It depends on whether you are on treatment or not. If you aren’t treating HIV, then yes, contracting an STI can cause an increase in viral load. For example, having syphilis can cause a big increase in the viral load, making it more likely for you to pass on the virus. That’s why it is important to get regular sexual health check-ups and to get your viral load tested after you have had an STI. However, for people who are currently on HIV treatment, STIs appear to have no or very little impact on viral load.