Respiratory syncytial virus infections in adults: a narrative review

Respiratory syncytial virus (RSV), an RNA virus spread by droplet infection that affects all ages, is increasingly recognised as an important pathogen in adults, especially among older people living with comorbidities. Distinguishing RSV from other acute viral infections on clinical grounds alone, with sufficient precision to be clinically useful, is not possible. The reference standard diagnosis is by PCR: point-of-care tests perform less well with lower viral loads. Testing samples from a single respiratory tract site could result in underdetection. RSV is identified in 6-11% of outpatient respiratory tract infection (RTI) consultations in older adults (≥60 years, or ≥65 years, depending on the study) and accounts for 4-11% of adults (≥18 years) hospitalised with RTI, with 6-15% of those hospitalised admitted to intensive care, and 1-12% of all adults hospitalised with RSV respiratory tract infection dying. Community-based studies estimate the yearly incidence of RSV infection at around 3-7% in adults aged 60 years and older in high-income countries. Although RSV accounts for a similar disease burden as influenza in adults, those hospitalised with severe RSV disease are typically older (most ≥60 years) and have more comorbidities, more respiratory symptoms, and are frequently without fever. Long-term sequelae are common and include deterioration of underlying disease (typically heart failure and COPD). There are few evidence-based RSV-specific treatments currently available, with supportive care being the main modality. Two protein subunit vaccines for protection from severe RSV in adults aged 60 years and older were licensed in 2023, and a third-an mRNA-based vaccine-recently gained market approval in the USA. The phase 3 studies in these three vaccines showed good protection against severe disease. Data on real-world vaccine effectiveness in older adults, including subgroups at high risk for RSV-associated hospitalisation, are needed to establish the best use of these newly approved RSV vaccines. New diagnostics and therapeutics are being developed, which will also need rigorous evaluation within their target populations to ensure they are used only for those in whom there is evidence of improved outcomes. There is an urgent need to reconceptualise this illness from one that is serious in children, but far less important than influenza in older people, to thinking of RSV as also a major risk to health for older people that needs targeted prevention and treatment.