HIV: transmission, acute infection symptoms and the difference with AIDS

What exactly is HIV?

HIV (human immunodeficiency virus) attacks the cells that defend the body against infections. Without treatment it gradually weakens the immune system. AIDS is not the virus: it is the advanced stage of infection, when defences are so damaged that “opportunistic” illnesses (tuberculosis, severe pneumonia, some cancers) take hold.

The good news, and the key message from Santé publique France: an HIV-positive person treated early does not develop AIDS, has a near-normal life expectancy and, once their viral load is undetectable, no longer transmits the virus to partners (see undetectable viral load).

How is HIV transmitted?

According to WHO, HIV is passed on through certain body fluids of a person living with HIV: blood, semen, pre-cum, vaginal and anal fluids, breast milk. In practice, between men, the risky situations are:

• anal sex without a condom or PrEP, especially for the bottom (the anal lining is thin and absorbs easily);
• oral sex with ejaculation in the mouth, a lower but real risk when the partner has a high viral load;
• sharing injecting or snorting equipment (slamming, chemsex);
• practices involving bleeding (fisting without gloves, SM with blood).

HIV is not transmitted by saliva, kissing, touching, sweat, urine, toilets or everyday objects.

An often-forgotten point: having another STI (syphilis, gonorrhoea, herpes…) increases the risk of getting or passing on HIV. Sexosafe puts it at roughly three times higher.

What are the symptoms of acute HIV infection?

Acute (primary) infection covers the first weeks after infection. The virus multiplies very fast: this is when people are most infectious without knowing it. WHO and Sexosafe describe flu-like signs:

• fever, unusual tiredness;
• sore throat, headache;
• a rash of small spots on the body;
• swollen glands (neck, armpits, groin), sometimes diarrhoea.

These symptoms usually appear 2 to 4 weeks after exposure and go away on their own. Many people have none at all. In other words: you cannot know whether you have HIV without a test. If you get these signs after a risky encounter, tell the doctor and ask for an HIV test: a lab test can pick up infection very early.

HIV and AIDS: why the difference matters

Without treatment, infection progresses silently for years before defences collapse (AIDS). With antiretroviral treatment, this progression is stopped. In France in 2024, Santé publique France estimates that about 5,100 people found out they were HIV-positive, and 43% were diagnosed late: that is why regular testing matters so much.

How can you protect yourself?

There is now a real prevention “toolbox”:

1. PrEP: preventive treatment, as pills or injections, highly effective against HIV.
2. Condoms, which also protect against some other STIs (how to use them well).
3. TasP: an HIV-positive person on effective treatment does not pass on the virus.
4. PEP, emergency treatment best started within 4 hours and no later than 48 hours after exposure.
5. Regular testing, every 3 months if you have several partners.

What should I do if I took a risk?

Less than 48 hours ago: go to an emergency department or a sexual health clinic to be assessed for PEP. More than 48 hours: get tested (a lab test 6 weeks after exposure gives a definitive result, see window period) and protect your partners in the meantime. In France, Sida Info Service answers on 0 800 840 800, free and anonymous.