Viral pathogens are tiny infectious agents made up of genetic material, either DNA or RNA, surrounded by a protein coat. They can only replicate inside the living cells of a host organism, such as humans, animals, or plants. Common examples of viral pathogens include influenza virus, HIV, and coronavirus. These viruses can cause a wide range of diseases, from mild illnesses like the common cold to severe conditions such as COVID-19 or Ebola. Transmission often occurs through direct contact, respiratory droplets, or contaminated surfaces, making prevention and control measures essential in public health.