Final answer:
Most STIs are asymptomatic or cause very mild symptoms, especially in females. However, they can still be transmitted to others and may lead to serious health problems if left untreated.
Step-by-step explanation:
Most STIs are asymptomatic or cause very mild symptoms, especially in females. Some common symptoms of STIs include genital sores or rashes, vaginal or penile discharge, and painful urination. However, many cases of STIs are silent infections, meaning they go unnoticed because they do not cause noticeable symptoms. It is important to note that even in asymptomatic people, STIs can still be transmitted to others and may lead to serious health problems if left untreated.