Tuberculosis (TB) is an infectious disease caused by a type of bacteria, primarily affecting the lungs but capable of impacting other body parts. This illness continues to be a global health concern, making it important to understand which individuals face a higher likelihood of infection and progression to active disease. Identifying these risk factors helps in targeted prevention and treatment strategies worldwide.
Individuals with Compromised Immunity
A weakened immune system significantly increases the risk of developing active TB disease once infected with the bacteria. Various medical conditions and treatments can suppress the body’s natural defenses, leaving individuals more susceptible to both initial infection and progression from latent to active illness.
People living with HIV/AIDS are particularly vulnerable, as HIV directly attacks immune cells, rendering the body less able to fight off infections like TB. Individuals with HIV are estimated to be 14 to 18 times more likely to develop active TB disease than those without HIV, and TB is a leading cause of death among people with HIV. Similarly, diabetes impairs immune function, and it is estimated to contribute to a substantial number of new TB cases globally.
Other conditions and treatments that weaken the immune system include:
Severe kidney disease
Certain cancers, such as leukemia, lymphoma, and head and neck cancers
Treatments that suppress the immune system, including chemotherapy, long-term corticosteroids, or organ transplant rejection medications
Autoimmune conditions like rheumatoid arthritis or Crohn’s disease, especially when treated with immunosuppressive drugs
Malnutrition or low body weight, which compromises the immune system’s ability to respond effectively to pathogens
Close Contact and Environmental Factors
Direct exposure to individuals with active TB and certain environmental conditions play a substantial role in the transmission of the disease. Tuberculosis spreads through the air when an infected person coughs, sneezes, or sings, releasing tiny droplets containing the bacteria. Anyone nearby can then breathe in these droplets and become infected.
Prolonged or frequent close contact with someone who has active TB, especially within a household, significantly increases the risk of infection for family members, friends, or coworkers. The infectiousness of the source individual and the duration of contact are key determinants of transmission risk.
Crowded living conditions, such as shared dormitories, multi-family housing, or urbanized areas, facilitate the spread of TB bacteria. Poor ventilation in these spaces allows airborne bacteria to linger, increasing the likelihood of transmission. Socioeconomic factors like poverty and homelessness are often linked to these crowded and inadequate housing situations, as well as limited access to healthcare, all of which contribute to a higher overall risk of TB.
Specific Population and Geographic Risk Factors
Beyond individual health and immediate surroundings, broader demographic patterns, occupations, and geographic locations contribute to tuberculosis risk. Certain regions worldwide have a higher prevalence of TB, including parts of Africa, Asia, and Eastern Europe. Individuals residing in or traveling to these areas face an elevated risk of exposure to the TB bacteria, reflecting global disparities in disease burden.
Specific occupations also carry an increased risk of TB exposure. Healthcare workers, laboratory personnel, and others who regularly interact with TB patients or handle samples are more likely to encounter the bacteria. Congregate settings like correctional facilities, homeless shelters, and long-term care facilities present a higher risk due to the close proximity of individuals and the potential for delayed diagnosis and treatment. These environments facilitate easier transmission of the disease.
Migration patterns also influence TB risk, particularly for immigrants and refugees from countries with high TB burdens, who may have been exposed to the bacteria in their home countries. Age also plays a role in vulnerability; very young children (under five) have developing immune systems, making them more susceptible to TB infection and severe forms of the disease. Conversely, older adults (65 and above) face an increased risk due to a naturally weakening immune system over time.