Final answer:
The rabies virus affects the nervous system and is spread through infected animal saliva. This neurological disease leads to severe behavioral changes, and if untreated by vaccination after exposure, it is almost always fatal. Strict animal control and vaccination are essential in controlling this disease.
Step-by-step explanation:
The type of virus that affects the nervous system and is usually spread through the saliva of infected animals is the rabies virus. Rabies is known for entering the nervous tissue shortly after transmission and migrating to the central nervous system. This results in changes in behavior such as hydrophobia (fear of water), aggression, and motor dysfunction. Rabies is a neurological disease caused by a virus that can infect any mammal, often leading to death within weeks. Human infection rates, while lower in the United States due to strict animal control measures, remain high in parts of Africa and Asia. The majority of human cases globally are due to dog bites. Vaccination post-exposure is crucial because once symptoms develop, rabies is almost always fatal.
The rabies virus belongs to the Rhabdoviridae family and has a single-stranded RNA core with an enveloped helical capsid. Upon transmission via infected saliva, the rabies virus travels through the peripheral nervous system before it reaches and impairs the brain. Louis Pasteur developed the first rabies vaccine, which is still used today to prevent the disease after suspected exposure, effectively preventing the virus from progressing to the central nervous system.