Negative binomial regression seasonal occurrence models.

IRR = incidence rate ratio, calculated by exponentiating regression coefficient. *: The IRR for the Equatorial group exceeds 1 despite the lower total frequency of cases among these countries (Fig 2a). This arises because, due to the large number of cases in equatorial Indonesia, the estimated rate of case occurrence is higher among Equatorial countries. However, because there were only three Equatorial countries, the total case frequency remains lower than in the more numerous Northern-hemisphere countries. Negative binomial regression seasonal occurrence models.