Everyone’s afraid of rabies, but almost no one in the United States ever gets it.
Even a hundred years ago, it was very rare, about 100 people a year got it in the early twentieth century, and today, thanks to widespread vaccination of domestic animals, the average yearly number of human cases is 2 or 3; there were only 32 cases from 1990 until the end of 2000.
In 1999 there were no cases of human rabies at all, zero. Yet however rare it is, it’s 100 percent fatal if untreated, which is reason enough to be afraid of it. In the fall of 2000, five men in five different states were diagnosed with rabies, and every one of them died, the first human rabies diagnoses since December 1998. One of the men had just arrived in New York from Ghana and had been infected in his native country by a puppy.
Rabies is much more common in developing countries than in the industrial world, and canine rabies is prevalent in Africa, Asia, and Latin America. Of the 50,000 rabies deaths each year, more than 95 percent are reported in areas where canine rabies is common. But the other four were not bitten by rabid dogs. Instead, each of them had had some kind of contact with bats. None of the five lived more than two weeks after being hospitalized.
Between 1990 and December 2000, 24 of the 32 cases of rabies reported to the CDC were attributable to bat-associated variants of the virus, even though it couldn’t always be firmly established that a bat bite was the cause of the illness. One problem is that bats are quite small, and their bite often seems a minor injury unworthy of medical attention. Moreover, some people, especially children or the disabled, can be bitten by bats without reporting it or even knowing that they have been bitten.
Rabies can be carried by all species of mammals, and it’s just as fatal to them as it is to humans. It causes encephalitis, swelling of the brain. Different species carry different variants of the virus, and in addition to bats, raccoons, skunks, foxes, and coyotes are major reservoirs of the virus in the United States.
Although there are other ways of getting the virus, they are very rare in comparison to the most common way: by the bite of an infected animal. When a raccoon, for example, is bitten by a rabid animal, the virus enters with the infected saliva, spreads through the nerve to the spinal cord, and then incubates for one to three months. During this period, the animal shows no sign of illness. As the virus moves to the brain, it multiplies and passes to the salivary glands. At this point the animal is sick, and the sickness is brief: within a week, the raccoon is dead.
In humans, the first sign of rabies infection (as with so many other illnesses) is flu-like symptoms: malaise, headache, and fever lasting for several days. Soon brain function is affected, causing anxiety, confusion, agitation, hallucinations, and insomnia. By the time the clinical symptoms have appeared, it’s too late: there are exactly six documented cases of people surviving after symptoms have appeared, and all of them had had some kind of pre or post-exposure prophylaxis.
The only way to avoid dying after being infected with rabies is to get immediate prophylactic treatment before symptoms appear. There are several tests required if you want to make sure you haven’t been exposed, no single test will rule out the possibility. These tests include serum, spinal fluid, skin biopsy, and saliva examinations to test for the presence of antibodies to the virus. It’s easier to figure out if an animal is rabid, you kill it and test its brain tissue, a procedure that can be carried out within a few hours. Knowing if the animal that bit you was rabid is obviously very important. If it wasn’t, you can relax. If it was, you need prophylaxis immediately.
There is a very effective rabies vaccine that was developed about 20 years ago. It works when administered before exposure, and works equally well when administered just after exposure. About 58,000 people in the United States are treated every year with the vaccine. Most people don’t need pre-exposure vaccination, that’s reserved for high risk groups such as veterinarians, animal handlers, and people who work with certain laboratory animals. Anyone who has frequent contact with potentially rabid raccoons, bats, skunks, cats, dogs, or other mammals should also be vaccinated, and if you’re traveling to areas of the world where rabies is endemic, you should consider getting the vaccine.
If you’re exposed to an animal that is possibly rabid, then you need the vaccine as soon as possible, as well as one dose of immune globulin. Post-exposure, the rabies vaccine is given in five shots over a 28-day period, and the immune globulin is administered along with the first shot.
The vaccine, contrary to what you may have heard, is relatively painless and given in the arm, just like a flu shot. It has never, not even once, failed to work when given promptly. “Promptly” does not mean that you have to panic, the CDC calls it a “medical urgency,” not a “medical emergency.” The incubation period of the virus, that is, the time between the initial contact and the appearance of symptoms, is very variable and can be anywhere between a few days and several months. But there is time to consult with your physician and with public health officials regarding the need for the vaccine.
If you are bitten, the health care worker will want some facts, including where the incident happened, what kind of animal bit you, whether the exposure was provoked or unprovoked, whether the animal has been vaccinated, and whether the animal can be or already has been captured so that it can be tested. The most important thing is to seek care promptly. As we noted, rabies is, for all practical purposes, 100 percent fatal if you don’t treat it, and 100 percent preventable if you do.
You can’t get rabies from another human by casual contact such as touching or contact with urine, blood, or feces of an infected person. Theoretically, you could get it from being bitten by a human with rabies, but there has never been such a case reported. Nor does contact with a person receiving post-exposure prophylaxis mean you’ve been exposed to rabies. The only human-to-human transmission ever documented happened among eight people receiving corneal transplants in five different countries (two in Thailand, two in India, two in Iran, one in the United States, and one in France). New guidelines for the acceptance of corneas for transplant have reduced this tiny risk even further.
Why bats? There seems no reason to believe that bats are any more susceptible to rabies infection than many other mammals, but it may be that close human contact with them is more common than with any of the other usual wild reservoirs of the virus: raccoons, foxes, skunks, and coyotes.
Unlike these other mammals, bats often get into houses, where they nest and breed. Other small wild mammals that live close to people or in their houses, rodents like mice, squirrels, and chipmunks, for example, have never been known to cause rabies among humans, even though they can theoretically be infected with the virus. The rodent that is most commonly infected is the woodchuck (sometimes called a groundhog), but most people only see them from a speeding car, sometimes alive, and probably just as often squashed beyond recognition in the middle of the road. So that leaves bats, which most people find a rather unappealing creature to begin with, for at least one good reason and several bad ones.
Although there is a species of bat, Desmodus rotundus, that feeds on the blood of vertebrates, including humans, these bats are tropical creatures that do not live in North America. North American bats do not suck your blood, they’re not blind, they’re not birds, and they’re not rodents.
There are several different species that are common in North America, including the red bat, the hoary bat, the Mexican free-tailed bat, the big brown bat, the little brown bat, and the silver-haired bat. This last species is the one most commonly associated with human rabies. Bats are mammals, and their diet consists mainly of insects. Eating insects, especially agricultural pests, makes them an essential part of the ecosystem everywhere in the world from rain forests to deserts. Living safely with them is important to everyone.
Although the only sure way of knowing if a bat is rabid is by a laboratory test, any bat found where bats are not normally seen, in the middle of the lawn during the day, for example, or a bat that appears unable to fly should be considered suspect. If you wake up and find a bat in your room, you should seek medical attention even if you can’t find a bite on your body.
You can’t get rabies by seeing a bat in the attic or in a cave or at a distance, and you can’t even get it from contact with bat guano or urine. Touching a bat is a bad idea, but you can’t get rabies by touching its fur. Only getting the saliva into your body thorough a wound, your eyes, your nose, or your mouth will do it.
Well, enough of the great outdoors. Let’s go home, take a shower, get dressed, and go out to a restaurant for a delicious dinner. Let’s relax a little. But not too much.
