In research published in the Proceedings of the Royal Society of London B, a team led by Rob Dunn of North Carolina State University looked for correlations among a number of different factors, including population, disease control, human history, the prevalence of pathogens, and several climatic and geographical variables.

They found that the strongest correlation with pathogen number was actually the diversity of birds and mammals. However, the researchers suggest that rather than being a causal factor, animal diversity is simply a proxy for climate – the environmental factors that have influenced patterns of bird and mammal diversity have done the same for disease diversity.

The actual abundance of the pathogens is determined less by the environment than by health-care spending. ‘On the one hand, we are not very effective at altering the numbers of kinds of pathogens present, as those numbers are strongly correlated with environmental conditions,’ Dunn said. ‘But on the other hand, we can control
the prevalence of pathogens by spending money on disease-control efforts. It is the prevalence that influences human health and well being.’

June 2010