What Is HIV, How Is It Spread, and How Is It Different From AIDS?

Many people who come to talk to me about HIV use the words "AIDS" and "HIV" interchangeably, and they often arrive with the fear that "if you get it, you die." The reality in 2026 is very different from the picture many people remember from campaigns 20–30 years ago. In this article I explain in simple terms what HIV is, how it differs from AIDS, how it is and is not spread, and the tools we have today for both prevention and treatment.

What is HIV?

HIV stands for human immunodeficiency virus. It is a virus that lives in and destroys a type of white blood cell called the CD4 T cell. These cells act like the "commanders" of the immune system. As more and more of them are destroyed, the body becomes less able to fight infections.

After infection, some people have flu-like symptoms in the first 2–4 weeks, such as fever, sore throat, rash and swollen lymph nodes. This is called acute HIV infection. But many people have no symptoms at all. After that comes a phase when a person can seem completely well for many years, while the virus is still slowly damaging the immune system. This is why a blood test is the only way to know. You cannot tell from symptoms or from how someone looks.

What is AIDS, and how is it different from HIV?

AIDS, or acquired immunodeficiency syndrome, is the late stage of HIV infection that has not been treated. The immune system has been damaged until it is very weak. Doctors usually use a CD4 count below 200 cells/mm³, or the appearance of opportunistic infections such as tuberculosis, fungal pneumonia or fungal meningitis, as the definition. (Read more in CD4 and opportunistic infections.)

1. 2–4 weeks
   Acute infection

   Some have fever, sore throat, rash, swollen glands; many have no symptoms

2. Several years
   Seemingly well

   No symptoms, but the virus slowly destroys CD4 cells; only blood tests reveal it

3. CD4 < 200
   AIDS

   Very weak immunity; opportunistic infections such as TB and fungal pneumonia

With early diagnosis and continuous treatment, most people never reach the AIDS stage.

How is HIV spread?

HIV is spread through certain body fluids that carry large amounts of virus: blood, semen and pre-ejaculate, vaginal fluids, rectal fluids and breast milk. The virus has to enter the body through a mucous membrane (such as the vagina, rectum or tip of the penis) or directly into the bloodstream. The main routes are:

1. Sex without protection, both vaginal and anal. Receptive anal sex carries the highest risk. Oral sex carries a very low risk, but it is still a route for other sexually transmitted infections.
2. Sharing needles or injecting equipment, including for injecting drugs.
3. From mother to baby during pregnancy, birth or breastfeeding, which today can be almost completely prevented.
4. Blood transfusions or organ transplants. In Thailand every unit of blood is now screened, so the risk is very low.

How HIV is not spread

This section is just as important as the one above, because misunderstanding is the root of the stigma and rejection people with HIV face. HIV is not spread by:

• Hugging, holding hands, a kiss on the cheek, or ordinary kissing
• Eating together, or sharing glasses, spoons or plates
• Sharing a toilet, swimming pool or bed
• Mosquitoes or other insect bites
• Sweat, tears or saliva (in everyday life)
• Living in the same house, working together, or caring for someone with HIV

And something many people still do not know: people with HIV who take antiretroviral treatment until the virus is undetectable in their blood do not pass HIV on through sex. This principle is called U=U (Undetectable = Untransmittable).

Can be spread

• Unprotected vaginal or anal sex
• Sharing needles or injecting equipment
• Mother to baby (almost entirely preventable)
• Blood or organ transfusion (Thailand screens every unit)

Cannot be spread

• Hugging, shaking hands, cheek kisses, ordinary kissing
• Sharing meals, glasses, spoons
• Toilets, swimming pools, mosquito bites
• Everyday sweat, tears, saliva

vs

People with HIV who take medicine until undetectable do not pass HIV on through sex (U=U).

How can HIV be prevented today?

Today we have much more than condoms. There are several layers of prevention to choose from, to fit each person's real life:

• Condoms with water-based or silicone lubricant prevent HIV and partly prevent other sexually transmitted infections. Lube helps reduce tears in the lining and lowers the chance of condom breakage.
• PrEP, medicine taken before a risk by people who do not have HIV but may be exposed. It can be taken daily, or on demand for some groups. (Read PrEP: HIV prevention before exposure.)
• PEP, medicine after a risk. It must be started as soon as possible, within 72 hours, and taken for 28 days. (Read PEP.)
• U=U: a partner with HIV who has stayed undetectable on treatment.
• Regular testing for people at risk, 1–4 times a year depending on behaviour, including HIV self-test kits.
• Not sharing needles or injecting equipment.

Can HIV be cured?

The honest answer is that it cannot yet be cured, but it can be controlled very well with antiretroviral therapy (ART). In Thailand the main regimen today is a single combination tablet taken once a day, with far fewer side effects than in the past. The World Health Organization (WHO) and Thailand's guidelines recommend starting treatment as soon as possible after diagnosis, without waiting for the CD4 count to fall. (Read HIV treatment and the TLD regimen.)

Thai nationals can receive antiretroviral treatment free of charge through the Universal Coverage Scheme, Social Security or the civil servant medical benefit scheme. Foreign residents and visitors usually receive treatment through private hospitals or clinics, or through their insurance. Data from large cohort studies in Europe and North America (ART-CC, 2023) found that people who start treatment and stay on it have a life expectancy that is getting closer and closer to that of the general population, especially those who start while their CD4 count is still high.

When to test, and how the clinic can help

Everyone should have an HIV test at least once in their life, and test again after sex without protection, a new partner, a past sexually transmitted infection, or sharing needles. If you had a risk within the last 72 hours, do not wait to test; ask about PEP first. (Read Just had an HIV exposure? What to do now.) To learn when a test result can be trusted, read Do you need to fast for an HIV test, and how reliable is a negative result?

At Dr. Kris Clinic in Surat Thani, I offer private, non-judgmental advice about HIV: from assessing your risk, testing for HIV and other sexually transmitted infections, and providing PrEP and PEP, to helping plan treatment and referring people who test positive into the right care system. Online consultations are available nationwide, and English-speaking consultations are available.