1. Methods to assess seasonal effects in epidemiological studies of infectious diseases— exemplified by application to the occurrence of meningococcal disease 
C.F. Christiansen, L. Pedersen, H.T. Sørensen, K.J. Rothman 
Clinical Microbiology and Infection 
Volume 18, Issue 10, Pages (October 2012)
DOI: /j x
Copyright © 2012 European Society of Clinical Infectious Diseases Terms and Conditions

2. FIG. 1.
The terminology of seasonal variation exemplified by a simple sine curve.
Clinical Microbiology and Infection  , DOI: ( /j x)
Copyright © 2012 European Society of Clinical Infectious Diseases Terms and Conditions

3. FIG. 2.
Example of monthly counts of meningococcal disease weighted by the length of the month (black dots) and fitted to a sine curve (red line/linear model) and to a log-linear Poisson model (blue dashed line/log-linear model).
Clinical Microbiology and Infection  , DOI: ( /j x)
Copyright © 2012 European Society of Clinical Infectious Diseases Terms and Conditions