Rabies is a viral disease that causes inflammation of the brain in humans and other mammals. It is spread through contact with saliva from an infected animal, usually through bites. Rabies has one of the highest case fatality rates of any infection, close to 100% once symptoms appear. However, rabies can be prevented through prompt treatment after exposure and through vaccination of domestic animals and humans. With concerted global efforts, rabies could potentially be eliminated in humans.
What is rabies and how is it transmitted?
Rabies is caused by lyssaviruses, including the rabies virus and Australian bat lyssavirus. These are RNA viruses that infect the central nervous system of mammals. The rabies virus is present in the saliva of infected animals and is most often transmitted through bites. Less common means of transmission include getting infectious material like saliva in open wounds or mucous membranes.
In up to 99% of cases, rabies is transmitted through the bite or scratch of an infected animal. Dogs are the most common source globally, but many different mammals can be infected, including bats, raccoons, skunks, foxes, cats, cattle and monkeys. Wild animals like bats and raccoons are the most frequent source in the United States today.
After entering the body, typically through broken skin, the virus travels along nerves to the brain and causes an inflammatory reaction called encephalitis. As it progresses, rabies causes brain dysfunction, anxiety, confusion, agitation, hallucinations and insomnia. Because of the virus’ effect on the brain, infected animals often exhibit unusual behavior. Dogs may become uncharacteristically aggressive, while bats may lose the ability to fly and be found grounded during the daytime.
What are the symptoms of rabies in humans?
The early symptoms of rabies are nonspecific and may resemble the flu. Within 1-3 months after exposure (but sometimes sooner or much later), the following symptoms normally develop:
– Fever
– Headache
– Nausea
– Vomiting
– Agitation
– Anxiety
– Confusion
– Hyperactivity
– Difficulty swallowing
– Excessive salivation/drooling
As the disease advances, more specific neurologic symptoms appear:
– Insomnia
– Confusion
– Partial paralysis
– Excitation
– Hallucinations
– Agitation
– Delirium
– Abnormal behavior
– Hydrophobia (fear of water)
– Death
Without treatment, progressive brain inflammation causes coma and eventual death within 3-10 days after the onset of symptoms. In up to 20% of cases, paralytic rabies develops instead, causing muscle weakness, paralysis and loss of sensation.
How deadly is rabies?
Once clinical signs of rabies appear, it is virtually 100% fatal. Less than 10 documented cases of human survival from clinical rabies have been recorded, and only two have recovered without receiving the rabies vaccine after exposure. With aggressive treatment, there is still only a less than 10% chance of survival once rabies reaches the brain and causes symptoms.
According to the WHO, rabies results in approximately 59,000 human deaths worldwide per year, with over 95% occurring in Africa and Asia. India has the highest rate of human rabies globally, accounting for approximately 36% of deaths. Children under the age of 15 account for 40% of those killed by rabies. Mortality is highest in rural communities where access to post-exposure prophylaxis is limited.
How is rabies diagnosed?
Because early symptoms are nonspecific, rabies can be difficult to diagnose in the initial phase. However, there are tests that can determine if someone is infected with rabies before severe symptoms begin.
During the early stages, diagnosis may involve:
– Virus-specific antibody testing in the blood – Antibodies normally develop 1-2 weeks after initial infection.
– Testing saliva, spinal fluid or skin biopsies for viral RNA, viral antigens, or antibodies – These tests can confirm the presence of the rabies virus.
– MRI or CT scan – May show signs of brain inflammation.
Once neurological symptoms are present, rabies can often be diagnosed clinically based on characteristic signs of brain dysfunction. Diagnostic tests are still important and may include:
– Detection of viral nucleic acid in saliva, spinal fluid or skin samples
– Isolation of rabies virus from saliva, spinal fluid or brain tissue
– Testing spinal fluid for antibodies against rabies virus
– Skin biopsy of hair follicles at the nape of the neck
How is rabies treated?
There is no effective treatment for rabies once central nervous system symptoms develop. At this point, care is focused on comfort and quality of life before inevitable death. Sedatives and pain medication may be used to relieve suffering.
However, rabies can be prevented through prompt post-exposure prophylaxis if administered before symptoms start. After suspected exposure, wound care and a course of rabies vaccine is highly effective at preventing disease.
Post-exposure treatment may include:
Wound care
Thoroughly washing the wound site with soap and water to decrease the amount of virus present. Applying antibiotics if needed.
Passive immunization
A one-time injection of human rabies immunoglobulin (HRIG) provides immediate antibodies that help neutralize any virus present in the wound. HRIG is injected at the site of the bite if possible.
Vaccination
A course of 4-5 vaccine doses over 2-4 weeks. The rabies vaccine provokes an immune response that can clear the virus before it reaches the brain. Modern cell-based vaccines are very safe and effective.
