The rabies virus can infect both animals and plants, but is best-known for infecting animals. The virus ensures its survival by transmitting to a new host when infected animals bite others, and the condition is usually fatal. It is estimated that worldwide, 55,000 people die of rabies each year, according to the University of South Carolina. A rabies virus can cause encephalitis, or inflammation of the brain, which is usually deadly unless treated very quickly.
Transmission
The rabies virus is transmitted primarily through the saliva of infected animals. The virus attacks the brain, causing mental illness and aggression which prompts animals to bite and spread the virus. The virus may also be transmitted if infected saliva comes in contact with an open wound, or mucous membranes such as those in the mouth, eyes and nose. A third method of transmission is through airborne aerosols. This is common in bat caves where infected bats expel the virus in the air, where it is inhaled by others in the cave.
Disease
Rabies symptoms depend on the viral load or amount of virus injected into the host as well as how close the bite area is to the brain. Upon infection, the virus infects both nerve and muscle cells. When muscle cells are infected, there are usually no symptoms and the virus continues to replicate in a process called incubation. The virus then moves along nerve cells until it reaches the brain and infects all types of brain cells. The result is inflammation that leads to coma and finally death. There are three stages of a rabies infection: the prodromal stage occurs within one to three days and involves unusual displays of behavior; the excitative stage lasts three to four days and causes the animal to behave in a hyperactive manner, biting anything near it; finally, the paralytic stage involves brain damage that leads to drooling and paralysis. Natural immunity does not help due to the fact that the virus spreads too quickly to the brain before the body is able to attack and neutralize the virus. Therefore, it is vital to receive a vaccination for rabies even after exposure to assist the immune system in fighting the virus.
Epidemiology
Rabies can be transmitted by a variety of animals, according to the Centers for Disease Control and Prevention. Mammals are most commonly infected, and may include domestic farm animals like cattle. In North America, skunks, raccoons, bats, foxes and dogs are the most commonly infected animals. In South America, dogs and vampire bats are susceptible, while in Europe, badgers and foxes can spread the disease.
