Polio free does not mean paralysis free

 http://www.thehindu.com/opinion/lead/polio-free-does-not-mean-paralysis-free/article4266043.ece

There is no room for complacency that India has eliminated this crippling disease as Uttar Pradesh and Bihar have recorded a high incidence of a condition symptomatic of it

Identifying children who suddenly display muscle weakness, often not moving one or more of their limbs as a result, forms the cornerstone of polio surveillance. Such children could have “acute flaccid paralysis” (AFP) that is symptomatic of polio , a disease caused by a virus. But AFP can also arise for other reasons, including infection by non-polio pathogens.

No child in India has been diagnosed with polio for nearly two years now and all the indications are that the virus responsible for it is no longer circulating here. However, the country’s polio surveillance system has indicated a sharp increase during recent years in the number of non-polio AFP cases.

Alarming data

Data published by the World Health Organisation show that close to 8,000 non-polio AFP cases were identified in India during 2003. They went up to over 12,000 the following year, more than 26,000 in 2005 and crossed 40,000 by 2007. In 2011, there were more than 60,000 non-polio AFP cases.

A good polio surveillance system ought to pick up all AFP cases among children so that they can be screened for poliovirus infection. On average, only about one child out of every 200 children carrying the poliovirus develops AFP. Such cases must be identified so that appropriate immunisation measures can be undertaken.

India’s polio surveillance shows that the country is polio-free. But it also indicates that the country now has the world’s highest rate of non-polio AFP cases. According to data published in WHO’s Weekly Epidemiological Record, India’s annualised non-polio AFP rate for 2011 stood at 15.06 per one lakh children below 15 years of age, compared to a global rate that year of 5.48.

Moreover, most of the country’s non-polio AFP cases occur in just two States — Bihar and Uttar Pradesh. They accounted for about 61 per cent of the 53,000-odd non-polio AFP cases identified in the country in 2012, according to data from WHO’s National Polio Surveillance Project. As a result, the two States have far higher annualised non-polio AFP rates than other States — around 34 for Bihar and about 23 for Uttar Pradesh. The rate for the country as a whole is slightly over 12.

“The increased non-polio AFP rate is due to increased reporting of AFP cases due to deliberate efforts of the programme to increase the sensitivity of the surveillance system since 2004,” according to the WHO Country Office for India. In a written response provided to this correspondent, the health body said these efforts were more intense and closely monitored in the traditionally polio-endemic states of Bihar and U.P., resulting in even higher rates of reporting of AFP cases in those States.

In 2004, a number of steps were initiated to strengthen surveillance in order to accurately and more rapidly detect all polio cases in the country, it said. Those measures included expanding the definition of AFP; increasing the number of AFP reporting sites; increasing the number of active surveillance visits; and more training for health professionals on what constituted an AFP case.

Since then, the number of AFP cases that were reported and investigated continued to increase, it noted. This was not due to an increase in the incidence of a specific disease that might cause these symptoms. Rather, it was the direct result of surveillance activities for AFP cases being strengthened.

The programme in India had taken a much broader interpretation of what would qualify as an AFP case than other countries have. Although facial paralysis would not be part of a standard definition of AFP, it was included in that definition for India. Other similar examples were diseases like meningo-encephalitis, Bells palsy, post-diphtheria polyneuritis and spinal muscular atrophy. Data had shown that broadening the case definition led to the detection of some polio cases that would have otherwise been missed, the WHO Country Office noted.

Moreover, in the remaining polio-endemic countries of Nigeria, Pakistan and Afghanistan too, efforts to strengthen polio surveillance were resulting in increased non-polio AFP cases being reported, it added.

The high non-polio AFP rates in the country ought to be a “red flag”, remarked T. Jacob John, a leading virologist who was with Christian Medical College, Vellore, and is known for his work on polio eradication.

With heightened polio surveillance, sick children with suspected paralysis or possible neurological maladies were being identified and tested by the polio surveillance system, he remarked. However, the neurological disorders given by the WHO Country Office as examples of the expanded definition of AFP were likely to account for only a small part of the increase in non-polio AFP cases being seen in India.

No clear picture

Unfortunately, the cases of children with non-polio AFP were not being monitored by either the polio eradication programme or the larger state health care system. As a result, there was no clear picture of what was causing the AFP, the kind of diseases these children displayed, or how many of them were seriously affected, he pointed out.

A range of non-polio pathogens could produce AFP, said Dr. John. With many such pathogens, the paralysis they caused would often disappear in a short period of time. However, others were capable of causing quite serious diseases, disability and even death.

