Rabies is an infection caused by rabies virus. The disease is a zoonosis (plural, zoonoses) meaning it is an infectious disease spread via animal reservoirs, which can be both wild and domestic. Rabies is secreted in saliva and is most commonly spread through bite wounds, but can also be spread when infected saliva comes into contact with mucous membranes, such as in the mouth or eyes. Rabies can infect any mammal. Infected mammals including foxes, raccoons, bats, skunks, and coyotes are most likely to transmit rabies in the United States. However, in developing countries in Africa and Southeast Asia, stray dogs are most likely to transmit rabies to humans. Rabies is a significant public health concern because it is invariably fatal if untreated and treatment must begin before symptoms appear in order to be effective. For this reason all household pets and domestic livestock should receive rabies vaccinations regularly. Humans who have suffered an animal bite also receive a rabies vaccination. Governments of many nations also seek new methods of controlling rabies infection, sometimes vaccinating wild animals when rabies cases increase.
The symptoms of rabies include headache, fever, nausea, and paralysis near the bite wound. The virus directly affects the nerves, spinal cord, and brain. As the disease progresses, paralysis spreads, coupled with uncontrolled muscle spasms. Fear of water, or hydrophobia, is a common symptom resulting from viral replication in the salivary glands. Patients experiencing hydrophobia have increased saliva production and difficulty swallowing and will panic or experience pain at the thought of drinking water. Additional symptoms include hallucinations, confusion, and hyperactivity. Death typically occurs within 14 days of the onset of symptoms.Treatment of rabies infection includes vaccination immediately after exposure and introduction of antibodies that bind to rabies viral particles and present them to the immune system. Vaccine doses and antibodies are injected at the wound site. Regular vaccination is the best measure to control infection by preventing the disease. Anyone who works near animals, including veterinarians, hunters, and ranchers, is encouraged to get vaccinated regularly. Additionally, all persons are discouraged from approaching wild animals, especially those acting in an unusual or erratic manner.
Life Cycle of Polio
The disease is ancient, appearing in Egyptian paintings dating to 1500 BCE. In the early 20th century a polio pandemic affected Europe, North America, and Australia. In 1955 the polio vaccine developed and tested by American virologist Jonas Salk was officially declared to be safe and effective. Initially, demand outstripped supply, and the vaccine had to be rationed. Today, thanks to the vaccine, polio has been eradicated in the United States, and only a few hundred cases are reported globally each year.