Respiratory syncytial virus seasonality in Brazil: implications for the immunisation policy for at-risk populations

Freitas, André Ricardo Ribas; Donalisio, Maria Rita

The same annual cycle pattern with a small peak appearing after 6 months can also be observed in Fig. 2 , corresponding to the hospitalisation rates for bronchiolitis and pneumonia. These stable annual activity patterns identified using wavelets allow the analysis by means of Fourier decomposition of the complete time series for years 2005-2012. RSV seasonality analysis through Fourier decomposition of the time series assay results allowed identifying regional differences between the greater activity periods in the distinct regions of Brazil. The RSV peak occurred in the North and Midwest regions in the second week of April (peak = 4.4), in the Northeast in the first week of May (peak = 5.1), in the Southeast in the beginning of April, and in the South in the first week of June (peak = 6.2; Table II ). The seasonality Fourier decomposition analysis of the monthly rates of hospitalisation for RSV-associated bronchiolitis and pneumonia showed similar results when compared with the results from the positivity series of assays in the same region (Table II) . In general, the criteria are mutually consistent, with matching results.