Modelling seasonality and viral mutation to predict the course of an influenza pandemic.

As the 2009 H1N1 influenza pandemic (H1N1) has shown, public health decision-makers may have to predict the subsequent course and severity of a pandemic. We developed an agent-based simulation model and used data from the state of Georgia to explore the influence of viral mutation and seasonal effects on the course of an influenza pandemic. We showed that when a pandemic begins in April certain conditions can lead to a second wave in autumn (e.g. the degree of seasonality exceeding 0.30, or the daily rate of immunity loss exceeding 1% per day). Moreover, certain combinations of seasonality and mutation variables reproduced three-wave epidemic curves. Our results may offer insights to public health officials on how to predict the subsequent course of an epidemic or pandemic based on early and emerging viral and epidemic characteristics and what data may be important to gather.

New coronal caries in older adults: implications for prevention.

To characterize the extent and severity of coronal caries among older US adults and document their need for prevention interventions, we systematically reviewed studies on coronal caries incidence, increment, and attack rate. We abstracted six studies and calculated summary measures using a random-effects model (95% confidence interval [95%CI]). We tested for heterogeneity and identified associated factors by examining the correlation between outcome measures and baseline population risk and study characteristics. We re-calculated summary measures after adjusting outcomes that netted out examiner reversals. Incidence and increment varied significantly by study. Adjusting studies for netting out examiner reversals reduced heterogeneity significantly. Annual attack rate among adjusted North American studies was 1.4 surfaces per 100 surfaces (95%CI = 1.0-1.9), or approximately 1 new carious surface per person per year. These rates are equal to or higher than those in children and indicate a need for caries-prevention services.

Estimating rates of new root caries in older adults.

Although older adults are keeping their teeth longer, no national data are available on new caries in this age group. To characterize the extent of caries among older adults, we systematically reviewed studies on root caries incidence, increment, attack rate, and annual total (root + coronal) caries increment. We used a random-effects model to estimate annual summary measures and their 95% confidence intervals (CI) and tested for heterogeneity. For the 9 studies reporting root caries incidence, the summary measure equaled 23.7% (CI = 17.1-30.2%). For the 9 studies reporting root caries increment, the summary measure was 0.47 surfaces (CI = 0.34-0.61). For the 7 studies reporting total caries increment, the summary measure equaled 1.31 surfaces (95% CI = 1.01-1.61 surfaces). Because of heterogeneity, summary measures should be interpreted with caution. This research suggests, however, that older adults experience high rates of new caries and could benefit from caries-prevention programs.