Here's why you need routine testing

"Regardless of what type of trust and relationship boundaries you have established with your partner, you want to incorporate regular STI testing as part of your routine health screenings because there's a lot of complexity in STI testing that's not well known," said Jenelle Marie Pierce, Executive Director of The STI Project and spokesperson for Positive Singles in Asheville, North Carolina. 

Pierce stressed that it's common for STIs to go undetected, in part, because of a difference between the incubation period (the time it takes for symptoms to present themselves) and the window period (the time it takes for an infection to show up on a test). For example, HIV infections have a window period of 45 days, meaning it may take up to 45 days before they are detectable by modern lab tests.

"If you test too soon, you might think you are negative but actually have an undetected infection," Pierce explained. "STI tests look for the pathogen or for your body's response to the pathogen, and either the infection itself needs enough time to replicate in order to be detectable or your body needs enough time to respond to the infection in order for your body's response to be detectable."

Many STIs have latency periods, meaning it can take weeks, months or years before they show symptoms. For example, syphilis, hepatitis B and HIV are common conditions that can remain dormant for years after contraction. Others, including HPV, chlamydia and gonorrhea, are often asymptomatic.

"Most people assume they'll know if they have an STI, but the most common symptom is no symptom, so the only way to know is to get tested," Pierce noted.

Then there are STIs with multiple transmission methods.

"What designates something as an STI is quite literally only related to how it is primarily contracted," Pierce added. "There are some infections that are almost exclusively transmitted through sexual activities, there are some infections that can be transmitted both sexually and nonsexually, and there are others that are rarely transmitted sexually."

For example, hepatitis B and HIV can be transmitted through blood-to-blood contact, the sharing of syringes or equipment to inject drugs, body piercing equipment and tattooing needles. Herpes and syphilis can be spread through skin-to-skin contact. There are even STIs such as molluscum contagiosum that can be spread not just through skin contact, but also with wet towels, gym equipment and tanning beds.