Hello from JustAnswer.
Actually, no, but we typically will treat partners anyway.
The likelihood of infection from each sexual encounter is fairly high, about 30-40%. The risk of male-to-female transmission is higher and will be in the upper portion of this range, while female-to-male transmission will be in the lower end of this range. (The personal information that you gave when you registered for the site is blocked, so your gender is not available to me, but the answer is the same regardless of gender.) Obviously, with multiple exposures in an ongoing relationship, the likelihood of transmission will get progressively higher and will approach 100%. But in any situation with a time-limited number of exposures, there is a statistical possibility that the partner would not get infected. If you were infected long ago and the number of exposures are greater, then it will be closer to 100%.
However, even if you were just infected last week and it was detected today after only a few sexual encounters with this partner, we would still typically want to treat the sexual partner. Our testing for chlamydia has gotten progressively better, but there is still a small chance that testing could miss the germ, so we still will typically treat a known recent sexual contact without performing testing.
If I can provide any additional information, please let me know.