The pathogenesis of viral infections can be defined as how viruses cause disease in humans, animals, plants, or bacteria. Most knowledge of the pathogenesis of viral infections is based on experimental studies in laboratory animal models to understand natural infections in humans.

Most viral diseases are acute and chronic, which can have a significant impact on the patient's health. Today, thanks to diagnostic testing methods for viral infections, more than 500 different viruses can be detected, improving the effectiveness of human disease treatment.

Viruses are one of the infectious agents with very small size (diameter from 20-300mm), simple structure but the ability to cause disease in humans is extremely fast. Viruses have the basic characteristics of an organism but they do not have a cellular structure, cannot reproduce themselves and do not have metabolism.