Infants with both respiratory syncytial virus and metapneumovirus are more apt to develop bronchiolitis?severe inflammation of the small airways of the lung. The study involved children under 2 years of age who were hospitalized during the winter of 2001-2002. The researchers based their findings on a comparison of the rates of dual infection with both viruses among children who were moderately ill and were admitted to general pediatric wards, versus those with severe disease who required a respirator in the intensive care unit. Dual infection, the researchers discovered, produced a 10-fold higher risk of needing intensive care unit mechanical ventilation.