New and emerging diseases are a major health concern because we do not know much about them. We do not yet know how best to prevent and control them and, most importantly, we often do not know how to treat them, but it is likely that genetics and the state of the immune system of the global population plays a key role in disease prevalence [2] . With advances in medical treatment, greater numbers of disease-susceptible groups, such as immuno-compromised individuals are expected to survive longer in the overall population. This trend may change our understanding of pathogens because many unexpected microbes and infection pathways can appear within this transforming population.