I am really confused about this matter. I've heard a lot of versions from doctors and on internet. To be more specific:

  1. A pathologist that claimed to have worked with HIV positive patients for 10 years told me that female to male transmission has close to zero possibility. She insisted that straight men cannot contact HIV (unless there is a sore on their genitals), and women contract HIV from men who have had sex with men (but do not admit it).

  2. A training pathologist told me that HIV transmission has less than 50% chance and all of that fuss is to urge people to use condoms.

  3. There are articles all over the internet that say that HIV is most common to gay people and women and straight men are very unlikely to contract the virus.

  4. When you get tested for HIV, the doctors tell you that there it is very likely to contract the virus regardless of your sex or sexual preferences (straight men and women, gay men and women) if your partner does NOT take medication (a chance higher than 95% if I remember correctly) and around 30-40% chance if the partner takes medication.

Can anyone tell me which of the above statements is valid?

NOTE: The above statements do not include transmission via syringe use and blood transfusion, with which the transmission rate is equal for all sexes.

  • 2
    I am skeptical of the claim in your first note that "every logical person would think the same". If there is no chance of STI transmission and contraception is already covered by other means (or if conception is desired), then I would expect many logical people to conclude that there is no need for condoms. Therefore, I suggest that you remove that claim, as it is unlikely to serve any purpose other than to distract from your primary question. Commented Jul 14, 2016 at 8:04
  • 1
    This question would be much more compelling with some notability references. It seems likely that you simply misunderstood the pathologist. It doesn't seem likely that doctors tell you that HIV doesn't have high-risk versus low-risk practices.
    – Oddthinking
    Commented Jul 14, 2016 at 12:32
  • It should be noted that any statistical numbers here will be just that, statistical. A scratch here, an inflammation there, and chances of transmission in a specific case can be pretty high.
    – DevSolar
    Commented Jul 14, 2016 at 13:21
  • 3
    I think this is a question for health.stackexchange.com. Where it is already posted, by the way. Please do not cross-post across several sites of the Stackexchange network. It fragments the answers.
    – Philipp
    Commented Jul 14, 2016 at 13:45

1 Answer 1


This systematic review and meta-analysis demonstrates there are many factors involved in the risk of the transmission of HIV in heterosexual acts.

In high-income countries, the risk of transmission of HIV from female-to-male is 0.04% per act [95% CI 0.01-0.14].

This sounds low - about 1 in 2500 encounters - but given the prevalence of straight sex and of HIV in women, that allows plenty of opportunity for HIV to spread to many people.

In low-income countries, the risk is increased drastically to 0.38% per act [95% CI 0.13-1.10]), but the evidence is poorer.

Genital ulcers increase the risk. Late-phase HIV infection increases the risk. Circumcision decreases the risk.

These are the figures without antiretrovirals; presumably they would lower the risk.

[I'd be remiss not to mention that condoms reduce the risk of HIV transmission. Please practice safe sex.]

  • 4
    when you say the risk is 0.04% per act, is that based upon some of the people using condoms, or only upon people who don't use condoms? Also, what hetrosexual acts are included?
    – DavePhD
    Commented Jul 14, 2016 at 13:06
  • 4
    "0.04% per act" - could you please clarify if this is this with prior assumption that the partner has HIV, or with any partner?
    – user5341
    Commented Jul 14, 2016 at 18:38
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    It should be highlighted that these kinds of figures are averages, and those individuals for which HIV transmission occur are probably nowhere close to the average a priori risk. There are many factors that increase the risk of HIV transmission risk (even beyond what is already stated), so we should not ignore those in favor of a low average risk. The average risk of pregnancy per act of unprotected vaginal intercourse is pretty small, but people get pregnant all the time. Commented Jul 14, 2016 at 19:44
  • 2
    "but given the prevalence of straight sex and of HIV in women, that allows plenty of opportunity for HIV to spread to many people" that statement is totally vague, if not completely nonsensical mathematically. It seems a shame to include pure fluff on a "skeptic" site. If you want to do a regression of what the spread would be based on that, go for it.
    – Fattie
    Commented Jul 15, 2016 at 15:05
  • 1
    @JoeBlow: AFAIK, the infectiousness of bodily fluids on skin is significantly lower than the infectiousness on mucous membrane. Condoms keep male precum and semen away from female mucous membrane, and female fluids from those parts of the penis that are mucous membrane (i.e., the tip). And it doesn't matter how high or low initial chances of infection are (and I am not argueing those numbers either way here); using a condom does reduce that by a given percentage.
    – DevSolar
    Commented Aug 19, 2016 at 14:13

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