What it means

HIV is a virus — the human immunodeficiency virus — that attacks CD4 cells, a type of white blood cell central to the immune system. AIDS is the advanced stage that can develop when HIV has damaged the immune system significantly without treatment.

That distinction is the single most important thing on this page: HIV and AIDS are not the same thing. Most people with HIV who have access to treatment will never develop AIDS.

How HIV is actually transmitted

What can vary

HIV often causes no symptoms at all, particularly in the early years. Many people have it for a decade without realising, which is why testing rather than symptoms is the only way to know. When symptoms do occur they are non-specific — flu-like illness, swollen glands, rash — and are easily mistaken for something else entirely.

Transmission risk varies enormously by act, by body site and by viral load. It is not a simple yes-or-no: a person on treatment with an undetectable viral load does not transmit HIV sexually, whereas the same person without treatment does.

  • Receptive anal sex carries the highest risk of transmission per act.
  • Shared needles and injection equipment carry high risk.
  • Oral sex carries low but non-zero risk.
  • There is no risk from kissing, sharing a room, sharing utensils, or from mosquito bites.

The window period, the length of time before a test can detect infection, is the period of highest infectiousness and greatest uncertainty. This is why timing a test matters.

HIV is transmitted through certain body fluids in certain situations:

  • Semen, vaginal fluid and rectal fluid
  • Blood
  • Breast milk
  • Vaginal and rectal fluids touching damaged mucous membranes

It is not transmitted through ordinary contact: sharing a room, food, plates, cutlery, toilets, towels, razors, swimming pools, mosquito bites, or hugging. It is not transmitted through saliva, sweat or tears. You cannot get HIV from kissing.

The window period

A test can only detect HIV once your immune system has responded. That period is usually a few weeks, commonly around 6-12 weeks, and sometimes longer. A test taken too soon may be negative without meaning you do not have HIV. This is why the timing of a test matters so much.

What treatment does

Antiretroviral therapy (ART) suppresses the virus to an undetectable level. Three things follow from that:

  1. The immune system recovers and can usually function normally.
  2. Life expectancy is close to normal with regular treatment and monitoring.
  3. A person on treatment with an undetectable viral load does not transmit HIV sexually. This is U=U — Undetectable equals Untransmittable — supported by strong evidence from large studies.

U=U applies to sexual transmission. It does not mean treatment can be paused: missing doses risks the virus becoming detectable again, which is both a health risk and a transmission risk.

PrEP and PEP

PrEP (pre-exposure prophylaxis) is medication taken by people who are HIV-negative and at ongoing higher risk, which greatly reduces the chance of acquiring HIV. It is a prescription requiring assessment and regular monitoring, and it does not replace other prevention.

PEP (post-exposure prophylaxis) is emergency medication taken after possible exposure. It must start as soon as possible and within 72 hours — earlier is much better. If that applies to you, this is urgent: go now, do not wait to think it over, and do not wait to see whether symptoms appear.

Warning signs

  • Possible exposure in the last 72 hours — go for PEP now. This is time-critical in a way nothing else on this site is.
  • Flu-like illness 2-4 weeks after possible exposure — fever, rash, sore throat, swollen glands. This can be acute HIV, and it is often missed because it resembles an ordinary cold. If you have had a possible exposure and then felt unwell, ask specifically whether PEP should be considered and whether you should be tested.
  • Testing: a negative result needs repeating if the window period has not passed.

What to do next

Get tested. Testing is routine in many settings and should not be a crisis. Ask about the window period so you know whether to retest.

If you may have been exposed in the last 72 hours, get PEP now.

If you test positive, you will be referred for treatment quickly, and effective treatment changes the outlook entirely.

Self-care

No self-care treats HIV, and ART does not work without taking it consistently. For most people that is a single daily pill or, in some countries, an injection every few months.

If you are living with HIV, your general health matters alongside ART — not smoking, moderate alcohol, staying up to date with vaccinations, and support for mental health are all worth discussing with your clinic.

When to seek help

Emergency: possible exposure within 72 hours — go now for PEP.

Prompt: flu-like symptoms after possible exposure; a negative test taken inside the window period.

Routine: routine testing, or starting PrEP.

How to talk about it

“I had a risk and I want PEP.”

“I need a repeat HIV test — when is my window period up?”

“I’ve been offered PrEP and I want to ask about it.”

“I tested positive and I don’t know what to do next.”

Any of these can go to a sexual health service, an emergency department, or a GP. If you are in the window period, say that first. You do not need to explain the whole situation to get the right care quickly.

Myths and stigma

“You can tell by looking.” You cannot. HIV has no visible signs, and many people with HIV have never had a test.

“It is spread by ordinary contact.” It is not. Not by kissing, sharing a room, sharing a toilet, sharing a cup, sharing food, or being in the same air.

“A positive result is a death sentence.” With regular treatment, life expectancy is close to normal, and an undetectable viral load means HIV is not sexually transmissible — U=U.

Stigma is not a side effect of HIV; it is one of the things that makes people avoid testing, which in turn makes transmission more likely.

Sources

Public sources are linked so you can read the detail rather than take this site’s word for it. None of this has yet been reviewed by a qualified clinician — see how we handle medical review.

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References

Where this comes from

Linked so you can check it against a recognised public health source rather than take this site's word for it.

  1. HIV — WHO World Health Organization (opens in a new tab)
  2. HIV — CDC US Centers for Disease Control and Prevention (opens in a new tab)

These are public sources from recognised health organisations, linked so you can read the detail rather than take this site's word for it. Reading them does not tell you whether any of it applies to you, and none of these articles has yet been reviewed by a qualified clinician. How we handle sourcing and review.