A viral infection is a disease that occurs when pathogenic viral particles enter the body. Viruses attack normal living cells in the body. They use these cells to replicate and amplify, ultimately destroying the host cell - this is what causes the symptoms of a viral infection. Many of them, such as ARVI, go as usual, and the body recovers on its own, while others, such as HIV, do not. Viral diseases are extremely common infections. There are many types of pathogens that cause a wide variety of viral diseases.