Hospital-acquired adenovirus 7h infantile respiratory infection in Chile.

BACKGROUND: Adenoviruses are the second most common cause of viral acute lower respiratory tract infection (ALRI) requiring hospitalization in Chile. Little information is available with respect to nosocomial infection rate by adenovirus. This issue is important because of its potential severity and long term sequelae.
METHODS: Infants hospitalized for ALRI were studied to determine the rate of nosocomial cross-infection with respiratory adenovirus and its corresponding genome type. The group studied included all cases younger than 2 years of age admitted to a seven crib ward in the Roberto del Rio Children's Hospital (Santiago, Chile) between May, 1995, and October, 1996. Nasopharyngeal aspirates for immunofluorescence assay and viral isolation were obtained on admission and the next day. On identification of a positive case for adenovirus, samples were obtained from contacts for 2 consecutive days and twice weekly thereafter for 2 weeks.
RESULTS: Fifteen index positive cases for adenovirus and their 65 contacts were identified. Secondary attack rate for adenoviral cross-infection was 55%, most of which were diagnosed by viral isolation. Mortality occurred in 4 cases; 3 had underlying diseases. Four secondary cases presented mild respiratory infection after acquiring the cross-infection, and 16 patients developed a moderate and severe ALRI. Twelve patients required supplemental oxygen and 4 needed mechanical respiratory support. Genome types for the 10 index cases and 19 contacts were obtained. All of these corresponded to adenovirus 7h.
CONCLUSIONS: The high secondary attack rate observed, stresses the importance of adequate isolation of patients and the need for rapid and sensitive viral diagnosis.