Tuberculosis and HIV

Tuberculosis and HIV are called "double trouble" because each infection makes the other more likely, more severe and harder to treat. HIV destroys the CD4 cells, the white blood cells that keep tuberculosis in check, and tuberculosis is often the illness that first reveals HIV. Good care depends on timing the right test, confirming the diagnosis, starting antiretroviral therapy early and preventing the infections that follow immune decline.

Dr. Neha Rastogi, Senior Consultant Infectious Diseases, Fortis Memorial Research Institute, Gurgaon, India, built her masterclass for primary care physicians across Africa around a series of clinic cases: the young man with a fever and a rash, the wife left untreated for twelve years, the resident with a needlestick injury, the patient whose therapy appeared to fail. Her starting point was that infections ignore borders. Epidemiology, host factors and ethnicity vary, but the infections themselves can occur anywhere. The session concentrated on HIV, with tuberculosis treated through its overlap with HIV, and a dedicated tuberculosis session was proposed for a later date.

This guide covers diagnosis, staging, transmission and counselling, within the wider work of the infectious diseases specialty. Two companion articles go deeper: antiretroviral regimens, treatment failure and tuberculosis co-infection, and HIV prevention through PrEP, PEP and the prevention of mother-to-child transmission. The questions doctors raised during the session are answered in the Live Discussion.

Why tuberculosis and HIV are called double trouble

Tuberculosis and HIV are double trouble because the presence of one is a risk factor for the other. Dr. Rastogi Panda framed the relationship in both directions. A patient with tuberculosis is more likely to be carrying HIV, and a patient with HIV is more likely to develop tuberculosis, in more varied forms and with more drug resistance. People living with HIV are about 16 times more likely to fall ill with tuberculosis than people without it, and tuberculosis remains the leading cause of death among people living with HIV.

The mechanism is immunological. HIV depletes the CD4 lymphocytes that normally contain Mycobacterium tuberculosis, so a latent infection can reactivate and a new one can progress quickly. The overlap then complicates every stage of care: the clinical presentation is less typical, the diagnosis is harder, and the treatment is constrained because rifampicin, the backbone of tuberculosis therapy, interacts with many antiretroviral drugs.

Both infections share three features that make them important for any front-line doctor. They are communicable. Their presentation is extremely varied: tuberculosis, in Dr. Rastogi Panda's words, can present in almost any organ and belongs in the differential diagnosis of almost any syndrome. And HIV carries a burden of myth, stigma and confusion about treatment that is, as she put it, more "viral" than the virus itself.

HIV infection is not the same as AIDS

The single most important message to give a newly diagnosed patient is that HIV infection is not AIDS. Dr. Rastogi Panda divides HIV infection into two forms, depending on when the patient first reaches the clinic:

• Acute infection, which resembles an acute viral illness such as influenza: high fever, sore throat, cough, cold, enlarged lymph nodes and marked weakness.
• Chronic infection, which, if left untreated, progresses to advanced HIV disease, the acquired immunodeficiency syndrome (AIDS).

The distinction matters most at the moment of counselling. Antiretroviral therapy (ART), started at any point after diagnosis, limits and halts progression to AIDS. Even in 2025, she noted, patients still arrive asking whether they can lead a normal life, whether HIV and AIDS are the same thing, and what HIV means for pregnancy. With modern therapy and the landmark trials in pre-exposure and post-exposure prophylaxis, the answer to each is far more reassuring than most patients expect.

The global burden of HIV

HIV remains concentrated in Africa and Asia. Dr. Rastogi Panda cited a figure of about 84.2 million people infected with HIV worldwide, which was the UNAIDS estimate of cumulative infections since the start of the epidemic at the end of 2021; eastern and southern Africa carries the largest share of people living with the virus. She pointed to the dense concentration of cases across the African continent, with Indian settings also carrying a substantial burden, which is why the same clinical questions arise in clinics on both continents.

The organising goal of HIV programmes is that people live with HIV rather than die of it. The UNAIDS 90-90-90 targets expressed this as three linked goals: 90% of people living with HIV know their status, 90% of those diagnosed receive sustained antiretroviral therapy, and 90% of those on therapy achieve viral suppression. The targets have since been raised to 95-95-95. Dr. Rastogi Panda emphasised the link between the second and third steps: access to therapy matters only if patients take it with consistent adherence.

