Generally, sexually transmitted infections (STIs) are on the increase. According to a Canadian study 'Research suggests that STIs can increase both an HIV-negative person’s risk of becoming infected with HIV as well as an HIV-positive person’s risk of transmitting HIV to someone else.' As many STDs/STIs such as Chlamydia can have no symptoms obvious, or at least not enough to seek medical diagnosis and as such is easy fro them to go un-diagnosed. They do however cause damage to the host such as inflamation and stress on the immune system. Almost all STIs are easily treatable once detected. Certain STDs/STIs once infected cannot be fully treated but can be managed. These include HPV, herpes and HIV.
Sexually transmitted infections are caused by bacteria, viruses and parasites entering the individual through unprotected sex. These foreign pathogens then go on to be detected by the immune system which in turn responds by attempting to attack the threat. This leads to the common symptoms associated STDs such as inflammation.
The inflammatory response is meant to help fight the pathogen by increasing immune cells CD4 at the site. HIV finds it easy to infect the CD4 cells once they have been activated by the immune system, so if an individual has these activated CD4 cells in an STD infected site such as a mouth, vaginal or anal area then HIV will find it easier to infect that individual. Additionally, the infected site may ulcerate causing a break in the barrier or a 'hole' by which HIV can enter.
The take away from this is that it's important to keep good sexual health at all time. That undiagnosed Chlamydia or Gonorrhea infection can be putting you at increased risk of HIV. Practice safe sex and if you have practised unprotected sex then get tested for all common STDs/STIs as soon as is practical. You can use multi-pack STD test kits or visit your local STD clinic or discuss options with your medical practicioner.