How Does HIV Affect the Body: Stages and Organ Damage

HIV damages the body in stages, beginning with a burst of viral replication that strips immune cells from the gut lining and seeds reservoirs throughout the immune system, then settling into a years-long chronic phase where persistent inflammation quietly injures the heart, brain, kidneys, liver, lungs, and bones. Even when antiretroviral therapy suppresses the virus to undetectable levels, low-grade immune activation continues, and DNA-methylation studies indicate that people living with HIV are roughly five to seven years biologically older than their chronological age suggests. Understanding each stage and the organs it puts at risk helps explain why early treatment matters and why HIV care extends well beyond managing the virus itself.

The Acute Phase and the Gut as Ground Zero

Within days to weeks of infection, HIV replicates explosively. The virus has a strong preference for activated CD4 T cells, which are concentrated in the gut-associated lymphoid tissue. During this acute phase, the virus wipes out a massive share of CD4 cells in the intestinal mucosa. This early, severe mucosal depletion triggers a cascade: the tight junctions between cells lining the intestinal wall break down, enterocytes (the cells forming that barrier) die off, and the composition of gut bacteria shifts toward more harmful species.¹ The result is that bacteria and bacterial fragments leak through the damaged gut wall into the bloodstream, a process called microbial translocation.²

This leaky gut is not a temporary inconvenience. It becomes a sustained source of fuel for system-wide inflammation. Even people on effective antiretroviral therapy show elevated markers of microbial translocation, and this inflammation is now understood as a central driver of organ damage throughout the body.³ The destruction that begins in the gut during the first weeks of infection sets the stage for problems that play out over decades.

Chronic Inflammation and Why It Persists on Treatment

Once antiretroviral therapy drives the virus to undetectable levels in the blood, you might expect the immune system to calm down. It does, but not entirely. Chronic immune activation and inflammation remain one of the defining features of treated HIV, and they are strongly predictive of disease progression, organ damage, and death.⁴ Part of the reason is that latently infected cells survive indefinitely. When activated CD4 T cells become infected and then revert to a resting memory state, the viral DNA hides inside them, silenced but intact. Because memory T cells can live for decades, this reservoir persists even in patients on potent therapy.⁵

That hidden reservoir, combined with ongoing microbial translocation from the gut and immune cells that have become metabolically dysregulated and exhausted, keeps the inflammatory furnace lit at a low burn. Over time, this smoldering inflammation reaches virtually every organ system.

Cardiovascular Damage

Heart disease is one of the most studied complications of chronic HIV. The virus does not need to infect heart tissue directly; instead, persistent inflammation promotes arterial stiffness, plaque buildup, and structural changes to the heart. A comparative study in Tanzania found that HIV infection was independently associated with elevated arterial stiffness, and that this stiffness was in turn linked to echocardiographic changes including altered heart filling pressures and increased heart-muscle mass.⁶ Newer antiretroviral regimens, particularly those based on integrase inhibitors, have reduced the severe metabolic side effects of older drugs, but they come with their own concerns: these regimens are associated with weight gain and growth of specific fat deposits around the heart and blood vessels, which may independently contribute to cardiovascular risk.⁷

The Brain and Nervous System

HIV can enter the central nervous system during early infection, and once there, it establishes a separate compartment where the virus and its inflammatory effects are partially shielded from treatment. Persistent infection and inflammation in the brain contribute to a range of cognitive problems grouped under the term HIV-associated neurocognitive disorder, or HAND.⁸ In the era of effective antiretroviral therapy, the most severe form (HIV-associated dementia) has become far less common, but milder forms, including difficulty with concentration, memory, and processing speed, remain surprisingly prevalent. Many people living with HIV report feeling cognitively “off” even when their viral load is undetectable, and brain imaging studies show ongoing low-level inflammation that correlates with these complaints.

Kidney Disease

The kidneys are among the organs HIV can infect directly. The virus enters specialized kidney cells called podocytes and tubular epithelial cells, and the resulting damage can lead to a distinctive form of kidney disease known as HIV-associated nephropathy, or HIVAN.⁹ HIVAN classically appears in younger adults of African ancestry with advanced HIV disease, and this genetic link is now well understood: two risk variants in the APOL1 gene play a critical role in who develops the disease.¹⁰ Beyond HIVAN, HIV-related immune complex disease is the second most common kidney diagnosis found on biopsy, and chronic kidney disease in people with HIV is shaped by an interplay of viral factors, genetic susceptibility, and environmental exposures.¹¹

