We first plotted the average weekly incidence rates over the time period studied and the median weekly incidence and mortality before and after IDSR implementation over the 23-week period of meningitis outbreaks.
The weekly incidence among troops in Kuwait had a similar bimodal distribution with significant increases during weeks 11 and 50.
The estimates of weekly incidence from these models can be potentially biased if the influence of epidemics is not taken into account.
Weekly incidence of self-reported respiratory infection among troops in Iraq fell into a bimodal distribution with increased rates during the end of January to April and the latter part of September to December, respectively.
Mean weekly incidence rates per 100,000 population for first and new episodes of ILI (ICD9 487) were calculated for "influenza virus active weeks" during each winter (weeks 40 to 20) as previously described [8].
For each outbreak, we calculated the time-to-peak of the outbreak as the number of weeks elapsed from the first alert threshold to the week with the maximum weekly incidence (i.e., the peak of the outbreak).
For each group, we examined the weekly incidence rates in relation to the WHO recommended alert threshold (5 cases per 100,000) and epidemic threshold (10 cases per 100,000) [29].
We then calculated the weekly incidence and mortality, expressed as cases and deaths per 100,000 inhabitants, by dividing the number of new cases and deaths occurring per week by the mean annual population of each reporting district.
The mean weekly incidence rates of ILI were compared for different age groups during these influenza seasons, together with 1999 2000 as an example of a winter season with a dominance of circulating influenza A H3N2 and high population morbidity (Figure 2), but where a new drift variant did not emerge.
The outcome variable was the weekly incidence of RCAP.
The overall mean weekly incidence of autochthonous DF was 0.04.
