Respiratory syncytial virus epidemic periods in an equatorial city of Brazil.

BACKGROUND: Characterization of the human respiratory syncytial virus (HRSV) season at the local level has important implications for appropriate decisions on the time period for administration of specific prophylaxis. OBJECTIVES: (1) To describe five consecutive epidemic periods of HRSV in an equatorial city of Brazil and (2) to show preliminary data on genomic diversity of circulating HRSV. PATIENTS/METHODS: Nasopharyngeal aspirates of 2885 children attending the emergency room and wards of a public hospital were collected and screened by indirect immunofluorescence for HRSV infections during five consecutive years (from January 2004 to December 2008). In addition, the genetic and antigenic variability of the HRSV strains isolated was evaluated by partial nucleotide sequencing of the protein G gene. RESULTS: HRSV was detected in 15·8% of the analyzed samples. HRSV seasons occurred in a restricted period of each year. The onset of each HRSV season was variable (February to May), but the end always occurred in July. From the 456 HRSV infections found, 86 cases with bronchiolitis were genotyped. Both HRSV subgroups (A and B) cocirculated during the five epidemic periods. The 58 HRSV-A strains grouped into two clades, GA2 and GA5. In respect of the HRSV-B strains, the 28 samples grouped into two clades: GB3 and BA. CONCLUSIONS: HRSV accounts for a substantial proportion of ARI in the study population. As in temperate countries, HRSV infections in this equatorial area of Brazil also cause seasonal yearly epidemics, and this has implications for prophylaxis strategies. The city of Fortaleza follows the same worldwide trend of circulation of genotypes of HRSV.

Comparative dynamics, morbidity and mortality burden of pediatric viral respiratory infections in an equatorial city.

BACKGROUND: Although acute respiratory infections (ARIs) are the global leading cause of pediatric morbidity and mortality, the relative impact of viral pathogens on pediatric ARIs is still poorly understood, especially in equatorial settings. Long-term studies of multiple viruses concurrently circulating in these regions are still lacking. Here, we report the results of a systematic prospective surveillance of multiple respiratory viruses conducted every weekday for nearly a decade in an equatorial city in Brazil. METHODS: We analyzed the relative burden of influenza, parainfluenza, respiratory syncytial virus (RSV), adenovirus, and metapneumovirus, their seasonality, and their association with climatic and demographic factors, ARI diagnosis, and pediatric mortality. RESULTS AND CONCLUSIONS: RSV was the primary driver of severe childhood respiratory infections, including pneumonia. RSV was also the virus most strongly associated with respiratory-associated deaths, with RSV circulation and pediatric mortality being in phase. Annual circulation of influenza peaked much earlier than annual mortality due to respiratory causes. The results also show that viral circulation can be strongly seasonal even in equatorial regions, which lack seasons with low temperatures: RSV and influenza were concentrated in the rainy season, whereas parainfluenza predominantly circulated in the dry season. The consistent epidemiologic patterns observed can be used for an effective adjustment of the timing of therapeutic and prophylactic interventions in this and potentially in other equatorial regions.