Rabies is not only one of the most widely known diseases, but it is also one of the first reported epizootic ailments, with records dating to approximately 2300 BC. Tablets inscribed with the laws of Eshnunna, an ancient Mesopotamian city, instruct owners to avoid bites from dogs exhibiting signs of rabies, and they pose serious fines for dog owners whose pets kill other citizens by an infectious bite.
The Greek philosopher Aristotle made note of the disease about 2000 years later, “Dogs suffer from the madness. This causes them to become very irritable and all animals they bite become diseased.” In fact the Greek word for rabies “lyssa” is retained in the genus name Lyssavirus, and the other half “virus” is actually the Latin word for poison.
Physicians have documented occurrences of rabies throughout the ages, including the first significant outbreak in 1271 AD, where thirty people in what is today Germany died after being bitten by rabid wolves. Several serious incidents were reported in 18th Century Europe and America leading to the deaths of thousands of dogs and foxes either due to the disease itself or as a preventative measure by humans. Two major breakthroughs in understanding rabies came in the 19th Century, when a German scientist, Zinke, demonstrated the transmission of rabies via the saliva of infected dogs in 1804, and when Louis Pasteur successfully vaccinated an infected man in 1885.
Today scientists have a much better understanding of the mechanics that make rabies such a nightmarish disease.
- After entering the body, the bullet-shaped virus, approximately 780 nm in length, is incubated for 20 to 90 days, during which no symptoms are observed.
- Next is the week-long prodromal phase wherein the virus travels through the afferent nerves of the peripheral nervous system, causing flu-like symptoms and pain at the site of the bite.
- Then the virus reaches the spinal cord and eventually the brain, where it replicates before passing through efferent nerve cells to the salivary glands, increasing their productivity to promote transmission.
- The acute neurological phase, also lasting about one week, can take two forms: paralytic, marked by lethargy and weakness, or encephalitic, with stereotypical symptoms such as hyperactivity, hallucinations, disorientation, and aggression.
- The acute phase is followed by coma and finally, death.
Rabies occurs exclusively in mammals, and there about 50,000 cases reported in humans worldwide, but only 1-2 in the United States on average, and nearly all of these cases are attributed to bites from stray dogs. Though saliva is the primary medium for transmission, the disease can be spread through organ transplants and even through the air, although there is only one documented occurrence of this outside of the laboratory, and it happened in a cave housing millions of infected bats. Bats are generally believed to have high rates of rabies infection, but only about 1% of bats have been found to have the disease in the US.
The World Health Organization cites rabies as one of the most neglected global health problems, because the disease is largely preventable, but due to the cost of approximately $40 per shot, people in developing nations are left vulnerable to the disease; however, organizations like Rabies in the Americas and Rabies Free World have been working to overcome this age-old disease.