Viral diseases are illnesses caused by viruses, which are tiny infectious agents that can only replicate inside the living cells of an organism. Common examples of viral diseases include the flu, common cold, and COVID-19. These viruses can spread from person to person through various means, such as coughing, sneezing, or touching contaminated surfaces. Preventing viral diseases often involves good hygiene practices, like washing hands regularly and getting vaccinated. Vaccines, such as those for measles or influenza, help the body build immunity against specific viruses. Understanding how these diseases spread and how to protect ourselves is essential for maintaining public health.