Emerging and reemerging viral infections in globe with special emphasis in India - A review

Abstract

It has long been recognized that pathogens, such as viruses, parasites, and other microorganisms, emerge and change over time. Viruses are powerful infectious agents that have co-evolved with humans and are responsible for several serious illnesses in people. There is no herd immunity for most humans, making emerging viruses, particularly the RNA viruses, more dangerous. The high mistake rate of the polymerases that copy the RNA viruses' genomes gives them the ability to adapt to the quickly changing local and global environments. Through mutation (as in the case of Dengue viruses), reassortment (as in the case of influenza viruses), and recombination, they can evolve at a rapid rate (polioviruses). The influenza A viruses (such as H1N1 and H5N1), which have caused numerous outbreaks, epidemics, and pandemics around the world, are the finest example of viruses emerging and reemerging. The complex host-pathogen ecology and the co-evolution of microbes with their hosts are linked to the emergence and reemergence of novel diseases. Human viral illness emergence and reemergence is an ongoing problem that affects a nation's social and economic growth.