Early signs of HIV: recognising acute infection

Acute HIV usually presents as a flu-like illness, and the diagnosis depends on thinking of it. Dr. Rastogi Panda's first case was a routine one: a sexually active man in his twenties with multiple partners, who presented with fever, lymphadenopathy (enlarged lymph nodes) and a generalised rash. The usual first thoughts are a viral infection, a streptococcal throat infection or an allergic reaction. HIV must sit on that differential list. Suspicion rests on two things together: a compatible clinical picture and, most of the time, an epidemiological link such as multiple sexual partners.

In the question session she listed the symptoms that most often bring patients with early HIV to a doctor:

• Intermittent fever over two to three months
• Fatigue and weakness
• Weight loss and loss of appetite
• Cough, cold and sore throat
• Falling ill more often than usual
• Loose stools or diarrhoea

The acute HIV syndrome itself, typically fever, sore throat, rash and enlarged lymph nodes, appears two to four weeks after infection and usually settles within one to two weeks; weight loss, diarrhoea and repeated illness over months point to more established infection. Recognising acute infection is valuable because the patient is at their most infectious when the viral load is highest.

How HIV is diagnosed: the testing window period

HIV is diagnosed with a viral load test from about the second week after infection, a p24 antigen test from two to four weeks and antibody tests after four weeks, and a positive result is confirmed with three different tests. Timing is the critical limiting factor: the right test ordered at the wrong time can miss the infection. Every HIV test has a window after infection during which it cannot yet detect the virus, and Dr. Rastogi Panda set out the sequence as a timeline:

1. The first two weeks. In practice, no test reliably detects infection in the first 14 days.
2. From the second week: viral load. A polymerase chain reaction (PCR) test detects viral RNA and measures the number of viral copies. It is the first test to turn positive.
3. From two to four weeks: p24 antigen. As the virus multiplies, it releases a core protein called p24 into the blood. The antigen can be picked up from about the second or third week, but it remains detectable only for around two weeks.
4. After four weeks: antibodies. Once the immune response develops, antibody tests detect the body's antibodies against HIV.

The practical rule follows directly: a test taken soon after an exposure reflects infection acquired some weeks earlier, not the exposure itself. This is why a negative result shortly after a needlestick injury or a high-risk sexual encounter does not exclude infection, and why repeat testing at the right interval matters. The same logic governs the timing of post-exposure prophylaxis, covered in the prevention article.

Confirming an HIV diagnosis: the three-test rule

A single positive test is never enough to label a patient HIV positive. Dr. Rastogi Panda stressed this because patients frequently arrive at the clinic holding one reactive result and asking whether they have HIV. The answer depends on a confirmatory algorithm, whether the patient is symptomatic (presenting with fever, tuberculosis or a fungal infection) or asymptomatic (testing after a sexual exposure).

In both scenarios, the diagnosis requires three different tests. They can differ in format (an ELISA, which is a laboratory antibody test, a rapid card test or a comb test) or in the antigens they use to detect HIV-1 and HIV-2 antibodies. The results are then read as a combination:

• All three tests reactive: the patient is HIV positive, and no further confirmation is needed.
• Two tests strongly reactive and one indeterminate: a viral load test helps decide. A positive viral load confirms the diagnosis; a negative one does not by itself exclude HIV, because a small minority of people with HIV, and anyone already taking antiretroviral drugs, can have an undetectable viral load, so the test sequence is repeated after about 14 days.

Only these two combinations lead to a diagnosis of HIV. The discipline protects patients from a life-changing label on the strength of a single false-positive result.

Opportunistic infections and WHO staging of HIV

Once HIV is confirmed, the next questions are how far the disease has progressed and which infections it has opened the door to. The World Health Organization (WHO) clinical staging system divides HIV into stages 1 to 4 according to the infections and conditions present, alongside CD4-based assessment. Opportunistic infections, the infections that take hold because the immune system is weakened, can be diagnosed at any stage.

