HIV has changed beyond recognition since the 1980s. The virus hasn't gone away — but what it means to live with it, and the tools available to prevent it, have transformed completely.

This article is the foundation. Read it once and you'll understand the references in almost every other article on this site.

What HIV Actually Is

HIV stands for Human Immunodeficiency Virus. It attacks CD4 T-cells — the cells that coordinate your immune system's response to infection. Without treatment, the virus depletes these cells over years until the immune system can no longer fight off infections it would normally handle easily. That stage is called AIDS (Acquired Immunodeficiency Syndrome).

The key word is "without treatment." With modern antiretroviral therapy (ART), a person with HIV can live a full lifespan, maintain a normal immune system, and — at undetectable viral load — not transmit the virus to sexual partners.

How HIV Transmits

HIV transmits through specific body fluids: blood, semen and pre-seminal fluid, rectal and vaginal secretions, and breast milk. The virus must enter the bloodstream or contact mucous membrane tissue.

By sexual act (receptive partner, no protection, per-act risk estimates):

Act Approximate risk per act
Receptive anal sex ~1.4% (highest-risk sexual act)
Insertive anal sex ~0.11%
Receptive oral sex Very low — no confirmed cases in recent large studies
Insertive oral sex Negligible

These are population averages. Risk is higher with a higher viral load in the transmitting partner, with concurrent STIs (which can increase transmission ~3x), and during anal sex with tissue damage. Risk is lower — effectively zero — with an undetectable positive partner, consistent PrEP use, or consistent condom use.

ℹ Note

HIV does not transmit through kissing, saliva, sweat, tears, sharing food or drinks, toilet seats, swimming pools, hugging, or any casual contact. These fears were weaponised against gay men in the early epidemic. They have no scientific basis.

The Prevention Toolkit

You don't need to rely on any single tool. The goal is layered protection.

PrEP (Pre-Exposure Prophylaxis) A once-daily pill (or injectable every 2 months) taken by HIV-negative people that reduces HIV acquisition risk by 99%+ when used consistently. This is the most effective HIV prevention tool available for sexually active people. See PrEP Mechanics.

U=U (Undetectable = Untransmittable) An HIV-positive person on effective treatment with a sustained undetectable viral load cannot sexually transmit HIV. This is confirmed by multiple large-scale studies (PARTNER, PARTNER2, Opposites Attract) with zero transmissions across tens of thousands of condomless sex acts. See the U=U article for the full science.

Condoms When used correctly and consistently, condoms reduce HIV transmission risk by approximately 85%. They also protect against bacterial STIs (gonorrhoea, chlamydia) that PrEP does not.

PEP (Post-Exposure Prophylaxis) A 28-day course of antiretroviral medication taken within 72 hours of a potential HIV exposure. Approximately 80-99% effective when started promptly. See PEP: The Emergency Brake.

HIV Testing

Types of tests:

  • 4th-generation antigen/antibody test (Ag/Ab combo test): Detects HIV at 28 days post-exposure with high accuracy. The standard at sexual health clinics.
  • RNA/NAT test (nucleic acid test): Can detect HIV as early as 10 days. Used in some clinics, not universally available.
  • Rapid antibody tests (home tests, community testing): Older technology — detects antibodies only, reliable at 90 days, less reliable at 28 days. Useful for regular screening, not for post-exposure assessment.

Testing frequency recommendation: Every 3 months if you have multiple partners or concurrent partners. At minimum every 6 months if sexually active.

Window period: The time between infection and when a test reliably detects the virus. For 4th-gen tests: 28 days for near-definitive results (some guidelines say 45 days for complete certainty). A negative result at 28 days post-exposure is highly reassuring.

Acute HIV Infection

Approximately 40–90% of people newly infected with HIV experience a flu-like illness 2–4 weeks after infection. Symptoms include:

  • Fever
  • Swollen lymph nodes (especially in the neck, armpits, groin)
  • Sore throat
  • Rash (often a diffuse red rash on the trunk)
  • Muscle aches, fatigue
  • Sometimes: oral ulcers

These symptoms are identical to many viral illnesses — the only way to know if they're HIV is to test. If you've had a potential high-risk exposure in the past 2–4 weeks and develop these symptoms, get an RNA test (not just an antibody test, which won't yet be positive). If it's confirmed HIV, starting treatment early leads to better long-term immune outcomes.

Living with HIV

HIV is now a manageable chronic condition for people with access to medication. Modern single-tablet regimens are taken once daily, have very low side-effect profiles, and allow a completely normal lifespan.

An HIV-positive person on treatment with an undetectable viral load:

  • Cannot sexually transmit HIV (U=U)
  • Has a near-normal life expectancy
  • Can have HIV-negative partners and biological children without transmitting the virus

The stigma attached to HIV is a relic of an era when diagnosis was a death sentence. In 2026, it is not. A person disclosing an HIV-positive, undetectable status in a sexual context is demonstrating exactly the health-conscious, transparent behaviour you want in a partner.

Key Terms Reference

Term Meaning
ART Antiretroviral therapy — the medication regimen that suppresses HIV
Viral load The amount of HIV in the blood, measured in copies per mL
Undetectable Viral load below the threshold of detection (usually <50 or <20 copies/mL)
CD4 count Measure of immune health — normal range 500–1500 cells/mm³
Serodiscordant A couple where one partner is HIV-positive and one is negative
Seroconversion The point at which HIV antibodies become detectable after infection
U=U Undetectable = Untransmittable — zero transmission risk from undetectable partner

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