If you read the newspapers, listen to the radio, or watch television, you already know about the man from Georgia who may have endangered fellow passengers when he took two long international flights while infected with a highly resistant strain of tuberculosis (TB).
To protect others from risk, the Centers for Disease Control and Prevention (CDC) has quarantined him, the first time since 1963 the agency has used its statutory power to physically isolate a citizen.
Rather than rehash the widely described story of his journeys, let me provide a broader picture of TB and its dangers.
Some of the news stories state that the man carried a "highly dangerous form of TB." In fact, all forms of TB are highly dangerous. His type of TB is no more likely to cause an infection than any other; the strain of TB bacteria in his body, however, is highly resistant to the drugs that are routinely used to kill the more common strains.
A TB infection begins when the bacteria is inhaled. These germs are sprayed into the air when an infected person coughs or sneezes, and they can remain suspended there for many hours. When inhaled, the bacteria deposit themselves in the lungs and are most often rapidly cleared from the body. Any bacteria that persist in the lungs are walled off by the body's immune system.
If this immunologic protection fails, however, by dint of its being weakened by an HIV infection, or by some other disorder, or poor nutrition, or just plain bad luck, then the infection may rapidly progress to involve large segments of both lungs. TB can even eventually disseminate into other parts of the body. Such active cases of TB affect less than 10 percent of all the infected people who have no underlying medical problems.
Although the number of TB cases in the United States has declined steadily, from 84,304 cases reported in 1953 to only 13,767 cases in 2006, TB continues to infect millions around the world. More than 8 million new cases of TB were reported in 2000, and nearly 2 million people die of the disease each year.
Most active TB infections can be cured with a combination of isoniazid (INH) and rifampin. Multi-drug resistance is defined by a failure of the bacteria to respond to either of these drugs.
The more extensively drug-resistant TB bacteria, such as the strain found in the patient from Georgia, do not respond to either of these drugs or to a bevy of other medications that can be used to treat TB. Only 49 cases of such extreme drug-resistant TB were reported in the U.S. during the 13 years before 2006, and only about a third of these patients could be cured.
Frantic efforts are now under way to identify all crew members and the passengers who were sitting close enough to him to become infected by bacteria in the surrounding air.
But let's put the situation into perspective. For several reasons, it is unlikely that many of these dangerous bacteria were in the nearby air: First, the patient is said not to have been coughing and, second, no TB bacteria have been found so far in cultures of his sputum (the material brought up from the lungs for examination).
The failure to find TB bacteria in his sputum, however, is not proof of their absence from his body, since these bacteria take many weeks to grow in culture.
Furthermore, any drug-resistant TB bacteria in the airplane cabin's air were no more likely to cause an infection than any other TB bacteria, and only a small percentage of healthy people who might inhale the bacteria would ever develop a serious TB infection.
Although these considerations indicate only a low risk that the infection spread to others during his flights, the possibility does exist and therefore warrants the extensive efforts to identify people who were sitting nearby.
The fact that this patient traveled extensively despite his infection with a difficult-to-treat form of TB and his "gentleman's agreement" not to travel underscores the need for earlier reporting of the case to the CDC and for rapid action by this agency to ensure isolation of the patient to protect others from infection.
