Incidence of respiratory syncytial virus positivity in young Italian children referred to the emergency departments for lower respiratory tract infection over two consecutive epidemic seasons.

BACKGROUND: The rate and severity of respiratory syncytial virus (RSV) infections within the same nation may vary from one year to another. PATIENTS AND METHODS: The "Osservatorio VRS" study collected epidemiological data on RSV infection among Italian children aged < or = 4 years referred to emergency departments of 14 centers, for suspected lower respiratory tract infections (LRTI) in two consecutive RSV seasons (October 2000-April 2001 and October 2001-April 2002). Medical history and physical examination were recorded and an immunoenzymatic RSV test was performed on nasal secretions. Study variables were collected and evaluated separately, then compared.
RESULTS: In all, 272 and 756 children were included in the two seasons, respectively, of which 31.6% and 19.2% were RSV positive (+). Children of the first season had lower gestational and chronological age, higher rates of chronic lung disease (CLD), very low birth weight (< 1,500 g), larger use of corticosteroids or bronchodilators. Main risk factors for RSV infection were a young age (< 1 year) and a low birth weight (< 1,500 g). RSV infection reached its peak in February (first season) or March (second season), with an earlier appearance in the northern and central as compared to the southern regions. Rate of hospitalization and LRTI was higher in RSV+ children, especially if young.
CONCLUSION: Although rhythms of the RSV seasons and patient characteristics may vary from one year to another, the severity of RSV disease in nonprophylaxed infants and young children remains high.