Liver and Metabolic Health

Nonalcoholic fatty liver disease has emerged as a major concern for people living with HIV. Depending on how it is measured, fatty liver disease occurs in roughly 30 to 65 percent of this population, driven by metabolic syndrome, abnormal fat distribution, the virus itself, some antiretroviral drugs, and changes to the gut microbiome.¹² An interesting twist is that fatty liver appears to progress faster in people with HIV alone than in those co-infected with HIV and hepatitis C, and in the HIV mono-infected group, fat accumulation in the liver was a strong predictor of progressing to liver fibrosis.¹³ Weight gain, which is common on modern antiretroviral regimens, independently predicts worsening fibrosis as well.¹⁴

The metabolic picture extends beyond the liver. Earlier antiretroviral regimens, particularly drugs like stavudine and zidovudine, caused a striking redistribution of body fat: subcutaneous fat wasted away while abdominal fat accumulated, a condition called lipodystrophy. This was accompanied by insulin resistance and unhealthy lipid profiles. The underlying metabolic disturbance involves accelerated breakdown of fat and increased repackaging of fatty acids in the liver.¹⁵ Newer drugs have largely eliminated the most severe forms of lipodystrophy, but the fat-related effects of older drugs do not always reverse after switching, and current regimens bring weight gain with their own metabolic consequences.⁷

Lung Disease Beyond Infections

In the early years of the epidemic, lung disease in HIV meant pneumonia. That has changed. While opportunistic lung infections still occur in people with severely suppressed immune systems, noninfectious lung conditions have become common complications. HIV infection increases the risk of chronic obstructive pulmonary disease (COPD), emphysema, lung fibrosis, and pulmonary arterial hypertension.¹⁶ A large study using French hospital data showed that even among younger adults (ages 30 to 49), HIV infection was independently associated with these conditions after accounting for smoking.¹⁷ COPD in particular is frequent enough in the HIV population to warrant active screening and management.¹⁸

Bone Loss

Bone mineral density tends to be lower in people with HIV than in the general population, and this difference holds up even after adjusting for age, weight, race, and other confounders. In a study of men with or at risk for HIV, bone density at both the hip and lower spine was significantly reduced in HIV-positive participants compared to HIV-negative controls.¹⁹ Most of the bone loss appears to happen during two windows: while the virus is actively replicating (before treatment) and during the first months after starting antiretroviral therapy, when the recovering immune system ramps up the activity of cells that break down bone.²⁰ Some antiretroviral classes, including protease inhibitors and certain backbone drugs, have been linked to additional bone loss, making the problem multifactorial: the virus, the immune recovery, the drugs, and traditional risk factors like smoking and vitamin D deficiency all play a role.²¹

Blood Cell Production

HIV affects the bone marrow, where all blood cells are produced. Disruption of the bone marrow niche, through both direct and indirect effects of the virus, contributes to the low blood counts seen in many HIV patients.²² This can show up as anemia, low platelet counts, or low white blood cell counts. In severe cases, HIV-related bone marrow suppression can lead to pancytopenia, where all three cell lines are depleted.²³ These blood abnormalities can complicate diagnosis and treatment, especially when the underlying HIV infection is not yet recognized.

Skin as an Early Warning System

Skin problems are among the most visible signs of HIV-related immune suppression. Papular pruritic eruption, the most common HIV-specific skin condition, produces intensely itchy bumps on the limbs, trunk, and sometimes face. The itch and severity worsen as CD4 counts drop. Xerosis, or severe dry skin, results from damage to the skin’s barrier function, with changes in lipid content in the outer skin layers. It is a major cause of premature skin aging in people with HIV. Eosinophilic folliculitis, an inflammatory eruption around hair follicles, is most common at lower CD4 counts and is thought to involve an exaggerated immune response to antigens in the oil glands.²⁴ Because these conditions tend to track with immune status, their appearance or worsening can serve as a clinical signal that the virus is not being adequately controlled.