Two teams of Indian scientists recently studied the sorts of enteroviruses found in children with non-polio AFP. Enteroviruses are a diverse group, most of which replicate in the alimentary tract. The poliovirus is part of this group. Several non-polio enteroviruses have been associated with a range of acute and chronic human diseases, including polio-like paralysis.

In a study published in 2009, a team at the Sanjay Gandhi Postgraduate Institute of Medical Sciences in Lucknow tested over 46,000 stool samples from children with AFP in U.P., Bihar and other northern States between 2004 and 2007. In the other study, C. Durga Rao of the Indian Institute of Science, Bangalore, and his colleagues looked for enteroviruses in stool samples collected from more than 2,700 children with non-polio AFP in Kerala, Karnataka and Uttar Pradesh between 2007 and 2009.

Enteroviruses

Both groups found that only about 30 per cent of the non-polio AFP cases were associated with enteroviruses. These viruses could therefore only partially explain the non-polio AFP cases being detected.

In a paper published early last year in the Indian Journal of Medical Ethics, Neetu Vashisht and Jacob Puliyel of the St. Stephens Hospital, Delhi, gave another perspective on the issue. Children in Bihar and U.P. have received more doses of oral polio vaccine than elsewhere in the country. The oral vaccine, it was found, became less efficacious in the face of gut infections and diarrhoea that were widely prevalent in those States.

In their paper, Dr. Vashisht and Dr. Puliyel analysed the non-polio AFP rates across all States over 10 years up to 2010, and found that the rate “increased in proportion to the number of polio vaccine doses received in each area.” In 2012, the number of doses of oral vaccine given to children in Bihar and U.P. had come down and, for the first time, there was a decrease in the non-polio AFP cases in those States, Dr. Puliyel told this correspondent.

There was need for “a critical appraisal to find the factors contributing to the increase in non-polio AFP with increase in OPV [oral polio vaccine] doses — perhaps looking at the influence of strain shifts of entero-pathogens induced by the vaccine,” said Dr. Vashisht and Dr. Puliyel in the paper.

The non-polio AFP rate was not correlated with the number of oral vaccine doses that were administered, countered the WHO Country Office in its response. The largest number of oral vaccine doses given in India was in 2004, which had the lowest non-polio AFP rate in the last eight years. Moreover, although the number of oral vaccine doses given in the country had shown a continuous decline since 2007, the non-polio AFP rate had increased during the same period. In Bihar and U.P. too, there were similar trends of reduced oral vaccine doses and rising AFP rates during 2007-2011.

“The ICMR [Indian Council of Medical Research] is leading the investigations into non-polio causes of AFP,” the WHO Country Office stated.

Polio eradication Polio free

Two years without polio 

The large sums of money spent in the eradication of the disease is an investment in the economic development of the country

In the 1980s, only three decades ago, 200,000 to 400,000 children, all under 5 years, were afflicted with polio paralysis annually in India. That was a daily average of 500 to 1000 cases. By the age of six, eight among 1,000 children already had polio paralysis; two would have died. In other words, one per cent of infants born were destined to develop polio. 

Global movement

In 1988, India joined the global movement for polio eradication — at a time when we had not even succeeded in bringing polio under control. Control status required at least 95 per cent reduction. In 1978, India launched the Expanded Programme on Immunisation (EPI) with BCG and DPT vaccines. The oral polio vaccine (OPV) was introduced the next year. Natural polioviruses are called ‘wild’ to distinguish them from vaccine polioviruses that constitute OPV. Vaccine viruses are ‘attenuated’ from wild viruses — which means they have lost most of their ‘virulence,’ the ability to cause paralysis and the ability to spread fast among children. These two are the dreaded qualities of wild polioviruses.

By 1988, diphtheria, whooping cough and neonatal tetanus had declined to control levels as a result of EPI’s efforts. But polio did not come under control — showing that OPV was not as effective in India as in the West or in China. There, just three or four doses protected all children. In India, we had to give many more doses for equal effect. From 1994, India began nationwide OPV campaigns (called pulse immunisation) — two per year — to give additional doses to all under-five children irrespective of the number of doses already given. That resulted in effectively controlling polio by 2000. One of the three types of polioviruses, wild type 2, was even eradicated by October 1999 when the average number of OPV doses had reached six per child. The type 2 component of OPV was not only more effective against that type, but it also inhibited the effect of types 1 and 3.

