Trend and seasonality of tuberculosis in Spain, 1996-2004.

This study aimed to analyse the trend and seasonality of tuberculosis (TB) in Spain over the past decade. Weekly TB incidence was calculated using data from the National Surveillance Network for the period 1996-2004. Secular trends and seasonal components were estimated using time-series analysis (least-squares method and Fourier transformation). A decline in incidence was observed, from 23.4 cases per 100,000 population in 1997 to 15.1 in 2004, and an annual cycle peaking in June was detected. Time-series analyses are necessary for detecting changes in the epidemiological pattern of TB in Spain, and it should be the first step towards the development of a predictive model.