What are $STIs$? Give information about diseases caused by them.

(N/A) Infections or diseases that are transmitted through sexual intercourse are collectively called sexually transmitted infections $(STIs)$,venereal diseases $(VD)$,or reproductive tract infections $(RTIs)$.
Examples include gonorrhoea,syphilis,genital herpes,chlamydiasis,genital warts,trichomoniasis,hepatitis-$B$,and $HIV$ infection,which is the most dangerous.
Some infections like hepatitis-$B$ and $HIV$ can also be transmitted by sharing injection needles,surgical instruments with infected persons,blood transfusion,or from an infected mother to the foetus.
Except for hepatitis-$B$,genital herpes,and $HIV$ infections,other diseases are completely curable if detected early and treated properly.
Early symptoms include itching,fluid discharge,slight pain,and swellings in the genital region. Infected females may often be asymptomatic,leading to delayed detection.
The social stigma attached to $STIs$ often deters individuals from seeking timely treatment,which can lead to complications such as pelvic inflammatory diseases $(PID)$,abortions,stillbirths,ectopic pregnancies,infertility,or cancer of the reproductive tract.