A viral infection is the proliferation of a harmful virus within the body. Symptoms of the viral illness are due to tissue damage and the associated immune response of the host. Types of viral infections. Respiratory viral infections: Respiratory viral infections affect the nose, lungs and airway.
Viruses are small particles of genetic material (either DNA or RNA) that are surrounded by a protein coat. Some viruses also have a fatty “envelope” covering. They are incapable of reproducing on their own. Viruses depend on the organisms they infect (hosts) for their very survival. Viruses get a bad rap, but they also perform many important functions for humans, plants, animals, and the environment. For example, some viruses protect the host against other infections. Viruses also participate in the process of evolution by transferring genes among different species. In biomedical research, scientists use viruses to insert new genes into cells.