Infectious diseases continue to impose unpredictable burdens on global health and economies, a subject that requires constant research and updates. In this sense, the objective of the present article was to review studies on the role of wild animals as reservoirs and/or dispersers of etiological agents of human infectious diseases in order to compile data on the main wild animals and etiological agents involved in zoonotic outbreaks. A systematic review was carried out using PRISMA guidelines, using the PubMed, Scopus and SciELO platforms as data banks. The descriptors used were 'zoonosis', 'human infectious diseases' and 'wild animals'. The results show that wild animals (mainly bats, birds and primates) play an important role in the dissemination of etiological agents (mainly viruses, as a new coronavirus called 2019 Novel Coronavirus) in extensive geographic regions. Moreover, these wild animal organisms can act as the site for essential biotic synergy among several pathogenic microorganisms, promoting a higher rate of adaptation, mutation and even genetic recombination, with consequent stimulation of new strains and subtypes, inducing new infectious agents with unknown virulent potential. In conclusion, the monitoring of these diseases and adequate preparation for possible epidemics and pandemics are fundamental conditions for the mitigation of their future impact. The zoonotic threat of these etiological agents and the impact on public health can be enormous as shown by the ongoing epidemic of 2019 novel coronavirus (2019- nCoV) infections.

Yellow fever is an acute viral disease endemic to tropical countries, like Brazil, where, since the 1940s, has no significant documented outbreaks similar to that observed between 2016/2018 (2 045 confirmed cases and 677 deaths; caused by the sylvatic form). The principal manipulating factors inciting this change were absence of appropriate vaccination campaigns and increased urbanization & population growth in forest areas, with prevalence of the virus in the species inhabiting of these areas. The 2016/2018 outbreaks exhibited incidence in areas with historically low or no yellow fever virus activity, triggering a surge in recorded deaths - mainly in the Southeastern states of Brazil. The Brazilian government aggressively responded, reforming the countries' prophylactic measures, including vaccine implementation - as of March, 2018, switching from the former double dose regimen of the vaccine, to a single dose protocol, deemed as adequate. Moreover, some states appropriated the fractionated dosage (1/5 of the standard dose), in foresight of potential vaccine shortages. To prevent the uprising of new sylvatic yellow fever cases in Brazil, it's obligatory the development of effective combative plans, including adaptation of prophylactic measures individually (use of repellents, protective clothing etc.), applicable vaccination campaigns in every endemic region, to raise awareness to locals and visitors alike. Notwithstanding these preventative strategies, the persistence of cases and the recent outbreaks in Brazil, highlight the possible ineffectiveness of combative measures. Based on these considerations, the objective of this review was to raise more awareness of the epidemiological impact of the disease in Brazil.