Guide Contents

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What Determines HIV Risk?

HIV transmission is determined by a number of different variables that can be estimated and combined. This guide walks through the main drivers of risk that we use to generate your 6 page personalized assessment which is powered by data from the CDC and UNAIDS.


This first section explains the general logic behind HIV transmission. To see how these factors combine for your exact encounter, you will need a personalized calculation.

Partner HIV status and prevalence

The starting point is the chance that your partner has HIV. This varies based on:

  • Country and region.
  • Gender and sexual network.
  • Sexual orientation and local prevalence in that group.
  • Whether the partner is on treatment and virally suppressed.

Your personalised report estimates partner HIV likelihood using epidemiological data that matches the location and scenario you describe.

Type of sex or contact

Different types of sex have different levels of HIV transmission likelihood. In general:

  • Receptive anal sex is associated with the highest per act risk.
  • Insertive anal sex has a lower but still meaningful risk.
  • Receptive vaginal sex carries lower risk than receptive anal sex.
  • Insertive vaginal sex is lower again.
  • Oral sex is usually very low to negligible in most circumstances.
  • Non penetrative contact such as external rubbing is effectively zero for HIV.
  • Fingering or hand to genitals is effectively zero unless there is significant fresh blood and open wounds on both sides.

Condom use and integrity

Condoms provide strong protection against HIV when they are used correctly and remain intact. Consistent condom use reduces HIV transmission by at least 80 percent compared with no condom use.

If a condom stayed on, did not slip, and did not break, HIV risk from a single encounter is usually very low for vaginal or anal sex. If there was a clear break or it slipped off, your personalized report adjusts the calculation to reflect unprotected exposure.

Viral load and treatment (ART)

When someone with HIV takes antiretroviral therapy and maintains an undetectable viral load, they do not transmit the virus through sex. This is often summarised as Undetectable equals Untransmittable, or U equals U.

Your report uses country level treatment and viral suppression data as part of the partner risk estimate, especially when partner status is unknown.

Wounds, inflammation, and other infections

Open cuts, sores, or significant inflammation in the genital or anal area can raise HIV transmission risk, especially in unprotected anal or vaginal sex. Other sexually transmitted infections can also increase susceptibility.

Your personalised report incorporates this information through a simple set of questions about cuts, irritation, and other infections if you choose to share that detail.

The HIV Risk Scale

The table below provides a simple overview of typical risk levels for common scenarios, before any personal details are applied. Your personalized report refines these to your specific situation.

Scenario Typical risk level
Receiving oral sex Extremely low
Giving oral sex Very low
Protected vaginal sex Very low
Unprotected insertive vaginal sex Low
Unprotected receptive anal sex Higher
Protected anal sex Low to very low
Fingering, hand to genitals, dry humping Effectively zero

These ranges are general. Your report uses more precise per act probabilities, partner prevalence, and modifiers to generate a personalised number for your own exposure.

Most Common Scenarios Explained

HIV Testing Timeline Calculator

Knowing when you can test and trust the result is often just as important as knowing the probability itself. This section gives general windows, however your personalized report uses your actual encounter date to generate exact earliest and conclusive test dates, based on the best available evidence from organisations such as CDC.

OraQuick and similar oral swab tests

  • Begin to detect many infections around three weeks after exposure.
  • Considered conclusive at twelve weeks for most guidelines.

Fourth generation blood tests

  • Detect many infections around fourteen days after exposure.
  • Usually considered conclusive at forty five days for a single high risk event.

PCR or RNA tests

These tests detect viral genetic material directly and can identify infection earlier than antibody or antigen tests. They are not routinely recommended for standard screening, but they may be used in specific high risk or clinical situations.

Your HIVRISKREPORT output calculates personalised earliest and conclusive testing dates based on the exact date of your encounter and the type of test you plan to use.

PEP: Emergency HIV Prevention After Exposure

Post Exposure Prophylaxis, often shortened to PEP, is a course of HIV medication that can reduce the chance of infection after a high risk exposure. It is time sensitive and must be started quickly.

  • PEP must be started within seventy two hours of the exposure.
  • It is most effective when started within the first twenty four hours.
  • It is usually recommended for specific higher risk situations such as unprotected receptive anal sex with a partner known to be HIV positive or in a high risk group.

If your encounter was more than seventy two hours ago, PEP is no longer an option. In that case the focus shifts to accurate testing at the right times, which your personalised report can help you plan.

Always speak to a local sexual health clinic or emergency department if you think you may need PEP. This site does not replace medical advice.

How Your Personalised Risk Is Calculated

The HIVRISKREPORT engine takes the details from your assessment and converts them into a step by step probability calculation. In simple terms, it does three things.

  1. Estimates how likely it was that your partner had HIV.
    This uses country and group specific prevalence data, plus information about the type of partner and any known status or treatment details, using inputs from CDC, UNAIDS, and other public health sources.

  2. Applies a per act transmission probability for the type of sex.
    The calculator selects a probability that matches your role, the act, and whether it was anal, vaginal, or oral sex.

  3. Adjusts the risk with modifiers.
    This includes condom protection, possible wounds or inflammation, country level treatment coverage, and other relevant factors.

The final output is a percentage and a "1 in X" estimate that reflect the chance of HIV transmission from that specific encounter, based on the information you provide and the studies that underpin the model.

The tool is also independently scored with an external trust rating of 83 out of 100. You can view the trust report here if you want an outside check on site safety before ordering.

Why You Can Trust This Tool

HIVRISKREPORT was created because anxiety after a sexual encounter can become overwhelming. People search the internet, see worst case stories, and struggle to think clearly. Putting numbers on the situation does not erase risk, but it can help bring fear down to something more manageable.

The model behind the report is based on published research rather than guesswork. Key sources include:

  • Per act HIV transmission risk meta analyses.
  • Country level prevalence and treatment coverage data from organisations such as CDC and UNAIDS.
  • Studies on condom effectiveness and viral suppression.

On top of that, the site has been reviewed by an independent trust checker and currently holds an external trust rating of 83/100. You can view the external trust report if you want to verify this yourself before using the calculator or paying for a report.

You remain anonymous when you use the tool. The goal is to provide clarity and structure to a situation that often feels chaotic and frightening.

“A great counterweight to all the panic posts on Reddit. It greatly reduced my anxiety related to a recent “incident” and I am forever grateful that you took the time and effort in creating this service.”

- VERIFIED USER

More HIV Risk and Testing Resources

Disclaimer

HIVRISKREPORT is an informational and educational tool. It does not replace medical advice, diagnosis, or treatment from a qualified healthcare professional. If you think you may have been exposed to HIV, or if you feel unwell, contact a sexual health clinic, your doctor, or an emergency service in your area.

Ready for a personalized HIV risk calculation based on your exact scenario? START MY ASSESSMENT