of severe pneumonia in children younger than five years without human immunodeficiency virus (HIV) infection.1 Of the 61% of viral causes, respiratory syncytial virus (RSV) was the biggest culprit – accounting for one-third of all cases.1 Meanwhile, bacteria accounted for only 27% of severe childhood pneumonia requiring hospitalisation.1
Pneumonia remains the greatest cause of death in children younger than five years old worldwide, accounting for 16% of all deaths in 2015.2 Pneumonia can affect children everywhere but is most prevalent in South Asia and sub-Saharan Africa. Empirical antibiotic treatment and effective vaccines against bacterial pathogens have been made available in efforts to reduce pneumonia mortality.1 However, the progress is largely hindered by the absence of interventions (e.g., vaccination) against the remaining common pathogens, in particular viruses.
A total of 4,232 hospitalised children with severe pneumonia from Bangladesh, The Gambia, Kenya, Mali, South Africa, Thailand, and Zambia were enrolled into the PERCH study.1 Over two years, researchers collected and analysed nose and throat swabs, urine, blood, sputum, and other fluid samples. The study aimed to characterise the causes of severe childhood pneumonia requiring hospital admission in low-income and low-middle-income settings with routine pneumococcal, pertussis, Haemophilus influenzae type b (Hib), and measles vaccines.
Previous studies have also identified RSV as the dominant pathogen in childhood pneumonia. This includes the multisite Board of Science and Technology for International Development (BOSTID) study which detected RSV more frequently than bacteria in children with pneumonia.3 The multicountry Global Approach to Biological Research, Infectious Diseases and Epidemics in Low-income countries (GABRIEL) study also reported Streptococcus pneumoniae, RSV, and rhinovirus as major pathogens associated with pneumonia in children under five years of age.4 In the Centers for Disease Control and Prevention (CDC) Etiology of Pneumonia in the Community (EPIC) study, RSV was more commonly detected among children with pneumonia younger than five years of age than among older children.5
The PERCH study recorded a prevalence of less than 5% of influenza A or B; 2% to 30% of human rhinovirus; 3% of S. pneumoniae; and 6% to 10% of Mycobacterium tuberculosis.1 Bordetella pertussis was most commonly found in children younger than 12 months but otherwise rarely identified while Hib was less common than non-type b H. influenzae. Pneumocystis jirovecii was also detected in malnourished children younger than six months, and was more prominent in those with HIV infection.
The findings of the PERCH study emphasise that beyond urgent intervention targeting RSV in severe childhood pneumonia with hospitalisation, it is also crucial to identify children for whom antibiotics are unlikely to be of benefit – to prevent antibiotic resistance.