Dr. Rastogi Panda gave common examples from newly diagnosed patients:

• Enlarged lymph nodes. Large nodes often raise fears of tuberculosis or lymphoma, but many turn out to be reactive persistent generalised lymphadenopathy, which is WHO stage 1.
• Oral thrush. Many patients arrive with oral candidiasis, a fungal infection of the mouth that is diagnosed clinically. WHO classifies persistent oral candidiasis as a stage 3 condition.
• Pulmonary tuberculosis. A patient diagnosed with tuberculosis who is then found to have HIV is already at WHO stage 3. A viral load in the hundreds of thousands of copies and a CD4 count below about 200 to 250 cells further stratify that patient's risk and prognosis.
• Cryptococcal meningitis. An AIDS-defining illness, diagnosed by testing the cerebrospinal fluid (CSF), or serum cryptococcal antigen when a CSF sample cannot be obtained.

Sometimes the opportunistic infection is what reveals the HIV in the first place. For diagnosis, Dr. Rastogi Panda uses a three-part model: the clinical symptoms and signs, the organ involved, and targeted sampling of that organ. In her patient with fever, cough and blood-stained sputum, a sputum sample tested with GeneXpert, a molecular test, confirmed tuberculosis.

The urine LAM test and stool testing

A doctor asked why the urine lipoarabinomannan (LAM) test, which detects a tuberculosis antigen in urine, is not used for every patient. Dr. Rastogi Panda explained that LAM reaches the urine only when the burden of tuberculosis bacilli is high and the CD4 count is low, and that the test was validated in patients with CD4 counts below 100. Its sensitivity and specificity rest on that population, so extending it to all patients is not supported. WHO recommends the test to support tuberculosis diagnosis in people living with HIV who have symptoms of tuberculosis, particularly those who are seriously ill or have advanced HIV disease, much as cryptococcal antigen testing is now used in the same group.

Stool testing for other opportunistic infections has a different limitation. In an untreated patient with a high viral load, the stool shows abundant normal flora and candida, which makes the results difficult to interpret for treatment decisions.

How HIV is and is not transmitted

HIV is transmitted mainly through unprotected sexual intercourse and through blood or blood products, not through everyday contact. In an HIV consultation, medical counselling is the smaller part; social counselling is the larger. Dr. Rastogi Panda described the questions patients bring: can the family eat from the same plate, can they sit in the same room, will sharing food pass the virus to the children, what about the spouse. None of these everyday contacts transmits HIV.

Beyond those two routes, she also advises male patients whose viral load is still high not to share razors, blades or other items that involve skin contact.

The most powerful message in counselling is U=U: undetectable equals untransmittable. A person living with HIV who maintains an undetectable viral load on antiretroviral therapy does not transmit HIV through sex. For young people who are about to marry or start a family, and who ask how they can lead a normal married life, this is the answer. The priority is the initial period of therapy, until the viral load reaches the undetectable mark. After that, a normal physical and emotional life is the realistic expectation.

HIV treatment and prevention after diagnosis

Two principles connect diagnosis to everything that follows.

First, everyone diagnosed with HIV should be treated, whatever the CD4 count. The modern regimen is usually a single daily pill combining two nucleoside reverse transcriptase inhibitors with an integrase inhibitor, but the choice of drugs must fit the whole patient: age, kidney and bone health, other medicines and pill burden. Therapy can also fail, often because of poor adherence, and a new infection such as tuberculosis can be the first sign of that failure. These decisions, together with second-line therapy and the prospects for a cure, are covered in HIV treatment: ART regimens, failure and TB co-infection.

Second, prevention now sits at the centre of HIV care. Pre-exposure prophylaxis protects HIV-negative partners and others at high risk, post-exposure prophylaxis protects people after a needlestick or sexual exposure, and antiretroviral therapy in pregnancy has made the elimination of mother-to-child transmission a realistic goal. Each is set out in HIV prevention: PrEP, PEP and mother-to-child transmission.

Dr. Rastogi Panda closed her lecture by reframing the acronym itself: HIV as hope and high cure rate, identify and investigate, and vigilant monitoring. With good therapy, a good doctor, good adherence and strong family support, she argued, a normal life with HIV is no longer a distant prospect.