Feature Article UNMET HEALTH NEEDS Painful Polio Our fight against polio—a vaccine- preventable infectious disease—is at its peak. Ensuring complete immunization of every child is the key to oust the deadly polio virus from our planet.. P. CHEENA CHAWLA HILDREN are beautiful gifts of Nature. Sheer neglect of hygiene in the early days of life can play havoc in the Cinfant body, letting germs of a wide Although polio was well the capsid. Besides protecting the variety make home in the tiny organs recognized as a human affliction for genetic material of poliovirus, the playing a dangerous game of life and long, it was only in 1908 that the culprit capsid proteins enable this virus to death. The aftermath of an infectious bug for this disease, the polio virus, infect certain types of cells. childhood illness is most appalling if was identified by Karl Landsteiner. Three different serotypes of polio survival is at the cost of living with a Polio spread widely in Europe and the virus are known to cause the disease — crippled body for whole life. This United States in late 1880s and as the poliovirus type 1 (PV1), type 2 (PV2), exactly happens when the deadly virus, virus circulated rampantly around the and type 3 (PV3) — each having a known to cause polio, strikes! globe, polio cases dramatically slightly different capsid protein. One of the most dreaded childhood increased. It was in the face of such Although all these viral serotypes are diseases, polio mostly strikes children epidemics in early 1900s, paralyzing extremely dangerous and result in the under five years of age. What saddens primarily the young, that serious work same disease symptoms, PV1 is most most is that despite the availability of on developing a potent polio vaccine closely associated with paralysis. time-tested vaccines and global efforts began. Jonas Salk first developed a in full swing to eradicate this disease, polio vaccine in 1952, and a decade From Infection to Paralysis polio still incapacitates innocent, young later, Albert Sabin designed yet Polio is an acute viral disease. The lives in a few parts of the world that another vaccine to combat polio. No word ‘poliomyelitis’ is derived from includes India. doubt, these potent protective tools the Greek poliós that means ‘grey’ and have helped in reducing the global myelós referring to the ‘spinal cord’, Dreadful Past burden of polio as the number of polio while the suffix -itis, denotes The crippling effects of polio have been cases, per year, have significantly inflammation. This disease is highly known since ancient times. Egyptian lessened over the years. infectious as it spreads through the paintings and carvings clearly depict fecal-oral route, and thus, gets people with droopy limbs and children The Polio Virus transmitted through contaminated walking with canes. An English The polio virus belongs to the genus food and water in mainly places with physician, Michael Underwood in 1789 enterovirus, which is a group of RNA poor sanitation facilities. The virus gave the first clinical description on viruses that make home in the human particles start getting excreted in the polio as ‘a debility of the lower gastrointestinal feces for several weeks following extremities’. Due to the work of tract. The basic initial infection, which is the most physicians, Jakob Heine in 1840 and structure of this infective stage as the virus quickly Karl Oskar Medin in 1890, polio was virus is very simple spreads from one to more hosts, also known as Heine-Medin disease. as it comprises a especially in areas endemic to the ‘Infantile paralysis’ is yet another single strand of virus. Sometimes, the virus also gets name for polio as it primarily affects RNA enclosed in a transmitted via the oral-oral route. children. Polio Virus protein shell called Thus, transmission of polio virus SCIENCE REPORTER, January 2010 19 C M C M C M Feature Article Scoliotic Spine Normal Spine Polio affected children (left); Equinous foot ( bottom left) and polio-affected spine (above) initial symptoms of polio infection development of minor influenza-like include sore throat, fever, fatigue, symptoms. Patients with abortive polio headache, vomiting, stiffness in the infection recover completely. neck, abdominal pain and pain in the In rare cases though, about 3% of limbs. In about 90% of cases, however, infections, the virus chooses to invade there are no perceptible symptoms, but the central nervous system (CNS). Why the polio virus is excreted in the faeces, the polio virus diverts its attention from which is why the spread of infection by gastrointestinal tract to causing such cases is very high. infection in the parts of CNS is, After dividing within however, not fully understood, though occurs if the virus is present in the saliva gastrointestinal cells for about a week, it appears to be only a chance event. or feces. The incubation