What Is Tuberculosis?
Tuberculosis, commonly known as TB, is a bacterial infection caused by Mycobacterium tuberculosis that primarily attacks the lungs but can also affect the kidneys, spine, brain, and other parts of the body. It remains one of the top 10 causes of death worldwide and the leading cause of death from a single infectious agent, surpassing even HIV/AIDS. The World Health Organization estimates that roughly one-quarter of the global population carries latent TB infection.
TB bacteria spread through the air when a person with active pulmonary TB coughs, sneezes, speaks, or sings. Nearby individuals can inhale these airborne droplet nuclei, which are small enough to reach the deep airways of the lungs. Importantly, TB is not spread by shaking hands, sharing food or drink, touching bed linens, or sitting on toilet seats. Prolonged close contact in enclosed spaces significantly increases transmission risk.
Latent TB vs. Active TB
Understanding the distinction between latent and active TB is essential for travelers. In latent TB infection, the bacteria remain in the body in an inactive state, causing no symptoms and posing no risk of transmission. The person is not sick and cannot spread TB to others. However, without treatment, latent TB can progress to active TB disease at any point, with the highest risk occurring within the first two years after initial infection.
- Latent TB: No symptoms, not contagious, positive skin test or blood test, normal chest X-ray, needs preventive treatment to eliminate the bacteria
- Active TB: Symptomatic, contagious if in the lungs, positive skin test or blood test, abnormal chest X-ray or positive sputum smear, requires immediate multi-drug treatment
Symptoms of Active TB
- A persistent cough lasting three weeks or longer, sometimes producing blood-tinged sputum
- Chest pain and difficulty breathing
- Unexplained weight loss and loss of appetite
- Night sweats and fever, often low-grade
- Extreme fatigue and weakness
- Chills and body aches
Risk for International Travelers
The risk of contracting TB during short-term travel is generally low for most tourists. However, the risk increases significantly for travelers who spend extended periods in countries with high TB prevalence, particularly those who work or volunteer in healthcare settings, prisons, homeless shelters, or refugee camps. Backpackers staying in crowded hostels and travelers visiting friends and family in high-burden countries also face elevated risk.
High-Prevalence Regions
- Southeast Asia: India, Indonesia, the Philippines, and Myanmar account for the largest share of global TB cases
- Sub-Saharan Africa: South Africa, Nigeria, the Democratic Republic of Congo, and Mozambique have particularly high rates, often complicated by HIV co-infection
- Eastern Europe and Central Asia: Russia, Ukraine, and several Central Asian republics report elevated rates, including drug-resistant strains
- Western Pacific: China and Vietnam remain significant contributors to global case counts
Testing After Travel
Travelers who have spent prolonged time in high-prevalence countries should undergo TB screening 8 to 10 weeks after returning home. This window allows enough time for the immune system to develop a detectable response to the bacteria. Two main testing methods are available.
- Tuberculin skin test (TST or Mantoux test): A small amount of purified protein derivative is injected under the skin of the forearm, and the injection site is examined 48-72 hours later for a raised, hardened area indicating infection
- Interferon-gamma release assay (IGRA): A blood test that measures the immune response to TB proteins; results are available within 24 hours and are not affected by prior BCG vaccination
- If either test is positive, a chest X-ray and possibly sputum samples will be ordered to determine whether the infection is latent or active
Treatment Options
Treatment for latent TB typically involves a course of one or two antibiotics taken for 3 to 9 months, depending on the regimen chosen. Completing the full course is critical to preventing progression to active disease. For active TB, the standard treatment involves a combination of four antibiotics -- isoniazid, rifampicin, ethambutol, and pyrazinamide -- taken for an initial intensive phase of two months, followed by a continuation phase of four months with isoniazid and rifampicin.
Drug-resistant TB poses a growing global concern. Multidrug-resistant TB (MDR-TB) does not respond to at least isoniazid and rifampicin, the two most powerful first-line drugs. Treatment for MDR-TB requires second-line medications that are more expensive, have more side effects, and must be taken for 9 to 20 months. Extensively drug-resistant TB (XDR-TB) is resistant to even more drugs and is particularly difficult to treat, sometimes requiring experimental therapies. Travelers should be aware that drug-resistant strains are particularly prevalent in parts of Eastern Europe, Central Asia, and southern Africa.
The BCG Vaccine
The Bacillus Calmette-Guerin (BCG) vaccine is the only available vaccine against tuberculosis and has been in use since 1921, making it one of the most widely administered vaccines in history. BCG is routinely given to infants and children in countries with high TB prevalence but is not commonly used in countries like the United States, where TB rates are low. The vaccine provides moderate protection against severe forms of childhood TB, including TB meningitis, but its effectiveness against adult pulmonary TB varies widely, ranging from 0% to 80% depending on the population studied. Travelers who did not receive BCG as children should discuss the vaccine with a travel medicine specialist if they plan extended stays in high-prevalence countries, particularly if they will be working in healthcare, corrections, or refugee assistance settings.
BCG and TB Testing
One important consideration for travelers who have received the BCG vaccine is that it can cause a false-positive result on the tuberculin skin test (TST). This means the skin test may indicate TB infection when the person is actually just reacting to the vaccine. For this reason, the interferon-gamma release assay (IGRA) blood test is preferred for individuals with a history of BCG vaccination, as it is not affected by prior vaccination and provides a more accurate result. Always inform your healthcare provider about your BCG vaccination history before undergoing TB screening.
Prevention Tips for Travelers
- Avoid prolonged time in crowded, poorly ventilated indoor spaces in high-prevalence countries, especially public transportation, shelters, and healthcare waiting areas
- If volunteering or working in healthcare settings abroad, follow infection control protocols including wearing N95 respirator masks when in contact with potential TB patients
- Maintain a strong immune system through adequate nutrition, sleep, and stress management, as a weakened immune system increases susceptibility to infection
- If staying abroad for more than three months, schedule TB screening both before departure and 8 to 10 weeks after returning home
- Travelers living with HIV or other immunocompromising conditions should consult with their physician before traveling to high-prevalence areas, as they face significantly higher risk of both infection and progression to active disease