Why do people infect other people before they show symptoms?

People can infect others before showing symptoms due to the incubation period of many Infectious Diseases, during which the pathogen replicates in the host without causing noticeable signs of illness. This asymptomatic transmission allows individuals to unknowingly spread the infection, as they may not be aware they are contagious. Additionally, certain viruses, like COVID-19 and influenza, have a higher likelihood of being transmitted during this pre-symptomatic phase, increasing the challenge of controlling outbreaks.