Tuberculosis (TB) is a contagious disease that often affects the lungs. It is caused by bacteria called Mycobacterium tuberculosis. Every year there are about nine million cases worldwide. If you are planning to travel abroad, how can you reduce your risk of TB?

What Is the Risk to Travelers?

If you are an international traveler, you may be at an increased risk for contracting TB because:

• You may be visiting countries where TB is prevalent.
• Your mode of transportation is a confined area (such as an airplane), where you may share air space with someone who has active TB.

The World Health Organization lists profiles for the 22 high burden countries that account for 80% of all new TB cases each year. The countries are:

• India
• China
• Indonesia
• Nigeria
• South Africa
• Bangladesh
• Ethiopia
• Pakistan
• Philippines
• Democratic Republic of Congo
• Afghanistan
• Brazil
• Cambodia
• Kenya
• Mozambique
• Myanmar
• Russian Federation
• Thailand
• Uganda
• United Republic of Tanzania
• Vietnam
• Zimbabwe

How Is TB Transmitted?

When someone with active TB coughs, the bacteria are transmitted through the air and may be inhaled by people nearby. TB is more likely to spread from person-to-person in enclosed places because:

• Water droplets carrying the bacteria are more widely dispersed outdoors
• Ultraviolet radiation from the sun kills TB

Fortunately, exposure to TB bacteria does not automatically mean the disease will develop. If you have a normal immune system, your body's defenses will immediately build a "fortress" around the bacteria. This may keep TB dormant in your body for years, possibly a lifetime. If the bacteria remain inactive, a person is considered infected, but does not have active tuberculosis and cannot infect others.

TB becomes active and symptomatic when the immune system's fortress can no longer contain the growth of the bacteria. Usually, this happens when the immune system is weakened, due to certain conditions, such as poorly controlled diabetes, HIV, and cancer.

When TB becomes active in the lungs, the body begins to exhibit symptoms, such as:

• Severe cough lasting more than two weeks
• Coughing up blood or sputum (mucus from deep inside the lungs)
• Weakness or fatigue
• Loss of appetite
• Weight loss
• Night sweats
• Fever

What Are the Testing Guidelines for Travelers?

Screening for TB infection is done with a skin test. In North America, the tuberculin skin test (often called PPD for purified protein derivative) is generally used. A small amount of testing fluid is injected into the skin in the lower part of the arm, and the reaction is measured 2-3 days later.

A positive reaction, characterized by a raised bump, indicates TB infection, but it does not diagnose active disease. A negative reaction indicates the absence of infection; however, if exposure was recent, it is recommended that another skin test be done 8–10 weeks after the time of exposure.

If you are staying for an extended period in a location where TB common, it is recommended that testing be done before leaving and after returning from your trip.

What Is the Treatment?

What Kind of Protection Should You Choose?

There are no simple answers, but risk is lowest in the open air and in situations where your distance from a potentially infected person is greater.

Enclosed environments such as hospitals and prisons should be avoided. If you will be spending time in this type of setting, it may be appropriate to wear a special mask that prevents TB.

Remember that tuberculosis is not exclusively a respiratory disease. It can also be transmitted by unpasteurized milk and milk products. When traveling in regions where TB is common, avoid drinking of unpasteurized or uncooked milk and milk products.

In general, tuberculosis is not easily transmitted. But, international travelers should take preventive measures if they are at heightened risk of exposure.