Mystery Killer

A possibly more virulent strain of rabies is carried by a reclusive species of bat whose bite is barely detectable.


Why is rabies like a wedding?" Charles Rupprecht, known as the "rabies guru" of the Centers for Disease Control and Prevention, tells how he put the riddle to public health workers in Virginia recently, giving eight talks in two days.

Usually such talks focus on pet vaccination, dealing with strays, or raccoon rabies, which in Maryland has leapt from seven cases in 1981 to 346 last year. But this time there was an added incentive to come: A few months earlier, Virginia had something rare enough happen that most doctors never encounter it. A person died from rabies.

Last year might have passed without a single rabies death in the United States if not for the man who got sick about a week before Christmas. The Nottoway Correctional Center inmate complained of back pain, then of vomiting and cramps, then of muscle spasms and tremors. He was sent to Richmond for tests that ranged from a CAT scan to one for pesticide intoxication. Though he had no sign or history of an animal bite, his doctor considered rabies next. Tests were positive. The patient died Dec. 31. He was 29. The virus was traced to a bat bite.

Widespread pet vaccination of dogs, cats and even ferrets has created a public-health success story: Human rabies deaths in the United States are down to about three a year. That success comes at a yearly national cost of at least $300 million -- one CDC estimate is as high as $1 billion -- for rabies prevention and treatment.

Yet within these rare deaths is an emerging mystery. In 19 of the 27 deaths since 1990, neither doctors nor victims and their families could pin down how the victim caught the virus. All they knew for sure is what the tests showed: It was most often a rabies strain found in silver-haired bats, a reclusive and solitary species that usually avoids humans like, well, the plague. None came from the little brown bat, the species that people in the Baltimore-Washington area are most likely to see.

The last rabies death in Maryland, in 1976, came from a bat bite. The woman knew she was bitten, and the bat was caught and tested. Its species wasn't recorded. For her, the treatment failed. A more effective treatment used since the late '70s hasn't failed yet, according to the CDC.

The 19 deaths since 1990 didn't happen because of treatment failure but because there was no reason to suspect rabies. The victims didn't remember being bitten by any animal. Some didn't remember ever even seeing a bat. Yet there had to have been direct physical contact with one.

This puzzle is how rabies is like a wedding, Rupprecht says: "It's something old, and something new." Rabies is one of the oldest viruses known, but the new deaths today might be evidence of an evolving and possibly more virulent virus.

"It's quite a peculiar situation," says Rupprecht, chief of the rabies section at the National Center for Infectious Diseases. In North America, he says, "we're surrounded by rabies from raccoons, skunks, foxes." Yet, he says, the deaths most often have been caused not by these land animals but by the strain found in this obscure bat species.

A look at a CDC map tracking where rabid raccoons are found shows a strain that covers much of the eastern United States. Even 10 years ago, many of these states hadn't reported a single rabid raccoon.

Raccoons brought by hunters from the Deep South to West Virginia and Virginia brought wildlife rabies to Maryland, says Clifford I. Johnson, Maryland's public health veterinarian. "They just multiplied, and it spilled over."

Rabies apparently spreads among land animals far more readily than among bat colonies; the percentage of infected bats is usually pretty steady -- just half of 1 percent, bat experts say. And bats usually only infect other bats and sometimes horses, while land animals can pass infections easily among each other, to domestic pets and humans.

Once the symptoms show up, rabies is fatal. In recorded history, says Bela Matyas, medical director of the epidemiology program at the Massachusetts Department of Public Health, only four people have survived it, and three of these had had previous vaccinations.

"Rabies is an untreatable disease," says Matyas. "We don't treat rabies, we treat exposure to rabies. What we're actually trying to do is to destroy the virus before it can cause disease."

In the incubation period -- usually a few weeks, but sometimes several months -- as the virus works its way from the contact site into the nervous system, injections can almost always wipe it out. This used to mean a painful 26 shots in the stomach. The current and more effective treatment is usually five intramuscular shots over about a month, and one or more injections around the site of the bite or contact. It might make you feel a little ill, but there are no severe side effects. Its main drawback is its cost, which can be up to $4,000, depending on a person's size and hospital costs.

The problem is: You can be cured only if you realize you've been bitten.

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