Evolution and emergence of novel human infections

Arinaminpathy, N.; McLean, A. R.

Here we study the epidemiology associated with the establishment of a pathogen in a new host species. As discussed by Antia et al. (2003) even a pathogen poorly transmitted among humans, and thus capable only of causing sporadic cases, can acquire adaptations to become capable of sustained human transmission. Such adaptations could arise in response to the selective pressure exerted by the new host environment. Additionally, changing human contact patterns and environmental factors can have the same effect, of enhancing pathogen transmissibility (Woolhouse et al. 2005) . For example, the avian influenza subtype H5N1 has caused over 400 human cases (World Health Organization 2009), mostly through close contact with infected poultry (Beigel et al. 2005) . Although it has shown little or no transmission between humans, the possibility of its future adaptation to humans cannot be ruled out.