Plague on a Plane.

By NANCY GIBBS

Extensively drug-resistant tuberculosis (XDR-TB) is the kind of germ that makes public-health officials go very pale when they talk about it. TB is bad enough, wasting bodies, ravaging lungs. The multi-- drug-resistant kind is worse. And XDR is the very rare but very awful strain that has all but exhausted the medical arsenal, leaving mainly faith and force as weapons: keep the patient isolated and hope that some treatment works against it, which happens in less than one-third of cases. The good news is that most people infected with the germ won't develop the disease; there have been fewer than 50 cases in the U.S. since 1993. The bad news is that extended contact in an enclosed space--like a long airplane flight--is the perfect petri dish.

When news broke that a Georgia man had potentially infected dozens of fellow plane passengers, it sent a shudder through the global-health system. Now he's in isolation, with an armed guard outside his hospital door, and other passengers have been told to get tested. Just as there's no way to stop infected birds from migrating or dangerous viruses from mutating, the only way to stop a disease like this from spreading is to keep the carrier away from anyone he might infect. "We depend on a covenant of trust," said Dr. Martin Cetron of the Centers for Disease Control, and after the patient ignored the agency's warnings not to fly, he found himself under the first federal isolation order issued in 44 years.

The word quarantine comes from Latin for 40, the number of days Venice required ships to stay anchored before landing to prevent the spread of the Black Death in the 14th century. Since 2002 the government has claimed broad powers to isolate anyone who poses a public-health threat--including those who may have been exposed but aren't yet sick--to contain a flu pandemic or a bioterrorist attack. Various states are flexing their muscles; authorities in Arizona have locked up a TB patient because he refused to wear a mask when he went outside. In New York, patients who refuse to take their meds--an action that can promote drug-resistant strains of TB--can be confined. Such cases are a reminder that there are no antidotes yet for ignorance or indifference, and that the first line of defense against a deadly outbreak is the individual conscience.