People with weakened immune systems, particularly those living with HIV, face the highest risk of developing active tuberculosis. But TB risk isn’t determined by a single factor. It depends on a combination of immune health, living conditions, geography, age, occupation, and everyday habits like smoking and drinking. Globally, 10.7 million people developed TB in 2024, and the vast majority of cases cluster in populations where several of these risk factors overlap.
HIV and Immune System Conditions
HIV is the single strongest individual risk factor for tuberculosis. People living with HIV are 19 times more likely to develop active TB than people without HIV. The reason is straightforward: TB bacteria can live dormant in the body for years, kept in check by a healthy immune system. HIV destroys the specific immune cells responsible for that containment, allowing dormant TB to wake up and cause disease.
Other conditions that suppress the immune system carry similar, though generally lower, risks. Cancer, especially blood cancers and those treated with chemotherapy, reduces the body’s ability to fight TB. Organ transplant recipients take anti-rejection medications that deliberately weaken immune responses, which also opens the door to TB reactivation. People who have been infected with TB bacteria within the past two years are also at elevated risk, because the immune system hasn’t yet fully walled off the infection.
Biologic Medications
A specific class of drugs used for autoimmune conditions like rheumatoid arthritis and Crohn’s disease significantly raises TB risk. These medications work by blocking a protein called TNF-alpha, which plays a key role in keeping TB bacteria contained in the lungs. Antibody-type versions of these drugs carry a several-fold greater risk of TB reactivation compared to receptor-type versions, because of differences in how deeply they penetrate tissue and how tightly they bind. This is why doctors screen for latent TB before starting these treatments.
Diabetes
Diabetes roughly doubles your risk of developing active TB. A large Cochrane review covering more than 44 million participants found that people with diabetes were about 1.5 to 2.4 times more likely to develop TB disease than the general population. The connection goes beyond just getting sick: diabetes is also linked to higher death rates during TB treatment, greater chances of relapse after completing treatment, and increased likelihood of drug-resistant TB. As diabetes rates climb worldwide, particularly in countries that already have high TB burdens, this overlap is becoming a major public health concern.
Smoking and Alcohol Use
Current smokers face roughly twice the risk of developing active TB compared to people who have never smoked. Heavy alcohol use raises the risk even more, approximately threefold. When both habits combine, the numbers get worse: smokers who consume two or more alcoholic drinks per day have a risk more than three times higher than nonsmoking nondrinkers. Smoking damages the airways and impairs the lung’s local immune defenses, making it easier for TB bacteria to establish infection. Alcohol suppresses immune function more broadly and is often linked to poor nutrition, which compounds the problem further.
Overcrowding and Homelessness
TB spreads through the air, so the amount of time you spend breathing shared air with an infected person matters enormously. Overcrowded housing, generally defined as more than two people per room, is one of the strongest environmental risk factors for TB transmission. Crowded conditions directly increase exposure, and they tend to come packaged with other problems: poor ventilation, dampness, and limited sunlight, all of which help TB bacteria survive longer in the air. Research has even found that people living on lower floors of dense high-rise buildings face higher TB risk due to reduced airflow and sunlight.
Homelessness amplifies every one of these factors. TB incidence among homeless populations is about 10 times higher than in the general population. The rate of latent TB infection among homeless people is roughly five times higher than among those with stable housing. Treatment is also harder to complete: homeless individuals are twice as likely to not finish their TB treatment course, and homelessness increases the risk of TB recurring after treatment.
Prisons and jails pose similar risks. Correctional facilities combine overcrowding, poor ventilation, high stress, and populations that often have underlying health conditions, making them persistent hotspots for TB transmission.
Where You Live or Were Born
Geography is one of the most reliable predictors of TB risk. Thirty high-burden countries account for 87% of all TB cases worldwide. The top 20 countries by total case numbers include India, Indonesia, China, Bangladesh, Ethiopia, the Democratic Republic of the Congo, Kenya, Brazil, Angola, and North Korea, among others. Many countries in sub-Saharan Africa, South and Southeast Asia, and parts of Latin America carry substantially higher TB rates than North America or Western Europe.
If you were born in or frequently travel to these regions, your lifetime risk of TB exposure is significantly higher. This is why the CDC recommends TB testing for people born in or who regularly visit countries where TB is common, regardless of whether they have symptoms.
Infants and Young Children
Children under five are uniquely vulnerable to TB. Once infected, young children are more likely than older children or adults to progress quickly from infection to active disease. Their immune systems haven’t fully matured, which means they’re less able to contain TB bacteria after exposure. Infants and toddlers are also more likely to develop the most dangerous forms of TB, including TB meningitis (infection of the brain and spinal cord lining) and miliary TB, where the bacteria spread to multiple organs throughout the body. These severe forms carry high rates of death and lasting disability, which is why the BCG vaccine is given to infants in countries where TB is common.
Healthcare Workers
People who work in hospitals, clinics, homeless shelters, correctional facilities, and nursing homes face repeated TB exposure that most people never encounter. A large study comparing healthcare workers to educational workers found that healthcare workers with evidence of TB infection were more than twice as likely to develop active TB disease. Even healthcare workers who tested negative for TB infection still had a 76% higher risk than educational workers who also tested negative, suggesting that ongoing occupational exposure creates a cumulative risk that standard screening doesn’t always capture.
In high-burden countries, where infection control resources are often limited, healthcare workers face some of the highest occupational TB rates of any profession. The incidence among those with untreated latent TB reached 245.5 per 100,000 in one study, far above the rate in comparable non-healthcare occupations.
When Multiple Risk Factors Overlap
TB risk rarely comes from a single source. A person living with HIV in a high-burden country who also smokes faces a dramatically compounded risk compared to someone with only one of those factors. Similarly, a homeless person with diabetes in an overcrowded shelter is dealing with layered vulnerabilities: immune impairment, constant exposure, and barriers to treatment all at once.
The CDC recommends TB testing for anyone who falls into one or more higher-risk categories: people born in or traveling to high-burden countries, those living or working in group settings like shelters or correctional facilities, people with HIV or diabetes, anyone taking immune-suppressing medications, children under five, people who inject drugs, and those who have been recently exposed to someone with active TB disease. Testing is generally not recommended for people at low risk, since false positives become more likely when the actual chance of infection is small.