Nipah Virus Disease: Epidemiological, Clinical, Diagnostic and Legislative Aspects of This Unpredictable Emerging Zoonosis

SIMPLE SUMMARY: This review summarizes fundamental aspects of Nipah virus (NiV) infection with particular emphasis on disease in swine and its zoonotic potential, focusing on epidemiology, clinical signs, diagnosis, prevention and legislation. The main outbreaks were reported in Southeast Asia, and, in humans and pigs, a severe disease can be characterized by respiratory and neurological signs, and high mortality. This viral infection has, like other recent infections, a natural reservoir in bats, but human-to-human transmission has been also recorded. Effective treatments and prophylaxis are still main goals due to the still scarce knowledge on the infection in humans with regards to the pathogenetic- and immunological-related features of the disease. The effects of climate change should be considered together with the anthropogenic pressure on ecosystems where zoonoses can spread. Action and surveillance plans should be continuously employed to monitor areas at risk as, as today they represent an essential preventive measure to avoid the onset and diffusion of outbreaks, even in countries that have direct/indirect relationships with countries at risk. ABSTRACT: Nipah virus (NiV) infection is a viral disease caused by a Henipavirus, belonging to the Paramyxoviridae family, responsible for a zoonosis. The course of the disease can be very serious and lead to death. NiV natural hosts are fruit bats (also known as megabats) belonging to the Pteropodidae family, especially those of the Pteropus genus. Natural infection in domestic animals has been described in farming pigs, horses, domestic and feral dogs and cats. Natural NiV transmission is possible intra-species (pig-to-pig, human-to-human) and inter-species (flying bat-to-human, pig-to-human, horse-to-human). The infection can be spread by humans or animals in different ways. It is peculiar how the viral transmission modes among different hosts also change depending on the geographical area for different reasons, including different breeding methods, eating habits and the recently identified genetic traits/molecular features of main virus proteins related to virulence. Outbreaks have been described in Malaysia, Singapore, Bangladesh, India and the Philippines with, in some cases, severe respiratory and neurological disease and high mortality in both humans and pigs. Diagnosis can be made using different methods including serological, molecular, virological and immunohistochemical methods. The cornerstones for control of the disease are biosecurity (via the correct management of reservoir and intermediate/amplifying hosts) and potential vaccines which are still under development. However, the evaluation of the potential influence of climate and anthropogenic changes on the NiV reservoir bats and their habitat as well as on disease spread and inter-specific infections is of great importance. Bats, as natural reservoirs of the virus, are responsible for the viral spread and, therefore, for the outbreaks of the disease in humans and animals. Due to the worldwide distribution of bats, potential new reports and spillovers are not to be dismissed in the future.