When the Immune System Collapses

Without treatment, the CD4 count eventually falls below 200 cells per cubic millimeter, the threshold that defines AIDS. At this point, infections that a healthy immune system would easily contain become life-threatening. Pneumocystis pneumonia, toxoplasmosis, and Mycobacterium avium complex infections all surge in frequency once CD4 counts drop below 200. At counts below 50, the risks expand further to include cytomegalovirus retinitis, central nervous system lymphoma, and disseminated fungal infections.²⁵ In one study, circulating CD4 counts were below 200 before 46 out of 49 episodes of Pneumocystis pneumonia, all 8 episodes of cytomegalovirus pneumonia, and all 7 episodes of Cryptococcus infection.²⁶

These opportunistic infections are not just markers of immune collapse; they cause their own organ damage. Toxoplasmosis creates brain abscesses. Cytomegalovirus can destroy the retina, colon, or adrenal glands. Mycobacterium avium complex can infiltrate the liver, bone marrow, and lymph nodes. The cascade of infections compounds the organ damage the virus has already been quietly causing through inflammation.

The Paradox of Immune Recovery

Starting antiretroviral therapy when CD4 counts are very low introduces another risk. As the immune system rebuilds, a small subset of patients experience immune reconstitution inflammatory syndrome, or IRIS, where the recovering immune system mounts an excessively aggressive response against infections that were already present, whether the person knew about them or not.²⁷ Symptoms can range from swollen lymph nodes and fever to worsening of tuberculosis, fungal infections, or viral conditions. The underlying problem appears to be an imbalance: effector immune cells bounce back faster than the regulatory cells that keep them in check, leading to an overblown inflammatory response.²⁸ IRIS is manageable in most cases, but it reinforces the point that starting treatment earlier, before the immune system is severely depleted, avoids some of the most dangerous complications.

Why Starting Treatment Early Protects Organs

The evidence for early antiretroviral therapy extends beyond suppressing the virus. In the landmark START trial, which randomized people with high CD4 counts to begin treatment immediately or wait, those who started early had a lower rate of new AIDS events and tuberculosis.²⁹ A liver-specific analysis of START showed that immediate treatment reduced the risk of developing liver fibrosis by about a third compared to deferred treatment, and was also more likely to reverse elevated fibrosis scores that were already present at baseline.³⁰ Long-term cardiovascular follow-up of the same trial, over a median of about nine years, did not find a clear overall difference in heart disease events between the early and deferred groups, though there was a possible benefit of early therapy in women.³¹ The takeaway is that early treatment’s organ-protecting benefits are real, but they vary by organ and possibly by sex.

Accelerated Biological Aging

One of the more striking findings in recent HIV research is that the virus appears to accelerate biological aging at the molecular level. Epigenetic clocks, which estimate biological age based on chemical modifications to DNA, show that people living with HIV are on average five to seven years biologically older than HIV-negative people of the same chronological age.³² This acceleration shows up in both blood and brain tissue, with brain tissue aging even faster, by an average of about seven years.³³ The mechanisms feeding this aging include persistent viral activity, chronic immune activation, mitochondrial dysfunction, oxidative stress, and treatment-related metabolic effects.³⁴

This accelerated aging helps explain why people with HIV develop conditions like heart disease, kidney failure, osteoporosis, and cognitive decline at younger ages than their HIV-negative peers. It also means that standard age-based screening guidelines for these conditions may not be aggressive enough for people living with HIV.

Cancer Risk

HIV increases the risk of certain cancers through several overlapping routes: the direct oncogenic effects of the virus, immunosuppression that allows cancer-promoting viruses (like human papillomavirus and Epstein-Barr virus) to thrive, chronic inflammation, and higher rates of traditional cancer risk factors like smoking among people with HIV.³⁵ AIDS-defining cancers like Kaposi sarcoma and certain lymphomas have declined dramatically with effective treatment, but non-AIDS-defining cancers, including lung, liver, and anal cancers, have become a growing concern as people with HIV live longer.

Clonal Hematopoiesis and Emerging Risks

A newer area of research involves clonal hematopoiesis, a condition where blood stem cells acquire mutations that give them a growth advantage, causing them to produce a disproportionate share of your blood cells. In the general population, clonal hematopoiesis becomes more common with age and is linked to an increased risk of blood cancers and cardiovascular disease. In people with HIV, even those on effective treatment, the residual chronic inflammation appears to create a favorable environment for these mutant clones to expand.³⁶ Multiple mechanisms likely contribute: immunodeficiency, higher rates of smoking, and the chronic antigenic stimulation that defines treated HIV may all modify the competitive landscape in the bone marrow.³⁷ Data from the REPRIEVE cardiovascular prevention trial in people with HIV further support the hypothesis that residual inflammation, acting through tumor suppressor and inflammasome pathways, drives high rates of clonal hematopoiesis in this population.³⁸ The clinical significance of this is still being worked out, but it may partly explain the elevated cardiovascular and cancer risks that persist even in virally suppressed individuals.