Respiratory syncytial virus and metapneumovirus in children over two seasons with a high incidence of respiratory infections in Brazil.

Acute respiratory infections (ARI) are one of the most important causes of death in children. Human metapneumovirus (HMPV), a virus first described in 2001, has now been detected in almost all continents. HMPV causes bronchiolitis and pneumonia with a clinical spectrum similar to respiratory syncytial virus (RSV). We describe the incidence of HMPV and RSV during two consecutive seasons with a high incidence of ARI in Aracaju, Brazil. HMPV was responsible for 24% of cases of bronchiolitis in the 1st season (April-May 2002) but was not found in the 2nd year (April-May 2003). RSV was recovered from 61 (55%) children with ARI in 2002 and from 72 (68%) in 2003. Children with RSV bronchiolitis in 2002 had more hypoxia but less wheezing than in 2003. The incidence of HMPV and RSV genotypes causing bronchiolitis varied between the years. Long-term prospective studies are required to better describe the epidemiology of these viruses in children.