Does gay sex transmit diseases other than HIV?

Hello and welcome to e health forum.

In case, both the partners are not infected, then there is no risk of any infections including HIV.

Sexually transmitted infections like HIV, hepatitis B, hepatitis C, Herpes, Chlamydia, gonorrhea, HPV, Syphilis - are transmitted when individuals have a risky sexual behavior.

Risky sexual behavior includes
1. Having multiple sexual partners,
2. Having intercourse without protection
3. Use of alcohol and Illegal drugs like methamphetamine, and other “party
drug” use - can lead to risky sexual behavior, due to reduced inhibition.
4. Low socio economic status, and psychiatric illnesses - can lead to higher rates of emotional distress, suicide attempts, substance use, and risky sexual behavior.

The primary mode of transmission of HIV between men is through anal sex without a condom.

Gonorrhea and chlamydia are sexually transmitted by genital secretions, such as urethral secretions from the ‎penis.

Genital herpes and syphilis are transmitted primarily through skin-to-skin contact with sores / ulcers or infected skin ‎that looks normal.

HPV is transmitted through contact with infected genital skin or mucosal surfaces / secretions, such as the penis and ‎anus.

SAFE SEX - The ABC 's to prevent STDs include -

A - Abstinence (not engaging in sex, or delaying first sex)
B - Being tested for HIV and Being faithful in marriage and monogamous relationships or reducing the number of sexual partners
C - Use a Condom, correctly or consistently, if you are not faithful.

Abstinence from vaginal, anal, and oral intercourse is the only 100% effective way to prevent HIV and other STDs. The correct and consistent use of male latex condoms can reduce the risk of STD transmission, including HIV infection. However, no protective method is 100% effective, and condom use cannot guarantee absolute protection against any STD.

I hope this helps.