Rabies

Rabies

Rabies is a viral disease that causes acute encephalitis in warm-blooded animals. It is zoonotic , most commonly by a bite from an infected animal. For a human, rabies is almost invariably fatal if post-exposure prophylaxis is not administered prior to the onset of severe symptoms...

 may be transmitted through the saliva of animals.

Transmission between humans is extremely rare, although it can happen through transplant surgery

Organ transplant

Organ transplantation is the moving of an organ from one body to another or from a donor site on the patient's own body, for the purpose of replacing the recipient's damaged or absent organ. The emerging field of regenerative medicine is allowing scientists and engineers to create organs to be...

, or, even more rarely, through bites, kisses or sexual relations.

After a typical human infection by bite, the virus enters the peripheral nervous system

Peripheral nervous system

The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...

. It then travels along the nerve

Nerve

A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...

s towards the central nervous system

Central nervous system

The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

. During this phase, the virus cannot be easily detected within the host, and vaccination may still confer cell-mediated immunity to prevent symptomatic rabies. Once the virus reaches the brain

Brain

The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

, it rapidly causes encephalitis

Encephalitis

Encephalitis is an acute inflammation of the brain. Encephalitis with meningitis is known as meningoencephalitis. Symptoms include headache, fever, confusion, drowsiness, and fatigue...

. This is called the "prodromal" phase. At this time, treatment is useless. Then symptoms appear. Rabies may also inflame the spinal cord

Spinal cord

The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...

 producing myelitis

Myelitis

Myelitis is a disease involving inflammation of the spinal cord, which disrupts central nervous system functions linking the brain and limbs. The name is derived from Greek referring to the "spinal cord", and the suffix -itis, which denotes inflammation....

.

Animals

In 1932, Dr. Joseph Lennox Pawan

Joseph Lennox Pawan

Joseph Lennox Pawan M.B.E. was the first person to show that rabies could be spread by vampire bats to other animals and humans.-Education and career:...

 of Trinidad

Trinidad

Trinidad is the larger and more populous of the two major islands and numerous landforms which make up the island nation of Trinidad and Tobago. It is the southernmost island in the Caribbean and lies just off the northeastern coast of Venezuela. With an area of it is also the fifth largest in...

 in the West Indies, first discovered that infected vampire bats could transmit rabies to humans and other animals. Any mammal may become infected with the rabies virus and develop symptoms, including humans. Most animals can be infected by the virus and can transmit the disease to humans. Infected bat

Bat

Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...

s, monkey

Monkey

A monkey is a primate, either an Old World monkey or a New World monkey. There are about 260 known living species of monkey. Many are arboreal, although there are species that live primarily on the ground, such as baboons. Monkeys are generally considered to be intelligent. Unlike apes, monkeys...

s, raccoon

Raccoon

Procyon is a genus of nocturnal mammals, comprising three species commonly known as raccoons, in the family Procyonidae. The most familiar species, the common raccoon , is often known simply as "the" raccoon, as the two other raccoon species in the genus are native only to the tropics and are...

s, fox

Fox

Fox is a common name for many species of omnivorous mammals belonging to the Canidae family. Foxes are small to medium-sized canids , characterized by possessing a long narrow snout, and a bushy tail .Members of about 37 species are referred to as foxes, of which only 12 species actually belong to...

es, skunk

Skunk

Skunks are mammals best known for their ability to secrete a liquid with a strong, foul odor. General appearance varies from species to species, from black-and-white to brown or cream colored. Skunks belong to the family Mephitidae and to the order Carnivora...

s, cattle

Cattle

Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...

, wolves, dog

Dog

The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...

s or cat

Cat

The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...

s provide the greatest risk to humans. Rabies may also spread through exposure to infected domestic farm animals

Livestock

Livestock refers to one or more domesticated animals raised in an agricultural setting to produce commodities such as food, fiber and labor. The term "livestock" as used in this article does not include poultry or farmed fish; however the inclusion of these, especially poultry, within the meaning...

, groundhog

Groundhog

The groundhog , also known as a woodchuck, whistle-pig, or in some areas as a land-beaver, is a rodent of the family Sciuridae, belonging to the group of large ground squirrels known as marmots. Other marmots, such as the yellow-bellied and hoary marmots, live in rocky and mountainous areas, but...

s, weasel

Weasel

Weasels are mammals forming the genus Mustela of the Mustelidae family. They are small, active predators, long and slender with short legs....

s, bear

Bear

Bears are mammals of the family Ursidae. Bears are classified as caniforms, or doglike carnivorans, with the pinnipeds being their closest living relatives. Although there are only eight living species of bear, they are widespread, appearing in a wide variety of habitats throughout the Northern...

s and other wild carnivores

Carnivora

The diverse order Carnivora |Latin]] carō "flesh", + vorāre "to devour") includes over 260 species of placental mammals. Its members are formally referred to as carnivorans, while the word "carnivore" can refer to any meat-eating animal...

