Hello from JustAnswer.
There are two levels of answer to this question, but first, let me discuss the risk
in this situation.
The average risk to a male of a single episode of unprotected oral sex with an HIV positive partner is 0.005%, which also means that 99.995% of men do not become infected. If the HIV status of the partner is unknown, then the actual risk is much lower, although the amount lower would depend upon the prevalence of HIV in your community.
Now to discuss testing and the recommendations of the CDC. If someone has sex with someone that is known to be HIV positive, then the CDC recommends post-exposure prophylaxis
, rather than simple testing, so the question of testing usually only arises when the HIV status is unknown. The current recommendation of the CDC is that it is not necessary to be tested every time that someone has a sexual encounter with someone of unknown HIV status. Instead, the CDC recommends that everyone that is sexually active should be regularly tested for HIV. For most individuals, annual testing is adequate, but the frequency of testing can be adjusted based on sexual history.
So, if the current recommendations would be followed, there was no need to perform any specific testing because of this sexual encounter. However, it is appropriate to get annual testing.
Despite this recommendation, we see many patients that prefer to be tested after a questionable encounter. When testing is done after a specific encounter, then testing 17 days after a potential exposure would not be adequate. When there is an encounter that warrants testing, the recommendation is to perform testing initially at 4-6 weeks and then repeated at 3 months. The current generation of testing is more sensitive, and the average time to detection is 22 days, so most people will be detected by the first test. However, there still are some people in whom antibody development is slower, and it is not considered to be a reliable negative test until the test at 3 months is negative. There are viral load tests that can be positive more quickly, but they are not recommended to be done for testing after a questionable encounter.
So, the odds are very good that you would not be infected from a single encounter of oral sex and testing after such an encounter is not recommended. However, if testing is done for reassurance, it would need to be repeated at 3 months to be reliably negative.
If I can provide any further information, please let me know.