HIV Risk Assessment Calculator
Calculate HIV transmission risk based on exposure factors
How to Use
- Select the type of exposure you experienced
- Indicate whether a condom was used during the exposure
- Select your partner's HIV status if known
- Click calculate to see your estimated risk level
- Seek immediate medical care if exposed within 72 hours for PEP
Understanding HIV Transmission Risk
HIV (Human Immunodeficiency Virus) transmission risk varies significantly based on the type of exposure, use of protection, and the HIV-positive partner's viral load. This calculator uses CDC per-act transmission estimates to provide educational risk assessments.
It's crucial to understand that these are statistical estimates for single exposures. Any potential exposure to HIV should be taken seriously, and immediate medical consultation is recommended.
HIV Transmission Routes
| Exposure Type | Risk per 10,000 Exposures (Without Protection) | Risk Level |
|---|---|---|
| Receptive anal intercourse | 138 | Very High |
| Needle sharing | 63 | Very High |
| Insertive anal intercourse | 11 | High |
| Receptive vaginal intercourse | 8 | Moderate |
| Insertive vaginal intercourse | 4 | Moderate |
These estimates are from the CDC and represent average risks. Individual risk can vary based on factors like viral load, presence of STIs, and mucosal integrity.
HIV Prevention Strategies
Multiple effective strategies exist to prevent HIV transmission:
- Condoms: Reduce transmission risk by approximately 95% when used consistently and correctly
- PrEP: Pre-exposure prophylaxis reduces risk by about 99% when taken daily as prescribed
- U=U: People with HIV who maintain undetectable viral loads cannot transmit HIV sexually
- PEP: Post-exposure prophylaxis can prevent infection if started within 72 hours
- Regular testing: Know your status and your partner's status
- Avoiding needle sharing: Use sterile needles if injecting drugs
- Treatment as prevention: HIV-positive individuals on treatment protect their partners
Post-Exposure Prophylaxis (PEP)
PEP is emergency medication taken after potential HIV exposure. It consists of antiretroviral drugs taken for 28 days and can prevent HIV infection if started quickly enough.
Timing is critical: PEP must be started within 72 hours of exposure, with effectiveness decreasing over time. Starting within 24 hours provides the best protection. PEP is available at emergency rooms, sexual health clinics, and some primary care providers.
Common PEP regimens include combinations of tenofovir, emtricitabine, and raltegravir or dolutegravir. Side effects may include nausea, fatigue, and headache, but these are usually manageable.
Pre-Exposure Prophylaxis (PrEP)
PrEP is a daily medication for HIV-negative people at high risk of HIV infection. When taken consistently, it's highly effective at preventing HIV.
PrEP is recommended for people who have an HIV-positive partner, have had multiple sexual partners, have been diagnosed with an STI in the past 6 months, inject drugs, or engage in transactional sex.
Common PrEP medications include Truvada (tenofovir/emtricitabine) and Descovy. PrEP requires regular medical monitoring including HIV testing every 3 months and kidney function tests. It does not protect against other STIs, so condom use is still recommended.
U=U: Undetectable Equals Untransmittable
U=U is a scientifically proven concept: people living with HIV who take antiretroviral therapy daily as prescribed and achieve and maintain an undetectable viral load cannot sexually transmit HIV to others.
Multiple large studies including PARTNER and PARTNER2 have confirmed that there were zero HIV transmissions from HIV-positive partners with undetectable viral loads, even after tens of thousands of condomless sex acts.
Maintaining an undetectable viral load requires consistent adherence to HIV treatment and regular viral load monitoring (typically every 3-6 months).
Importance of HIV Testing
Regular HIV testing is crucial for sexually active individuals and anyone who may have been exposed to HIV. Early detection allows for prompt treatment, which improves health outcomes and prevents transmission.
- CDC recommends at least annual testing for sexually active individuals
- More frequent testing (every 3-6 months) for those at higher risk
- Window period: Modern tests can detect HIV 18-45 days after exposure
- Free and confidential testing available at many health departments and clinics
- Rapid tests provide results in 20 minutes; confirmatory testing may be needed
- Home HIV tests are available for private testing
Frequently Asked Questions
- How accurate is this HIV risk calculator?
- This calculator uses CDC per-act transmission estimates based on large epidemiological studies. However, individual risk varies based on many factors not captured here, including viral load, presence of STIs, genital trauma, and immune status. This is an educational tool only - always consult healthcare professionals for personalized risk assessment.
- What should I do if I've had a recent HIV exposure?
- Seek immediate medical attention if exposure occurred within the last 72 hours. PEP (post-exposure prophylaxis) can prevent HIV infection but must be started quickly - ideally within 24 hours, and no later than 72 hours after exposure. Go to an emergency room, sexual health clinic, or contact your healthcare provider immediately.
- Does U=U really mean zero transmission risk?
- Yes. Multiple large scientific studies have conclusively shown that people with HIV who maintain an undetectable viral load through consistent antiretroviral treatment cannot sexually transmit HIV to their partners. This is one of the most important advances in HIV prevention and care.
- How effective are condoms at preventing HIV?
- When used consistently and correctly, condoms reduce HIV transmission risk by approximately 95%. They are highly effective but not 100% protective. Combining condoms with other prevention methods like PrEP provides even greater protection.
- Who should consider taking PrEP?
- PrEP is recommended for HIV-negative people at substantial risk: those with HIV-positive partners not on treatment or without undetectable viral load, people with multiple sexual partners, recent STI diagnosis, inconsistent condom use with partners of unknown status, or people who inject drugs. Talk to your healthcare provider to see if PrEP is right for you.
- When should I get tested for HIV after potential exposure?
- Modern HIV tests can detect infection 18-45 days after exposure depending on the test type. For potential exposures, testing is recommended at 6 weeks and again at 3 months for definitive results. However, if you've had recent exposure, seek PEP immediately rather than waiting to test.