Epidemiology of human metapneumovirus among children with severe or very severe pneumonia in high pneumonia burden settings: the PERCH study experience.

Objectives: After respiratory syncytial virus (RSV), human metapneumovirus (hMPV) was the second-ranked pathogen attributed to severe pneumonia in the PERCH study. We sought to characterize hMPV-positive cases in high burden settings, which have limited data, by comparing to RSV-positive and other cases.

Methods: Children aged 1-59 months hospitalized with suspected severe pneumonia and age/season-matched community controls in seven African and Asian countries had nasopharyngeal/oropharyngeal swabs tested by multiplex PCR for 32 respiratory pathogens, among other clinical and lab assessments at admission. Odds ratios adjusted for age and site (aOR) were calculated using logistic regression. Etiologic probability was estimated using Bayesian nested partial latent class analysis. Latent class analysis identified syndromic constellations of clinical characteristics.

Results: HMPV was detected more frequently among cases (267/3887, 6.9%) than controls (115/4976, 2.3%), among cases with pneumonia chest X-ray findings (8.5%) than without (5.5%), and among controls with respiratory tract illness (3.8%) than without (1.8%; all p≤0.001). HMPV-positive cases were negatively associated with the detection of other viruses (aOR=0.18), especially RSV (aOR=0.11; all p<0.0001), and positively associated with the detection of bacteria (aORs 1.77, p=0.03). No single clinical syndrome distinguished hMPV-positive from other cases. Among hMPV-positive cases, 65.2% were aged <1 year and 27.5% had pneumonia danger signs; positive predictive value was 74.5%; mortality was 3.9%, similar to RSV-positive (2.4%) and lower than other cases (9.6%).

Conclusions: HMPV-associated severe pediatric pneumonia in high burden settings was predominantly in young infants and clinically indistinguishable from RSV. HMPV-positives had low case fatality, similar to that in RSV-positives.