Henipaviruses — unanswered questions of lethal zoonoses

The highly lethal Hendra and Nipah viruses have been described for little more than a decade, yet within that time have been aetiologically associated with major livestock and human health impacts, albeit on a limited scale. Do these emerging pathogens pose a broader threat, or are they inconsequential ‘viral chatter’. Given their lethality, and the evident multi-generational human-to-human transmission associated with Nipah virus in Bangladesh, it seems prudent to apply the precautionary principle. While much is known of their clinical, pathogenic and epidemiologic features in livestock species and humans, a number of fundamental questions regarding the relationship between the viruses, their natural fruit-bat host and the environment remain unanswered. In this paper, we pose and probe these questions in context, and offer perspectives based primarily on our experience with Hendra virus in Australia, augmented with Nipah virus parallels.

► Hendra virus was first identified in 1994 in horse in Australia with 32 spillover events by 2011. ► Nipah virus was first identified in 1999 in pigs in Malaysia and later in Singapore, India and Bangladesh. ► Questions remain about the relationship among the viruses, fruit-bat host and environment. ► Disease emergence is ecological process. Challenge is to identify drivers and counter them.