. Small rodents such as squirrels, hamsters, guinea pigs, gerbils, chipmunks, rats, and mice and lagomorphs

Lagomorpha

The lagomorphs are the members of the taxonomic order Lagomorpha, of which there are two living families, the Leporidae , and the Ochotonidae...

 like rabbits and hares are almost never found to be infected with rabies and are not known to transmit rabies to humans.

The virus is usually present in the nerves and saliva

Saliva

Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...

 of a symptomatic rabid animal. The route of infection

Infection

An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...

 is usually, but not necessarily, by a bite. In many cases the infected animal is exceptionally aggressive, may attack without provocation, and exhibits otherwise uncharacteristic behaviour. Transmission may also occur via an aerosol through mucous membrane

Mucous membrane

The mucous membranes are linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion. They line cavities that are exposed to the external environment and internal organs...

s; transmission in this form may have happened in people exploring caves populated by rabid bats.

Transplantation

Rabies is known to have been transmitted between humans by transplant surgery

Organ transplant

Organ transplantation is the moving of an organ from one body to another or from a donor site on the patient's own body, for the purpose of replacing the recipient's damaged or absent organ. The emerging field of regenerative medicine is allowing scientists and engineers to create organs to be...

 on rare occasions. Infections by cornea

Cornea

The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...

l transplant have been reported in Thailand (two cases), India (two cases), Iran (two cases), the United States (one case), and France (also a single case). Details of two further cases of infection resulting from corneal transplants were described in 1996.

In June 2004, three organ recipients died in the United States from rabies transmitted in the transplanted kidneys and liver of an infected donor from Texarkana. There were bats near the donor's home, and the donor had told others that he had been bitten. The donor is reported to have died of a cerebral hemorrhage, the culmination of an unidentified neurological disorder, although recipients are said to have been told the cause of death had been a car crash. Marijuana and cocaine were found in the donor's urine at the time of his death, according to a report in The New England Journal of Medicine.

[The surgeons] thought he had suffered a fatal crack-cocaine overdose, which can produce symptoms similar to those of rabies. "We had an explanation for his condition," says Dr. Goran Klintmalm, a surgeon who oversees transplantation at Baylor University Medical Center, where the transplants occurred. "He'd recently smoked crack cocaine. He'd hemorrhaged around the brain. He'd died. That was all we needed to know."

Because of doctor-patient confidentiality rules, doctors involved with this case would not talk about it on the record, but a few did say that had Beed not had cocaine in his blood, the E.R. doctors might have investigated his symptoms more aggressively instead of assuming he had overdosed. (Because no autopsy was done, doctors have not been able to establish whether the rabies or the drugs actually killed him.)

In February 2005, three German

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 patients in Mainz

Mainz

Mainz under the Holy Roman Empire, and previously was a Roman fort city which commanded the west bank of the Rhine and formed part of the northernmost frontier of the Roman Empire...

 and Heidelberg

Heidelberg

-Early history:Between 600,000 and 200,000 years ago, "Heidelberg Man" died at nearby Mauer. His jaw bone was discovered in 1907; with scientific dating, his remains were determined to be the earliest evidence of human life in Europe. In the 5th century BC, a Celtic fortress of refuge and place of...

 were diagnosed with rabies after receiving various organs and cornea transplants from a female donor. Two of the infected people died. Three other patients who received organs from the woman have not yet shown rabies symptoms. The 26 year old donor had died of heart failure in December 2004 after consuming cocaine

Cocaine

Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine. It is a stimulant of the central nervous system, an appetite suppressant, and a topical anesthetic...

 and ecstasy. In October 2004, she had visited India, one of the countries worst affected by rabies worldwide. Dozens of medical staff were vaccinated against rabies in the two hospitals as a precautionary measure. Associated Press reports that "Donated organs are never tested for rabies. The strain detected in the victims' bodies is one commonly found in bats, health officials said." According to CNN, "Rabies tests are not routine donor screening tests, Virginia McBride, public health organ donation specialist with the Health Resources and Services Administration, said. The number of tests is limited because doctors have only about six hours from the time a patient is declared brain-dead until the transplantation must begin for the organs to maintain viability."