You have brought up an interesting question. Two people who have never been sexually active should not pose a risk for contracting an STI/STBBI (sexually transmitted and blood borne infections) between themselves, unless they have been exposed to STBBIs from non sexual transmission.
However, there are some STBBIs that can also spread through non-sexual ways like herpes, HIV, Hep B and Hep C. Some instances where someone who is not sexually active but have an STBBI include:
- Someone who was born with HIV because of an HIV positive parent
- Someone who has acquired HIV, Hep B or Hep C through shared drug equipment
- Someone who has acquired herpes through kissing
These STBBIs can later be transmitted sexually.
Assuming that our partner(s) has never had a sexual exposure can put us at risk of contracting STBBIs, because many a times STBBIs do not have noticeable symptoms. So the surest way to ensure safer sex is by getting tested and treated.
If two people have been tested, are only engaging in sex with each other and not sharing drug use equipment there is little to no STBBI risk. Conversation with partner about STBBIs, testing, treatment, number of sexual partners, prevention for people who use drugs, goes a long way in staying safe and healthy and open up choices for engaging in condomless sex.