People at highest risk for tuberculosis fall into two groups: those more likely to be exposed to TB bacteria in the first place, and those whose immune systems are less able to keep an infection from becoming active disease. Most people who breathe in TB bacteria never get sick. About 5% of otherwise healthy adults develop active TB within two years of infection, and after that the annual risk drops sharply. But certain medical conditions, medications, living situations, and lifestyle factors can dramatically shift those odds.
HIV and Weakened Immune Systems
HIV is the single strongest medical risk factor for tuberculosis. People living with HIV are 18 times more likely to develop active TB than people without HIV, and TB remains the leading cause of death among this group. In 2019, roughly 30% of AIDS-related deaths worldwide were caused by TB. Even people on antiretroviral therapy who develop TB are three times more likely to die during treatment than HIV-negative TB patients.
Other forms of immune suppression carry similar dangers. Organ transplant recipients taking anti-rejection drugs, people on long-term corticosteroids, and anyone receiving cancer chemotherapy have a reduced ability to contain TB bacteria after exposure. The immune system normally walls off TB germs inside tiny clusters of cells called granulomas. When immune function drops, those walls can break down, allowing a dormant infection to become active disease months or even years later.
Medications That Suppress Immune Defenses
A class of drugs used to treat rheumatoid arthritis, Crohn’s disease, and other inflammatory conditions poses a specific TB risk. These medications work by blocking a signaling molecule that plays a central role in inflammation, but that same molecule is essential for maintaining the granulomas that keep latent TB contained. When patients start these drugs, there is a temporary but significant spike in the risk of TB reactivation because the granuloma structure weakens and the body’s ability to produce key infection-fighting signals drops sharply. Doctors typically screen for latent TB before prescribing these medications for exactly this reason.
Diabetes
Diabetes was the most commonly reported medical risk factor among people diagnosed with active TB in the United States in 2023. Nearly 1 in 4 people diagnosed with TB disease also has diabetes. The connection runs in both directions: high blood sugar impairs the immune cells responsible for detecting and killing TB bacteria, and TB infection can worsen blood sugar control. Someone with untreated latent TB and diabetes is more likely to progress to active disease than someone with latent TB alone.
Children Under Five
Babies and young children have immature immune systems that struggle to contain TB bacteria after exposure. Children under five are not only more likely to develop active disease once infected, they are also more vulnerable to the most dangerous forms, including TB that spreads to the brain (TB meningitis) or throughout the bloodstream. This is why many countries with high TB rates vaccinate infants with BCG, a vaccine that specifically protects against these severe forms of childhood TB.
Smoking and Heavy Alcohol Use
Smoking increases TB risk far more than most people realize. Among people without a history of TB, smokers are nine times more likely to die from the disease than those who have never smoked. Children exposed to secondhand smoke in a household with a TB patient are more than five times as likely to develop active disease. The good news: quitting smoking cuts TB death risk by about 65% compared to continuing.
Heavy alcohol use, generally defined as two or more drinks per day, carries its own independent risk. A long-term study in New York City found that people with alcohol use disorders developed TB at nine times the rate of the age-matched general population. A large pooled analysis across multiple studies estimated that heavy drinkers have roughly 3.5 times the risk of active TB. Alcohol also makes treatment harder to complete. People with alcohol use disorders are about twice as likely to default on TB treatment and nearly four times as likely to relapse after finishing it.
When smoking and heavy drinking overlap, the combined effect is worse than either alone.
Living in Congregate Settings
TB spreads through the air, so anywhere people live in close quarters for extended periods creates transmission risk. The WHO identifies several specific environments:
- Prisons and jails, where overcrowding and poor ventilation are common
- Homeless shelters, where people cycle in and out and may have other risk factors like substance use or HIV
- Refugee camps, where large populations share limited space
- Nursing homes and long-term care facilities, where residents are often elderly and immunocompromised
- Military barracks, dormitories, and mining compounds, where shared sleeping quarters increase airborne exposure
The common thread is prolonged, close-proximity contact in enclosed spaces with limited airflow. A single undiagnosed case of active TB in any of these settings can expose dozens or hundreds of people before it is identified.
Healthcare Workers
Healthcare workers face occupational exposure to TB, particularly in emergency departments, pulmonary clinics, and facilities that perform procedures generating airborne particles like sputum collection or bronchoscopy. In facilities without strong infection control measures, some studies have found the occupational risk to be five to nine times higher than in the surrounding community. However, in hospitals that follow modern infection control guidelines, the risk for healthcare workers generally approaches the same level as the community they live in. The CDC recommends baseline TB screening for all healthcare personnel, with repeat testing after known unprotected exposure to an active TB case.
People Born in or Traveling to High-Burden Countries
Geography is one of the strongest predictors of TB exposure. The WHO designates 30 countries as high TB burden for 2021 through 2025, and these nations accounted for 87% of the estimated 10.3 million new TB cases in 2023. The list includes India, Indonesia, China, the Philippines, Pakistan, Nigeria, Bangladesh, South Africa, Ethiopia, Myanmar, and 20 others spanning sub-Saharan Africa, Southeast Asia, and parts of South America and Eastern Europe.
In the United States, the CDC considers anyone who has lived for at least one month in a country with a high TB rate to be at increased risk. This applies broadly to anyone born outside of the U.S., Canada, Australia, New Zealand, and western or northern Europe. Many TB cases diagnosed in low-incidence countries trace back to infections acquired years or decades earlier in a high-burden setting, reactivating long after the person has moved.
How These Risk Factors Overlap
TB risk rarely exists in isolation. A person living with HIV in a high-burden country faces compounding risks from immune suppression and frequent exposure. A homeless individual who smokes and drinks heavily may cycle through shelters where transmission is more likely, while also having a weakened ability to fight infection. Diabetes is rising rapidly in many of the same countries where TB is most common, creating an expanding overlap between two epidemics. Understanding which categories you fall into helps determine whether TB screening makes sense, even if you feel perfectly healthy.