Trends of severe human metapneumovirus infections in India

BACKGROUND: In December 2024 and early January 2025, China reported increased acute respiratory infections with increased detections of seasonal influenza, rhinovirus, RSV and hMPV during the Northern Hemisphere winter. We strengthened hMPV surveillance through the existing pan-India surveillance network for acute respiratory illness (ARI) and severe acute respiratory infection (SARI). METHODOLOGY: To rapidly generate nationwide situational data without overburdening laboratories already performing routine respiratory virus surveillance, each site was asked to test up to five eligible SARI samples per week for hMPV from January to April 2025. Eligible samples were hospitalized SARI cases that were negative for influenza, SARS-CoV-2 and/or RSV, as applicable to age-based testing algorithms, across 70 laboratories. RESULTS: Of 8,246 enrolled SARI cases, 4,149 eligible samples were tested for hMPV under the capped weekly sampling strategy, and 59 were positive (1.42%; 95% CI: 1.10-1.83). Positivity ranged from 0.5% to 2.9% across age groups and was highest in children aged <2 years. Most patients (63%) were aged <2 years. Positivity was higher among males (1.7% vs 1.1% in females), and was highest in January (2.1%) before declining to 0.5% in April. The most common symptoms were cough (95%), fever (88%), and breathlessness (58%). Outcomes were available for 54/59 patients: 11 required ICU admission, 51 were discharged alive, and 3 died. Among seven patients with comorbidities, all were discharged alive. More than half of the sequenced viruses belonged to clade B1, followed by B2 and A2b2. CONCLUSION: In this limited sentinel surveillance of severe respiratory infections, hMPV was detected infrequently but was observed predominantly among young children. Continued multi-season surveillance is needed to better define age-specific burden, temporal patterns, and circulating genotypes in India. CLINICAL TRIAL NUMBER: Not applicable.