Effect of population characteristics and seasonal variation on anthrax epidemiology

Abstract: Introduction Anthrax is a disease caused by the spores of Bacillus anthracis and can have a high fatality rate. It is a zoonosis and mostly affecting animals. In this study I want to find out risk factors on population scale for anthrax cases and deaths in humans and animals, and look at the relation of anthrax with weather patterns. Methods I searched for anthrax outbreaks in different countries, mainly yearly reports. I looked at human cases, human deaths, livestock deaths and wildlife deaths. Different risk factors were considered: country size, population characteristics, Human Development Index (HDI), total cattle number, cattle per human ratio, mean annual temperature, mean temperature of the warmest 1 and 3 months, annual precipitation and minimum and maximum precipitation in 1 month and 3 months. Linear regression was used. Statistics were repeated without China because it was often the single outlier in the figures. Statistics were also repeated with the countries aggregated in continents because of the modifiable area unit problem. Results Data was found for 28 countries resulting in 36 data points. There was a significant relation between human cases and cattle number, human deaths, country size and population size. There were also significant relations between wildlife deaths and population size, country size and mean temperature of the warmest month. Without China relations between human cases and maximum precipitation in 1 and 3 months, and between livestock deaths and country size were significant. For continents a significant relation between human cases and cattle ratio, cattle deaths and HDI. Conclusion This study mainly shows that high cattle numbers and cattle deaths due to anthrax are risk factors for human cases. Also seasonal precipitation is a risk factor. Bigger country size and population size may be indirect risk factors as these usually accompany higher cattle numbers.