Vírus respiratório sincicial em lactentes internados com infecção aguda do trato respiratório inferior

Abstract

Resumo: 0 virus respiratorio sincicial (VRS) e considerado o mais importante patogeno virai na infeccao respiratoria aguda (IRA), principalmente em lactentes menores de dois anos. Infeccoes por VRS ocorrem em surtos sazonais, com pico de incidencia nos meses frios, associadas a um aumento significante das hospitalizacoes por IRA. Criancas com fatores de risco, como prematuridade, cardiopatias congenitas, doencas pulmonares cronicas, imunodeficiencias e idade inferior a seis semanas de vida, apresentam risco maior de hospitalizacao, morbidade e mortalidade por VRS. Os objetivos foram: 1)verificar a prevalencia da infeccao por VRS em lactentes menores de dois anos, com infeccao aguda do trato respiratorio inferior, hospitalizados nas Enfermarias Pediatricas do Hospital de Clinicas da Universidade Federal do Parana; 2) comparar as caracteristicas clinicas, laboratoriais e evolutivas nos pacientes com e sem infeccao por VRS e 3) comparar estas caracteristicas nos pacientes VRS positivos com e sem fatores de risco. A identificacao de virus respiratorios foi realizada por tecnica de imunofluorescencia indireta em aspirado de nasofaringe. Dos 112 pacientes estudados, de abril a agosto de 1997, 46 (41,1%) apresentaram infeccao por VRS. Nos meses de estudo, este agente foi identificado em 46,2%, 50,0%, 38,7% e 50,0% das amostras coletadas em abril, maio, junho e julho, respectivamente. Nenhum caso foi identificado no mes de agosto. Os pacientes VRS positivos eram significativamente mais jovens que os VRS negativos, com 87% das criancas menores de um ano e 71,7% menores de 6 meses. Os sinais e sintomas na admissao, bem como o manejo terapeutico foram semelhantes nos pacientes VRS positivos e negativos. No raio X de torax, uma maior prevalencia de hiperinsuflacao (p=0,0009) e da associacao de hiperinsuflacao e infiltrado peribronquico perihilar bilateral (p=0,003) foram encontradas nos pacientes com VRS. Estes pacientes tinham hemograma com percentual maior de linfocitos, enquanto os pacientes VRS negativos apresentaram maior contagem de leucocitos e neutrofilos. O VRS foi responsavel por 71,4% das bronquiolites, 33,3% das broncopneumonias e 45% das traqueobronquites. A evolucao clinica nos dois grupos foi semelhante. Entre os pacientes VRS positivos, 45,7% apresentavam um ou mais fatores de risco para doenca grave por VRS. As caracteristicas clinicas dos pacientes VRS positivos com e sem fatores de risco foram similares, exceto pela presenca de sibilancia, que foi mais frequente no grupo sem fatores de risco (p=0,03). Criancas com fatores de risco apresentaram maior gravidade, com maior frequencia de casos de apneia, necessidade de ventilacao mecanica e tempo de permanencia em Unidade de Terapia Intensiva. Demonstrouse que em Curitiba, o VRS e um importante patogeno na infeccao do trato respiratorio inferior em criancas. O periodo estudado provavelmente correspondeu a um surto de VRS na comunidade. Os pacientes infectados pelo VRS com fatores de risco apresentaram maior gravidade de doenca do que os sem fatores de risco.

Abstract: Respiratory syncytial virus (RSV) is the most important viral pathogen of acute respiratory infections (ARI), especially in infants younger than two years of age. RSV infection occurs in seasonal outbreaks with a peak incidence in cold months, and are attributed to a significant increase in the number of children hospitalized with ARI. Infants and children at highest risk for hospitalization, morbidity and mortality due to RSV are those with congenital heart disease, prematurity, chronic lung disease, immunosupression and infants less than six weeks of age. The aims of this study were: 1) to assess the prevalence of RSV infections in infants under two years of age with acute lower respiratory infection, hospitalized in the pediatric wards of the Hospital de Clinicas of the Federal University of Parana State; 2) to compare clinical and laboratory findings and patient's outcome between those with and without RSV infection; 3) and to compare the clinical findings of patients having RSV infection with and without risk factors. Respiratory viruses were identified by indirect immunofluorescence assay of nasal secretion. Of 112 patients observed from April to August 1997, 46 (41,1%) had RSV infection confirmed. During the study periods of April, May, June and July, RSV was identified in 46,2%, 50,0%, 38,7% and 50,0% of patients tested, respectively. In August, no case of RSV was identified. Patients with RSV were considerably younger than patients without RSV, with 87% of them being less than twelve months old, and 71,7% less than 6 months of age. The clinical findings on admission as well as their management were similar in patients who had RSV infection and those who did not. On X-ray examination, a high prevalence of air trapping (p=0,0009) and a high association of air trapping and peribronchial thickening (p=0,003) were found in the patients with RSV. The white blood count differed between the patients with and without RSV infection: a high percentage of lymphocytes was found in the RSV group, and a high number of leucocyte and neutrophyl count was found in the non-RSV group. RSV was responsible for 71,4% of bronchiolitis, 33,3% of pneumonias and 45% of bronchitis. The clinical evolution in both patient groups was similar. Amongst patients positive for RSV infection, 45,7% presented one or more risk factors for severe forms of RSV infection. The clinical findings were similar in patients positive for RSV infection with and without risk factors, except for the presence of wheezing, which was more frequent in the group of patients without risk factors (p=0,03). Children with risk factors presented more severe clinical forms, with a greater prevalence of apnea, need for mechanical ventilation, and time spent in the Intensive Care Unit. This study demonstrated that RSV is an important pathogen of lower respiratory tract infection in children. The study period most likely coincided with a seasonal outbreak of RSV infection. Patients infected by RSV with risk factors presented more severe clinical forms of RSV infection than those without risk factors.