This post-exposure prophylaxis is nearly 100% effective if administered promptly after exposure. However, delaying treatment diminishes its benefit. Once rabies symptoms occur, it is too late for these measures to work.
How can rabies be prevented?
Rabies prevention centers on reducing exposure and providing prompt post-exposure prophylaxis to anyone at risk. Some key prevention strategies include:
Domestic animal vaccination
Many regions require routine rabies vaccination of dogs, cats, ferrets, and sometimes other domestic animals. This creates an immune barrier between rabies reservoirs in wildlife and humans.
Animal control programs
Stray dog management, habitat modification and wildlife population control can help reduce the spread of rabies in animal reservoirs. Oral rabies vaccine baiting has also been used in some areas to immunize wild carnivores by leaving vaccine-laden food for them to eat.
Bite avoidance and education
Children should be taught not to approach or touch unknown animals. Bites should be thoroughly washed. Any possible exposure, even if unclear, warrants seeking medical evaluation for rabies post-exposure prophylaxis.
Pre-exposure immunization
Those at high risk of rabies exposure through work or travel may receive a 3-dose pre-exposure rabies vaccine course. This does not eliminate the need for prompt treatment after a bite, but does simplify post-exposure prophylaxis to only require two vaccine doses and no HRIG.
Public health surveillance and access to post-exposure treatment
Increased availability of rabies testing facilities, human and animal vaccine, and educational campaigns are also key to preventing human rabies deaths.
What is the goal for rabies prevention globally?
In 2015, the WHO, World Organization for Animal Health (OIE), Food and Agriculture Organization of the United Nations (FAO), and Global Alliance for Rabies Control (GARC) released a plan to end human deaths from canine-transmitted rabies by 2030. This United Against Rabies collaboration coordinates mass dog vaccination and educational programs in rabies-endemic regions of Africa and Asia to create a sustainable infrastructure for rabies prevention. As of 2020, GARC estimates that human rabies deaths have decreased by approximately 40% in these focus countries compared to 2015 estimates.
While rabies will likely persist in wild carnivore populations, animal vaccination programs and prompt human post-exposure prophylaxis access could one day make human rabies deaths fully preventable globally.
Could rabies ever be eradicated?
Eliminating rabies completely is challenging because the virus can persist indefinitely in some wild animal reservoirs. Mass immunization of domestic dogs and cats has succeeded in eliminating canine rabies transmission in the United States, Western Europe, and some Asian and Latin American countries. However, rabies remains endemic in wildlife species like bats, foxes and raccoons in much of the world.
Unless wildlife vaccination or population control efforts expand dramatically, rabies will likely continue to cycle in these animal reservoirs. Complete global eradication may not be feasible given current tools. However, preventing human rabies deaths through domestic animal vaccination, education and improved healthcare access could be attainable if sufficient resources are dedicated to those in high-risk regions.
What should I do if exposed to rabies?
Any possible exposure to rabies virus should be taken very seriously. If you are bitten, scratched or otherwise come into contact with the saliva or neural tissue of a potentially rabid animal:
1. Immediately wash the wound thoroughly with soap and running water for at least 15 minutes. Apply an iodine-based disinfectant if possible.
2. Seek medical care to receive rabies post-exposure prophylaxis within 24 hours. The sooner treatment begins, the better. Delaying beyond 6-10 days may be too late.
3. Your doctor will administer rabies vaccine and HRIG injections based on your exposure risk. Stay on schedule with all follow-up vaccine doses to complete the series.
4. Even if previously vaccinated, post-exposure treatment should still be received as it is more effective than pre-exposure vaccine alone.
With timely wound care and vaccination, almost all rabies exposures can be successfully treated. However, without treatment rabies is close to 100% fatal once symptoms start. Do not take any chances with potential exposure.
Key facts about rabies
- Rabies is caused by lyssaviruses and transmitted through contact with infected saliva.
- Over 99% of cases result from an infected animal bite or scratch.
- Once symptoms occur, rabies is almost always fatal within 3-10 days.
- Rabies can be prevented through pet vaccination, bite avoidance and prompt post-exposure prophylaxis.
- More than 95% of rabies deaths occur in Africa and Asia, areas with limited healthcare access.
- Children are disproportionately affected, comprising 40% of deaths.
- Mass dog vaccination and human pre-exposure immunization have eliminated canine rabies in some regions.
- Global deaths have decreased approximately 40% since 2015 through focused intervention programs.
- While global eradication may not be feasible soon, human deaths can potentially be eliminated with sufficient vaccination and educational efforts.
Conclusion
Rabies remains an important public health threat globally, responsible for tens of thousands of preventable deaths each year. However, safe and effective vaccines exist that can prevent the disease in humans and domestic animals. Bite prevention education, pre-exposure immunization, coordinated pet vaccination and wildlife control efforts could help halt rabies transmission to humans and eventually eliminate this dreaded disease as a cause of human mortality worldwide.