period, which the polio virus spreads to the tonsils Most patients with CNS involvement is the time between the first exposure (specifically the follicular dendritic develop non-paralytic aseptic and appearance of first symptoms, is cells), the intestinal lymphoid tissue (M meningitis, which is the inflammation normally 6 to 20 days. cells of Peyer’s patches), and other of meninges—the layers of tissue As the polio virus enters the body lymph nodes. Soon the virus gets surrounding the brain. The symptoms through the mouth, it infects the cells absorbed into the bloodstream. This last for 2 to 10 days, followed by lining the throat and intestine. stage when the polio virus appears in complete recovery. On an average, 1 in Interestingly, the polio virus gains the bloodstream and starts its journey 200 of such cases progress to paralytic cellular entry by binding to special of spreading across the whole body is disease, as the virus attacks the nerve receptors, which are proteins sitting on called viremia. The polio virus is able cells that control muscle movement, due the surface of host cells. The virus then to survive and multiply within blood to which the muscles become weak, hijacks the machinery of the host cell and lymphatics for periods as long as floppy and poorly controlled, and and begins to replicate furiously. The 17 weeks, which leads to the finally completely paralyzed—a In addition to routine immunization, the Pulse Polio Immunization Programme was launched in 1995-96. SCIENCE REPORTER, January 2010 C M 20 Y K 21 Feature Article In India, vaccination against polio was initiated in 1978 under Muscles commonly weakened by polio the Expanded Programme on Immunization (EPI) and the coverage achieved by 1984 was around 40% of all infants with three doses of OPV Shoulder Muscles condition known as acute flaccid Wiping out an Muscles that Muscles behind paralysis. This is the most horrific form straighten or arm of polio as the patient is reduced to a age-old disease bend hip, or that (weakness pathetic figure of constant suffering. spread or close straightening arm) from the face of legs Back Muscles Paralytic Polio the Earth that (either side of A hapless 1% of polio cases are those houses more backbone) where the virus spreads along certain Muscles that Thumb Muscle nerve fiber pathways, mainly than 6.5 billion straighten destroying the motor neurons within people is not knee the spinal cord, brain stem, or motor cortex, which leads to the development easy. Although it Contractures of paralytic poliomyelitis. Different poses a difficult causing tight types of paralysis may occur, Muscles that cords depending on the nerves involved. challenge but lift foot Although the molecular mechanisms of paralytic polio needs to certainly, it is not be understood more clearly, there insurmountable. visibly occur various lesions/cellular abnormalities within the spinal ganglia are highest while the rate of paralysis is permanent, while cells that as these nerve cells get destroyed by the occurrence of paralysis is lowest with simply lose function temporarily invasion of polio virus. The type 2 polio virus. recover within four to six weeks. Half inflammation associated with nerve cell the patients with spinal polio recover destruction often alters the colour and Spinal Polio fully, one quarter recover with mild appearance of the gray matter in the Spinal polio is the most common form disability and the remaining quarter are spinal region, causing it to appear of paralytic polio. It occurs when the left with severe disability reddish and swollen. Other destructive polio virus invades the motor neurons changes associated with paralytic polio of the anterior horn cells, or the front Bulbar Polio occur in the hypothalamus and gray matter in the spinal column, which About 2% of cases of paralytic polio are thalamus regions of the brain. are responsible for movement of the bulbar polio, where the polio virus Early symptoms of paralytic polio muscles located in the trunk, limbs and invades and destroys nerves within the include high fever, headache, the intercostal muscles. Basically, there bulbar region of the brain stem, which difficulty in swallowing, stiffness in occurs inflammation of the nerve cells, is the region of white matter that the back and neck, asymmetrical leading to damage of motor neuron connects the cerebral cortex to the brain weakness of various muscles, loss of ganglia. Innervated by the dead stem. The destruction of nerves in this reflexes and sensitivity to touch. neurons, the muscle tissue now no region weakens the muscles, which are Paralysis generally develops between longer receives signals from the brain stimulated by cranial nerves, thus 1 to 10 days after early symptoms or spinal cord, which is why the affected resulting in symptoms of encephalitis, begin, which progresses for two to muscles become weak.