Pneumoviridae

Pneumoviridae is a family of enveloped, negative-sense, single-stranded RNA viruses in the order Mononegavirales. It comprises two genera, Pneumovirus and Metapneumovirus, and includes several species that infect humans and animals. The most clinically important human pathogens are respiratory syncytial virus (RSV) and human metapneumovirus (HMPV).

The genus Pneumovirus includes RSV and bovine RSV; the genus Metapneumovirus includes HMPV and avian metapneumoviruses. The genome is nonsegmented, negative-sense RNA of about 15 kilobases, encoding proteins such as N, P, M, F, G, SH, M2, and L.

Virions are enveloped and pleomorphic with a helical nucleocapsid. Entry is via attachment by the G protein, followed by fusion mediated by the F protein. Transcription and replication occur in the cytoplasm; assembly and budding occur at the plasma membrane.

RSV and HMPV are major causes of acute respiratory infections, especially in young children. RSV is a leading cause of bronchiolitis and pneumonia in infants; HMPV causes similar illnesses across ages. Transmission occurs by respiratory droplets and close contact; seasonality is typical in winter in temperate regions.

Diagnosis relies on molecular assays such as RT-PCR. Treatment is supportive; antivirals are limited. Palivizumab provides RSV prophylaxis for high-risk infants, and nirsevimab has been approved for broader neonatal protection. Vaccines for RSV and HMPV are in development; none are widely licensed as of 2024.