Even afterward, there is something you can do.

IMAGE: Mexican campaign against discrimination toward HIV carriers
http://blog.uncovering.org/en/archives/2007/03/against_the_discrimination_of_hiv_carriers.html

Following from the previous item about PRE-exposure drugs, here is a discussion of a treatment that is already available to people who might have just been exposed to HIV.

Gay men may not be accessing HIV post-exposure prophylaxis (PEP) in situations when its use would be warranted, a study published in the online edition of Sexually Transmitted Infections suggests.

Investigators in Brighton conducted interviews with 15 gay men who were currently taking, or had recently completed, a course of post-exposure prophylaxis after unprotected anal intercourse. They found that prior to accessing this treatment, the men generally had a poor understanding of what post-exposure prophylaxis involved.

Post-exposure prophylaxis (a short course of treatment with antiretroviral drugs after possible exposure to HIV) is becoming increasing available for individuals reporting sexual risk behaviour. The number of gay men presenting for such treatment has increased following targeted advertising campaigns and the publication of professional guidelines.

There is robust evidence that post-exposure prophylaxis can prevent infection with HIV. But there have been reports of HIV infection despite its use following possible sexual exposure to the virus. In many instances these infections can be attributed to ongoing sexual risk behaviour.