A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infectious virus particles (virions) attach to and enter susceptible cells.
Examples include the common cold, gastroenteritis, COVID-19, the flu, and rabies.
A vertically transmitted infection is an infection caused by pathogenic bacteria or viruses that use mother-to-child transmission, that is, transmission directly from the mother to an embryo, fetus, or baby during pregnancy or childbirth. It can occur when the mother has a pre-existing disease or becomes infected during pregnancy. Nutritional deficiencies may exacerbate the risks of perinatal infections. Vertical transmission is important for the mathematical modelling of infectious diseases, especially for diseases of animals with large litter sizes, as it causes a wave of new infectious individuals.
View the full Wikipedia page for Vertically transmitted infection