What is polio?

Poliomyelitis is a highly infectious disease caused by the polio virus. It invades the nervous system, and can cause paralysis or even death in a matter of hours.

How is polio transmitted?

The polio virus (scientifically known as the wild poliovirus or WPV) enters the body through water or food that has been contaminated with faecal material from an infected person. The virus multiplies in the intestine. From blood it may pass to the nerves of the brain stem and spinal cord. The disease mainly affects children under five years.

Only humans can catch polio. The incubation period is three-five days for minor illness and one-two weeks for paralytic symptoms. So a large number of people may have had a minor dose of polio without really being aware of it. The more severe the original flu-like illness, the more chance there is of deterioration occurring later in life (fatigue & weakness).

What are the different strains of polio?

Paralytic polio can be caused by any of three closely related strains (serotypes) of poliovirus — PV1 (poliovirus1), PV2 and PV3. PV1 is the most virulent and produces the most severe paralysis. According to the Union Ministry of Health and Family Welfare, one out of every 200 children in India is infected with this virus.

People with PV2 are often first diagnosed as having meningitis and may have gone into a coma, but often the paralysis is less severe. Those who have PV2 are more likely to have had encephalitic polio and possible coma. Damage to the brain can lead to poor memory, problems in keeping awake or falling and staying asleep. PV2 is a weaker virus and has been eradicated from India; the last case was reported from Aligarh in 1999.

PV3 is more likely to be found where there are reports of sporadic cases, not in epidemics. The rate of infection in PV3 is one in 1,000. This strain had been confined to western Uttar Pradesh for the past two years but has now spread to other districts of the state and also Bihar. Those who have PV3 seem to be more prone to developing Chronic Fatigue or Parkinson’s later in life.

There are 12 other viruses that are closely related to polio and can cause paralysis. If they had been discovered before polio vaccines stopped polio they would probably have been recorded as other polio types. At present there is no vaccine for the other types as everything is geared at eliminating the three known polio strains. But people are still being paralysed by these other strains, now called acute flaccid paralysis.

Is there a cure for polio?

No, there is no cure for polio. Polio can only be prevented by immunisation. The oral polio vaccine (OPV) is a safe and effective protection. Given multiple times, it protects a child for life. As for fear of side-effects, OPV is one of the safest vaccines ever developed. It is so safe that it can be given to sick children and newborns. It is believed to have saved millions of children around the world from paralysis.

Is injectable vaccine an option?

OPV helps in mass immunisation in densely populated and unhygienic conditions. Using OPV, all the countries in the world except India, Pakistan, Afghanistan and Nigeria have eradicated polio.

But all polio-free countries over a period of time have switched over to IPV (injectable polio vaccine). Unlike OPV, IPV gives individual protection to a child against all polio viruses. Two years back the India Experts Advisory Group suggested that the Government explore the possibility of using IPV in high-risk districts of western UP to supplement OPV. But in a country like India where wild virus is still in circulation, OPV is the best means to provide mass immunity.

How many doses of OPV does a child need?

OPV needs to be administered multiple times to be effective. The number of doses it takes to immunise a child depends entirely on his/her health and nutritional status, and how many other viruses the child has been exposed to. Children living in areas that are densely populated and with poor hygiene need higher doses of OPV.

Given that every time a polio case is reported there are a flurry of accusations against the immunisation drive, what needs to be realised is that until a child is fully immunised, he/she is still at risk from polio. So it’s important to immunise each child under five during every round and ensure that all are given the vaccine at the same time.

What is the track record of the polio immunisation drive in India?

The campaign has made tremendous progress. Before the launch of the global programme in 1988, India had, on an average, two to four lakh cases every year, which has now been reduced to a few hundred.

How many new cases have been reported?

This year, 281 cases of polio have been reported, with Uttar Pradesh leading with 223, followed by Bihar 40, Andhra Pradesh 5, Uttarakhand 4, Haryana 3, Maharashtra 2, and one each from Gujarat, Rajasthan, Delhi and Orissa.

Source: Union Ministry of Health and Family Welfare