Emerging and Re-emerging Viral Infections in the 21st Century: Microbiological and Public Health Perspectives

Pathogens, especially viruses and bacteria are known to have great potential to emerge and evolve for thousands of years and it seems to be a never-ending process. In the last couple of decades, many viruses have reemerged, and several novel viruses have emerged from animals and birds, posing a serious threat to human health and the global economy. Amongst these pathogens, RNA viruses were found to be more pathogenic and are more frequently associated with emerging viral diseases. This is because they have the capabilities to adapt rapidly to changing local and global environments. The ability to undergo mutation, genetic assortment, and recombination, unavailability of effective vaccines, and lack of herd immunity are the compounding factors for the emergence of new diseases and reemergence of old viral diseases. This article outlines virus characteristics, source and transmission of infection, recent outbreaks, and impact on human health, laboratory diagnosis, and preventive strategies of the prominent epidemic and pandemic viral diseases that occurred globally in the 21st century.