World AIDS Day 2025: Doctor explains how HIV affects the immune system, why prevention is important

HIV doesn’t just spread — it gradually dismantles the immune system from within. On World AIDS Day, here’s a doctor-explained breakdown of what really happens inside the body

HIV (Human Immunodeficiency Virus) Is a virus that attacks the bodies immune system, especially the cells that help fight infections. If untreated, it can weaken the immune system and cause more serious illness. Today, December 1, is World AIDS Day, an important day to raise awareness and work a future without stigma.

Discussions about HIV were, in the past,  centred on how the virus spreads and how one might keep it at bay. However, today experts say that understanding what HIV actually does inside the body is essential because early awareness leads to early care, and that changes everything

According to Dr Swapnil Gautam, Infectious disease physician Bombay Hospital, Mumbai HIV’s first target is the CD4+ T-cell, an important part of the immune response. “These cells help the body recognise and attack unwelcome invaders. Once inside the bloodstream, HIV attaches itself to these cells, fuses with them, and injects its genetic code.” he tells Moneycontrol, adding, “The virus essentially hijacks the cell and forces it to produce more copies of itself, When each invaded CD4 cell finally collapses, thousands of new virus particles spill out, ready to infect again.”

Also Read: All about HIV infection: Causes, symptoms and treatment strategies

Just two to six weeks after exposure comes the acute infection phase. He said, “It looks and feels suspiciously like a bout of flu, fever, fatigue, a sore throat, swollen glands. But beneath that seemingly common illness, is HIV.” CD4 counts dip and viral load skyrockets. Then, without warning, the virus slips into a chronic phase. One can feel perfectly fine for years. But HIV never stops working. It hides in lymph nodes and tissues, steadily chipping away at the immune system. “People often don’t realise their body is under strain until opportunistic infections appear,” Dr Gautam informs.

During this latent stage, the  CD4 cells are lost faster than the body can replace them. Though outwardly healthy, a person’s immune system is slowly weakening. Dr Gautam shares that if left untreated, the long decline leads to AIDS. "At this point, everyday infections become dangerous. Tuberculosis, pneumonia, fungal infections, and even certain cancers gain the upper hand because the immune system can no longer defend itself", says Dr Gautam.

Today’s antiretroviral therapy (ART) has transformed the narrative. “ART stops the virus from multiplying and allows the immune system to rebuild,” says Dr Gautam. When taken consistently, ART suppresses HIV to undetectable levels, which means it cannot be sexually transmitted. As CD4 levels rise, people on treatment can enjoy long, productive lives. HIV becomes a manageable chronic condition rather than a sentence of decline. "The more we understand the inside of the body, the better equipped we are to dispel stigma, encourage testing, and ensure that those living with HIV receive the care and dignity they deserve", he adds.

Also Read: World Aids Day 2024: Prevent HIV, follow these critical tips for safer sex, healthier life

FAQs on HIV:

1. What is HIV?

HIV stands for Human Immunodeficiency Virus, which attacks the body's immune system, specifically the CD4+ T-cells.

2. How does HIV affect the body?

HIV attaches itself to CD4+ T-cells, hijacking them to reproduce and eventually destroying them, leading to a weakened immune system.

3. What are the early symptoms of HIV?

Early symptoms can mimic flu-like symptoms, including fever, fatigue, sore throat, and swollen glands.

4. How is HIV detected?

HIV is detected through blood tests that check for the presence of the virus or the body's response to the virus.

5. What happens if HIV is left untreated?

If left untreated, HIV can progress to AIDS, where the immune system is severely weakened, making the body susceptible to opportunistic infections and certain cancers.

Disclaimer: This article, including health and fitness advice, only provides generic information. Don’t treat it as a substitute for qualified medical opinion. Always consult a specialist for specific health diagnosis.