Rabies is a severe viral infection affecting humans and other mammals, caused by the rabies virus. It leads to encephalitis, an inflammation of the brain. Once the virus enters the central nervous system, it triggers a progressive and almost always fatal form of encephalitis.
The Viral Journey to the Brain
Rabies typically begins when the virus enters the body, most commonly through a bite or scratch from an infected animal. The virus may initially replicate in muscle or connective tissue near the bite site before entering the peripheral nervous system.
The virus then travels along the nerve fibers, moving slowly towards the central nervous system, including the spinal cord and eventually the brain. Once the virus reaches the brain, it replicates rapidly, causing neurological damage. The time it takes for the virus to travel from the bite wound to the brain is known as the incubation period, which can vary widely from as short as four days to over a year, though it is commonly one to three months. The length of this period depends on factors such as the severity and location of the wound, with bites closer to the brain generally resulting in shorter incubation times.
Manifestations of Rabies Encephalitis
Once the virus reaches the brain, clinical presentation can take two primary forms: furious and paralytic rabies. Furious rabies is the more common type, characterized by periods of hyperactivity, agitation, aggression, and confusion. Individuals may experience hallucinations, restlessness, and abnormal behaviors.
A distinctive symptom of furious rabies is hydrophobia, an extreme aversion to water, and aerophobia, a fear of drafts or fresh air. These reactions result from intensely painful spasms of the throat and larynx muscles. Spasms are triggered by attempts to drink water or even by a breath of air, causing severe discomfort and an inability to swallow. Excessive salivation can also occur due to these swallowing difficulties.
Paralytic rabies, also known as ‘dumb’ rabies, follows a less dramatic course. This form is marked by progressive muscle weakness and paralysis, often beginning at the bite site and spreading throughout the body. Symptoms include fever, headache, and neck stiffness, followed by tingling sensations and paralysis. Over time, a coma develops, leading to death.
Medical Response After Exposure
Immediate medical attention after potential rabies exposure is crucial to prevent disease. Post-Exposure Prophylaxis (PEP) is the emergency medical response designed to stop the virus before it reaches the central nervous system. PEP involves thorough wound cleansing, administration of human rabies immune globulin (HRIG), and a series of rabies vaccine injections.
Wound care begins immediately by washing the bite or scratch with soap and water for at least 15 minutes to reduce the viral load. For those not previously vaccinated, HRIG provides immediate, passive immunity by delivering antibodies that neutralize the virus around the wound. The immune globulin is typically infiltrated directly into and around the wound. The rabies vaccine stimulates the immune system to produce antibodies for long-term protection. When administered promptly and correctly, PEP is nearly 100% effective in preventing rabies.
If symptoms of rabies encephalitis develop, the prognosis changes dramatically. Once clinical signs appear, the disease is almost universally fatal, with death usually occurring within days to weeks due to respiratory or cardiac arrest. While experimental treatments like the Milwaukee protocol have been attempted, their success has been exceedingly rare, with only a few documented survivors worldwide. This approach is not a standard or reliable cure, and current evidence fails to support its widespread use.
Preventing Rabies Transmission
Preventing rabies involves public health initiatives and personal safety measures. Vaccinating domestic animals, particularly dogs, is a highly effective strategy for controlling the disease. Dogs are responsible for the vast majority of human rabies cases globally, making widespread canine vaccination programs a cornerstone of prevention efforts, helping interrupt the transmission cycle.
Individuals can also reduce their risk of exposure. Avoiding contact with wild animals like bats, raccoons, skunks, and foxes is important, as these species often carry the virus. People should refrain from approaching or feeding any wild animals, especially those that appear sick or act strangely. Teaching children to avoid unfamiliar animals and report any animal bites or scratches is a practical safety measure. Securing garbage and sealing entry points in homes can prevent wildlife from entering human habitats.