Journal of Medical Virology 65:408±412 (2001) Occurrence and Severity of Infections Caused by Subgroup A and B Respiratory Syncytial Virus in Children in Southeast Brazil O.A.L. Cintra, 1 * M.A. Owa, 2 A.A. Machado, 2 M.C. Cervi, 1 L.T.M. Figueiredo, 2 G.M. Rocha, 1 M.M. Siqueira, 4 and E. Arruda 3 1 Department of Pediatrics, University of SaÄo Paulo School of Medicine at RibeiraÄo Preto, RibeiraÄo Preto, SaÄoPaulo, Brazil 2 Department of Internal Medicine, University of SaÄo Paulo School of Medicine at RibeiraÄo Preto, RibeiraÄo Preto, SaÄoPaulo, Brazil 3 Department of Cell Biology and Microbiology, University of SaÄo Paulo School of Medicine at RibeiraÄo Preto, RibeiraÄoPreto, SaÄo Paulo, Brazil 4 Virology Section, Oswaldo Cruz Institute, Rio de Janeiro, RJ, Brazil The frequency and severity of infections caused by respiratory syncytial virus (RSV) were asses- sed in children <2 years of age seen at the emer- gency department. The frequency of RSV detection in the clinical virology laboratory dur- ing the past 3 years was also analyzed retro- spectively. RSV was found in 21.6% (188/869) of the samples collected from children seen at the emergency department and was found to be more frequent during the autumn, being less frequent or negligible by midwinter. RSV subgroups A and B co-circulated within the same time period in children seen at the emergency department, with varying predominance of either subgroup. There was no signi®cant association of RSV subgroup with disease severity, but only a trend for RSV subgroup B being more frequent in children with risk factors for severe disease. J. Med. Virol. 65:408±412, 2001. ß 2001 Wiley-Liss, Inc. KEY WORDS: respiratory syncytial virus; acute respiratory infections; bronchiolitis INTRODUCTION Respiratory syncytial virus (RSV) is the single most important agent of acute lower respiratory infections in young children worldwide and causes major annual winter outbreaks with consequent increases in hospi- talization and death among youngsters in temperate regions of the world [Gilchrist et al., 1994]. In these regions, the two known RSV subgroups (A and B) co- circulate during epidemic seasons with variable pre- dominance of one relative to the other [Anderson et al., 1985; Monto and Ohmit. 1986]. Studies carried out in the Northern Hemisphere have shown that both RSV groups cause illnesses that are indistinguishable on the basis of clinical and epidemiological characteristics [La Via et al., 1992]. Seasonality of RSV is generally less clear-cut in tropical areas of the world [Weber et al., 1998]. A 32-month prospective study is reported on the occurrence of RSV subgroups A and B in children with acute respiratory infection who sought medical care at the University of Sa Ä o Paulo Hospital, a tertiary care facility located in the city of Ribeira Äo Preto, state of Sa Äo Paulo, Brazil. In order to document further RSV seasonality in this region, the frequency of RSV de- tection in samples submitted to the clinical virology laboratory was analyzed. These samples were collected from children with acute respiratory infection seen at the emergency department as outpatients, or admitted as inpatients in the last 3 years. PATIENTS AND METHODS Prospective Emergency Department Study The study enrolled children under 2 years of age seen at the pediatric emergency department of the Uni- versity of Sa Äo Paulo Hospital, in the city of Ribeira Äo Preto, state of Sa Ä o Paulo, southeastern Brazil, with ARI of duration shorter than 7 days, from May 1993 to December 1995. The exclusion criteria were age over 2 years and duration of respiratory symptoms longer Grant sponsor: State of Sa Äo Paulo Research Foundation (FAPESP). *Correspondence to: O.A.L. Cintra, Department of Paediatrics, University of Sa Äo Paulo School of Medicine at Ribeira Äo Preto, Av. Bandeirantes, 3900-CEP, 14051-970 Ribeira Ä o Preto, SP, Brazil. E-mail: oacintra@keynet.com.br Accepted 9 March 2001 ß 2001 WILEY-LISS, INC.