Infectious diseases continue to be the largest cause of human and animal morbidity and mortality, resulting in enormous global healthcare expenditure. Many infectious diseases have caused outbreaks and epidemics over the world. Infectious viral infections are a never-ending threat that might appear or reappear in unexpected places and at inappropriate times. In the emergence or re-emergence of viral infectious illness, human, ecological, and virus-related factors all play a role. Despite significant advancements in the medical field, the development or re-emergence of novel pandemic viruses remains a persistent challenge in human health. Emerging infections can be characterised as diseases whose incidence has increased in recent decades or has the potential to increase in the future.