About 50,000 to 100,000 people die from rabies every year, primarily in Asia and Africa, Dr. Vicente Corrales-Medina, infectious diseases fellow at Baylor College of Medicine, writes in "Current Medical Diagnosis & Treatment." In the United States, two to three people die annually, the Centers for Disease Control and Prevention (CDC) says. In 2008, there were 6,841 reported cases of animals infected with the rabies virus.
Viral Characteristics
The rabies virus has the shape of a bullet, with "spikes" that stick out all over it. Many of the viruses in the same family as the rabies virus can infect insects and plants, Janet Butel, chairwoman of the Department of Molecular Virology and Microbiology at Baylor College of Medicine, writes in "Jawetz, Melnick & Adelberg's Medical Microbiology." The rabies virus can infect only warm-blooded animals, which includes people. Only certain bats can recover from a rabies infection.
Development of Disease
The "spikes" are made out of glycoprotein, or sugar and protein. The virus uses the spikes to attach itself to cells. At the place where it enters the body, it reproduces itself there in the muscle. Then, it uses the nerves to get to the central nervous system, or the brain and spinal cord. It reproduces and infects the brain, causing what is called encephalitis, or inflammation of the brain. The virus can spread to other places of the body except for the blood, according to Butel.
Transmission
In 2008, 93 percent of rabies cases involved wild animals. Raccoons were the most commonly infected animal, then bats, skunks and foxes, according to the Centers for Disease Control and Prevention. The rabies virus lives in the salivary glands of infected animals. People usually become infected if the virus is in an animal's saliva at the time it bites a human. The virus can also be transmitted through the mouth, nose, eyes, a cut in the skin, organ transplants, blood vessel transplants and even corneal eye transplants, although these types of transmissions are rare.
Symptoms
The animal bite will be painful. Symptoms may also include nausea and vomiting, headache, fever and a sore throat. About 10 days after a bite, most people will have symptoms that include hallucinations, nervousness, increased perspiration, drooling and perhaps a fear of water. When they try to swallow, they can develop spasms in the muscles of their throat. Instead of these symptoms, a minority of people can develop paralysis. All rabies infections eventually lead to seizures, coma and death.
Treatment
More than 99 percent of people die who become infected and then develop symptoms, Butel writes. She explains that if the symptoms have already started, no treatment will help. Because symptoms start about 10 days after a bite, people who think they may have contracted the rabies virus must get help immediately. A physician will thoroughly clean the wound with soap and water, give the rabies immune globulin and vaccination. Immune globulins are antibodies that have been collected from the plasma of blood donors. The immune globulin is one injection. The vaccine is five injections, given on day 0, day 3, day 7, day 14 and day 28. Those who may be at risk for getting rabies should be immunized with three injections, administered on day 0, day 7 and day 21 or 28.
References
- Centers for Disease Control and Prevention: Rabies Surveillance Data in the United States
- "Current Medical Diagnosis & Treatment 2009"; Stephen McPhee, M.D., Maxine Papadakis, M.D.; 2009
- "Jawetz, Melnick, & Adelberg's Medical Microbiology"; George Brooks, M.D., Karen Carroll, M.D., Janet Butel, Ph.D., Stephen Morse, Ph.D.; 2007
