Background: The Spanish daily mortality monitoring system and the program «European monitoring of excess mortality for public health action» found two excesses of mortality in Spain in November and December 2009.
Methods: We analyzed the evolution of mortality in Spain during those months using time-series analysis methods based on historical mortality series and compared it in the time with influenza transmission.
Results: Observed mortality for the total population was higher than expected in two periods: weeks 46-47/2009 with 5.75% excess and weeks 51-52/2009 with 7.35% excess. Observed mortality higher than expected, was also observed in children 5-14 years old during weeks 46-48/2009 with 41 deaths vs 21 expected. Exces mortality in November occurred before or was concomitant with highest influenza incidence rates. Excess mortality in December occurred five weeks after the influenza incidence peak and along with dramatic drop in temperatures. RSV and traffic accidents were ruled out as factor associated to these excesses.
Conclusions: While temperatures could explain most of the excess mortality observed in December, no single factor could be associated with observed excess mortality in November.