For centuries, tuberculosis (TB) has plagued countries worldwide. But in 1940, the first drug treatments were developed and gradually the incidence of tuberculosis diminished, particularly in developed countries where these medications were widely available.
The problem is, it's coming back.
According to Centers for Disease and Prevention (CDC), there are about 14,000 cases in the US. The World Health Organization (WHO) estimates that, in 2005, 1.6 million deaths worldwide were related to TB. International travelers today need to be aware of TB, in part, health officials say, because travel may increase the risk of contracting TB.
According to WHO, TB has increased in the last few years due to:
- The spread of HIV/AIDS
- Emergence of drug-resistant strains of TB
- Increased travel and immigration worldwide
International travelers are at increased risk for contracting TB for two reasons:
- They are more likely to visit countries where TB is prevalent
- Their mode of transportation is frequently a confined area (such as an airplane), where they may share air space with someone who has active TB
The Stop TB Partnership lists the countries with the highest rates of TB. The top ten countries with the most cases are:
- India
- China
- Indonesia
- Nigeria
- Bangladesh
- Pakistan
- South Africa
- Ethiopia
- Philippines
- Kenya
Although health officials stress that TB is more commonly transmitted from repeated daily exposure, the CDC documented its first case of proven TB transmission from one airplane passenger to four other passengers in 1995, and researchers continues to monitor this risk. A study published in the
Lancet
found that travelers staying long-term in countries with high rates of TB had the same or greater risk as residents of those countries.
Tuberculosis is caused by
Mycobacterium tuberculosis
, which can attack any part of the body, but usually settles in the lungs (called pulmonary TB). When someone with active pulmonary 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 rapidly 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:
When TB becomes active in the lungs, the body begins to exhibit symptoms, such as:
- Severe cough lasting more than two weeks
- Pain in the chest
- Coughing up blood or sputum (mucus from deep inside the lungs)
- Weakness or fatigue
- Weight loss
- Night sweats
- Chills or fever
TB infection is diagnosed through 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 usually larger than 10 millimeters across, 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 performed 10-12 weeks after the time of exposure.
For travelers staying one month or longer in countries where TB is prevalent, it is recommended that testing be done before and after exposure, with repeat testing at 1-2 year intervals if exposure continues. Pre-departure testing should generally be done with a
two-stage method
to check for “boosting.” In the two stage method, one TB test is given and read after 48-72 hours. If the test is negative, then a second test is given in a separate site within a week. This test is also read in 48-72 hours.
TB is curable when treated consistently. However the medication must be taken for the entire prescribed duration. Failure to adhere to the prescribed dosage may result in development of new drug-resistant TB strains that may not be curable.
For people in high-risk categories (eg, HIV positive, weakened immune system) or asymptomatic people with positive skin test results, the drug isoniazid (INH) may be prescribed for at least six months as preventive therapy.
A vaccine for TB, called BCG, is available in many countries but is not routinely used in the US. The vaccine does not prevent transmission of the TB bacteria, but it may help prevent it from becoming active once a person is infected.
If you have active TB, your treatment will most likely include two or more of the following medications for at least one year:
- Isoniazid (INH)
- Rifampin
- Pyrazinamide
- Ethambutol
- Streptomycin
For active pulmonary TB, you will need to isolate yourself from coworkers, friends, and family so as not to infect them. If after several weeks of taking medication your symptoms resolve and there is no bacteria in your sputum, you will no longer be infectious and may resume normal activity while continuing to take the medication.
If you are traveling, 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 exceeds three feet. TB infection is quite unlikely if you are exposed for less than several hours—so casual contact with air containing TB bacteria is relatively safe (for example, being briefly in the immediate vicinity of a person who is coughing).
Long bus and train trips may pose some risk if one or more of your fellow passengers has active tuberculosis. It is probably wise to keep your distance from people who are actively coughing. In some countries, it is common to wear a surgical mask if you have a cold or the flu. You may want to wear one, too, to protect yourself from people who are coughing.
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.
