[Differentiation, emergence and re-emergence of viral pathogens: past, present, future].

Viruses and viral diseases have been the subject of interest for science and some of our greatest challenges and achievements are in the field of virology. Cases of emerging and re-emerging infections have posed problems and sometimes enormous public health challenges. Despite significant advances in understanding pathogen biology, the molecular mechanisms of pathogenesis, breakthroughs in the prevention of these infections, and their impact on public health and the global economy, the emergence of new pandemic viruses remains unclear. This review article presents the current state of knowledge on newly emerging viral infections in the world, including recent SARS-CoV-2, MERS, ZIKV epidemics and discussing their possible origins, evolution, natural reservoir, mechanisms of adaptation to the human and potential risk factors.