How Sexually Transmitted Infections (STIs) Spread

How can an infection pass between people even when nobody looks or feels ill? The answer begins with the word “infection”, not with appearance, identity or character. A sexually transmitted infection (STI) is an infection that can be passed between people through sexual contact, but STIs are a varied group rather than one single illness. The central idea is that the route of possible spread is shared, while the infectious agent and effects can differ.