Human viruses: An ever-increasing list

It has been 124 years since yellow fever was demonstrated to be caused by a ‘filterable agent’. While long-standing viral diseases, with the exception of smallpox, continue to be endemic, new ones have been emerging intermittently, primarily from a substantial zoonotic reservoir, leading to significant socioeconomic consequences. Currently, we are contending not only with the ongoing COVID-19 pandemic but with surges of various other viral infections. Recent metagenomic analyses have revealed a variety of novel human viruses whose health implications remain largely unclear. The following questions arise: How many human viruses have been identified? Which of these viruses are etiological agents of human diseases? This review aims to address the two inquiries and highlight the viruses that pose significant public health threats as outlined in the World Health Organization’s Fact Sheets. Importantly, many human viruses are preventable; appropriate precautions can be implemented to mitigate the risk of infection.