What a difference a month makes. When a tabloid photo editor died of pulmonary anthrax in early October, not even the tabloids conjured a terrorist plot. And when it turned out there was a terrorist plot, experts assumed that the risk to most people was minimal. Unless powder has been spilling conspicuously from your hate mail, they said, you don't have much to worry about. In a sense that's still true. According to a Nov. 2 report from the Centers for Disease Control and Prevention, the anthrax attack has caused just 16 known infections (there was another confirmed case at the weekend) and four deaths. Yet the outbreak continues to defy expectations. The letterborne spores have spread far more widely than anyone could have predicted. And the death last week of a woman lacking ties to any known source of contamination has left investigators to wonder who might be stricken next. "Some of us thought we were bioterrorism experts," Surgeon General David Satcher lamented last week. "We have learned how little we knew."
Lesson one is that anthrax spores--if milled to the right size and purged of electrostatic charge--are very hard to sequester. When tainted letters started turning up in New York and Washington last month, health officials agreed they posed little danger as long as they were sealed. Now that nine mail handlers have developed anthrax and two have died, we know better. It turns out that high-speed sorting machines can shake the highly refined spores from sealed envelopes, creating invisible clouds of infectious material. At Washington's Brentwood mail facility, two people working around sorting machines inhaled lethal doses. No one knows exactly what it would take to eliminate this problem, but the CDC has issued preliminary recommendations for reducing the risk to mail handlers. In addition to gloves and face masks, the new guidelines (posted www. bt.cdc.gov) suggest placing exhaust hoods over mail-sorting machines and outfitting postal facilities' ventilation systems and vacuum cleaners with HEPA (high-efficiency particulate air) filters.
Are mail workers the only ones in need of such protection? Could a leaky letter bomb contaminate a phone bill or a wedding invitation while passing through a mail sorter? And could the ordinary mail then sicken its recipient? Ken Alibek, a microbiologist who worked in the Soviet bioweapons program before defecting to the United States, warns that even a dozen bacterial spores could cause cutaneous (topical) anthrax if rubbed from an envelope into a small break in the skin. The risk still seems small, says Dr. Robert Holzman of the NYU School of Medicine, because cutaneous anthrax isn't sweeping the areas served by affected postal facilities.
Cross-contamination is even less likely to cause the pulmonary form of anthrax, in which inhaled spores germinate in the lungs and invade the rest of the body. Animal studies suggest that it takes 2,500 to 10,000 spores to seed a pulmonary infection. It's hard to imagine stray spores on the outside of an envelope generating plumes of that magnitude. But it's conceivable that smaller doses sometimes suffice, and federal officials have gained a new respect for unlikely scenarios. The Postal Service is now acquiring electron-beam purification systems for eight major processing centers, and contemplating more ambitious measures.
Unfortunately, the threat is not confined to the mail system. There is no evidence that terrorists are spreading anthrax spores by other means, but a pair of unexplained infections raises that sobering possibility. The first involves a 51-year-old New Jersey woman who sought treatment on Oct. 18 for a large pimple on her forehead. A doctor drained yellow liquid from the sore and prescribed oral antibiotics, but the lesion "progressed and ulcerated," according to the CDC's Nov. 2 report. When her eyelid and half of her face swelled up four days later, physicians performed a biopsy, diagnosed anthrax and administered intravenous antibiotics to control it.
The New Jersey case may be the rare one Alibek envisions, in which an innocent letter picks up a few spores on a sorting machine. But Kathy Nguyen, the New York hospital worker who died of inhalation anthrax last week, is harder to account for. If an envelope caused her illness, then cross-contamination may pose a worse threat than we realized. And if it wasn't an envelope, we have to ask whether anthrax is spreading by some other means. The good news is that Nguyen remains an anomaly. If terrorists had secretly pumped aerosolized spores through a building or a subway, others would surely be dying. The bad news is that we know such attacks are possible. A paper envelope is an extremely crude device for spreading infectious aerosols. So far, says University of Minnesota bioterrorism expert Michael Osterholm, someone is firing a "powerful bullet through an ineffective gun."
Can we ever fully protect ourselves from a threat that is tasteless, odorless and often invisible? The CDC's new mail-handling guidelines--gloves, masks, dust control-- could help protect any firm or family from stray bacterial spores. By the same token, any public structure with a HEPA-equipped ventilation system should make a less inviting target for bioterror. Once an attack occurs, the challenge is to determine who's been exposed--and to administer antibiotics to anyone who was in a position to inhale the deadly spores. Inhalation anthrax has an incubation period of three to 60 days. People given antibiotics during that period can clear the infection without so much as a headache. Unfortunately, experts can still only guess at who needs treatment. Nasal swabs can help investigators map out an affected area, but an exposed person may have a negative swab. "Right now," says Dr. Julie Gerberding of the CDC, "we don't have a test to tell us who might develop anthrax in the near future."
That's why treatment is becoming such an important part of the picture. Until last month, doctors thought inhalation anthrax was essentially a death sentence once it announced its presence. The early symptoms--fever, cough, aches, malaise--resemble those of a cold or the flu. Unless they're recognized as anthrax, and treated with antibiotics, they quickly lead to shock, suffocation and death. Doctors have long assumed that patients who develop symptoms have only a 10 percent chance of surviving. But the current outbreak suggests that with aggressive treatment, the survival rate can top 60 percent (six of 10 pulmonary patients are still alive). The challenge doctors now face is to recognize the disease quickly. The symptoms may differ subtly from those of the flu; anthrax victims tend not to experience nasal congestion or runny noses. But health officials believe that analyzing symptoms is less important than assessing a person's risk of exposure. Despite the mysterious new cases, they say, public officials, media employees and mail handlers are still the most likely victims. If a person works in a known hot zone, or recalls opening unusual mail, the index of suspicion should rise even higher.
The impending flu season could complicate these efforts, flooding hospitals and pharmacies with people who need only aspirin and bed rest. "We don't want everybody coming in with the flu to get an antibiotic," says Gerberding. At what point does vigilance become paranoia? It's hard to say when so much is unknown. If we're lucky, we won't have to learn a lot more.