Vaccine-preventable rabies is India’s most fatal infection
Only six persons have survived rabies infection in India since 2010, with the first case of partial recovery documented in 2002.
Encephalitis and H1N1 outbreaks grab headlines, but the world’s most deadly viral infection that kills everyone it infects is rabies, against which Louis Pasteur developed a vaccine in 1885.
Rabies is the only disease that had a 100% death rate in India in 2017, compared to 12% for Japanese encephalitis and 6% for H1N1, popularly known as swine flu, according to data from the National Health Profile 2018.
There were 4,370 rabies deaths in India in 2016, which accounted for one in three of the world’s 13,340 rabies deaths, according to the Global Burden of Disease Study estimates released last year.
This 100% vaccine-preventable viral disease that spreads to people through bites or scratches of animals, mostly infected dogs, almost always causes death the world over after clinical symptoms appear, according the World Health Organisation, which has set a target of “zero human rabies deaths by 2030”.
Only six persons have survived rabies infection in India since 2010, with the first case of partial recovery documented in 2002. Globally, there are only 15 known survivors of rabies.
Preventing deaths is possible with the use of pre- and post-exposure anti-rabies vaccination and rabies immunoglobulin injected at the site of deep wounds to stimulate the immune system to produce virus-neutralising antibodies in a week to 10 days. The first of four shots must be given immediately after the bite or scratch site has been washed with soap and clean water, detergent or povidone iodine (Betadine). Every year, more than 5 million people receive a post-bite vaccination in India, which prevents thousands of deaths annually.
With both the anti-rabies vaccine and immunoglobulin produced in India, the vaccines are available free at all government hospitals but India needs to scale up indigenous production of modern cell-culture vaccines to meet procurement delays. Each dose costs ₹350-500 at private clinics, while the rabies immunoglobulin costs between ₹650 to ₹2,500, depending on dose to be injected.
The incubation period for rabies is usually between one to three months but symptoms may appear within a week or even after a year of exposure, depending on the location of bite and viral load in the infected animal. Initial symptoms include a fever, with pain and tingling, pricking or burning sensation (paraesthesia) at the wound site from where the virus spreads to the spinal cord and brain. Death occurs for cardio-respiratory arrest.
There are two forms of the disease, which depend on path the virus takes to reach the brain. People with “furious rabies” exhibit the classic signs of hyperactivity, agitation, hydrophobia (fear of water) and aerophobia (fear of fresh air), with death occurring within two to three days.
“Paralytic” or “dumb rabies” is less dramatic and causes death from muscular paralysis starting at the site of the bite or scratch. It accounts for 30% of cases but since the symptoms are generalised, it often remains undiagnosed.
In India, as in most parts of Asia and Africa, dogs accounts for 99% of cases, but bats are a emerging public health threat in the Americas, Australia and Western Europe. Rare cases of rabies deaths reported after humans or their pets are infected by bats, foxes, jackals, mongooses and other wild carnivore hosts.
Vaccinating animals is the most cost-effective strategy for preventing rabies in people, but the 25 million stray dogs in India makes this strategy a challenge. Touching, feeding or licks on intact skin do not spread infection. Infection can occur from infected saliva coming into direct contact with human mucosa or skin wounds, but human-to-human transmission or infection from eating meat or animal tissue has not been confirmed, according to the WHO.
Since infection can only be detected only after symptoms appear using diagnostic techniques that detect whole viruses, viral antigens, or nucleic acids in infected tissues (brain, skin, urine, or saliva), prevention though anti-rabies vaccination is the only way to stop rabies deaths.
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