That left India with the struggle to eradicate wild types 1 and 3 using a blunt weapon, the trivalent OPV (tOPV), containing types 1, 2 and 3, which is necessary to attack all three viruses simultaneously. In the Gangetic plain States, particularly Uttar Pradesh and Bihar, 9-10 pulse immunisation campaigns were conducted annually from 2004 to 2010. We then developed OPV containing just type 1 to make the tool sharper against the type 1 wild virus. That is called ‘monovalent OPV’ (mOPV-1). Eventually, India made ‘bivalent OPV’ (bOPV) with types 1 and 3. Remember, we did not have wild type 2 virus since 1999. With new tools and covering almost100 per cent children in their homes, while travelling, in brick-kiln and sugarcane fields where temporary migrant labour set up homes, wild polioviruses had no place to hide. We succeeded in stopping the transmission of type 3 in 2010 and type 1 in 2011. The last child with wild virus polio was detected in Howrah, West Bengal, with the onset of paralysis on January 13, 2011. Since then, only bOPV has been used for immunisation campaigns in U.P. and Bihar, while tOPV is used in routine EPI and national pulse immunisation campaigns twice each year.

How sure are we that wild polioviruses have been totally banished? There is a solid body of evidence to show this. All hospitals and clinics that attend to sick children have been networked to report any illness that even remotely resembles polio. Such illness is called ‘acute flaccid paralysis’ (AFP). Stool samples from every child with AFP are collected and tested for the presence of polioviruses. Every poliovirus so detected is further tested to distinguish wild poliovirus from vaccine poliovirus. When a lot of OPV is given to children, many with AFP would have vaccine polioviruses. That is to be expected. Sewage samples are collected every week from several wards of Mumbai, Delhi, Kolkata and Patna. During 2011 and 2012, all sewage samples were consistently negative for wild polioviruses (but with plenty of vaccine viruses). In northern India, the last footholds of wild polioviruses, the second half of each year was the season of high wild virus transmission. We passed two ‘high seasons’ in 2011 and 2012 without a single case. India has truly succeeded, silencing the many prophets of failure.

Highly contagious

Wild polioviruses are highly contagious — illustrated by some 50 episodes of international importations to countries that had once eliminated them using OPV. We had exported wild viruses to Nepal and Bangladesh in our neighbourhood, and to Bulgaria, Angola, China and Tajikistan, to name some distant ones. Now India is polio-free and vulnerable to importation from Pakistan, Afghanistan and Nigeria — the three countries that have not yet eliminated wild polioviruses. We cannot lower our guard and must continue pulse immunisations as though importation is imminent. India has five points of border-crossing with Pakistan: two in Jammu-Kashmir, two in Punjab, and one in Rajasthan. At every point, individuals are given one dose of tOPV when they enter India.

What was very remarkable was that India’s money went into the lion’s share of expenditure for polio eradication in the country, thus easing up global funds for use in other countries that needed them more than we do. India spent about Rs 1000 crore every year since 2000. 

The rationale

Many have questioned the wisdom of spending such large amounts on one childhood disease. Was polio worth eradicating? From a humanitarian viewpoint as well as human rights angle no child deserved to be paralysed by a preventable disease. We know the struggle we had to go through merely to keep polio under control. Eradication is the best form of control. Once affected with polio, many children are neglected, do not complete high school, take up simple jobs like bicycle repair, managing telephone booths, etc.

The disability-determined productivity loss may be taken as about half of the gross domestic product per capita. That amounts to approximately Rs 50,000 per year; cumulated over 30 years of productive life, India was losing Rs. 15 lakhs per person — for a staggering Rs 45,000 crore per annum loss to the domestic economy from just one disease, polio, that affected 300,000 children each year. Controlling diseases that affect productivity is indeed a development activity. Eradicating polio is an investment. The absence of polio is both a measure of, and a means to, development.

The National Polio Eradication Certification Committee will confirm eradication of wild viruses and review the secure containment of laboratory storage of wild poliovirus strains or specimens likely to contain them before certifying India free of wild viruses. The Committee will wait for three years from the last virus detection before certification procedures, expected after January 2014. Thereafter, India will use only bOPV; later that will also be withdrawn, globally, synchronously. These rules of polio eradication ‘end game’ have been drawn up by the World Health Organisation and were endorsed by the World Health Assembly in 2012. In order not to create any polio immunity vacuum, the inactivated poliovirus vaccine will be introduced and sustained for at least five years. Polio eradication will then mean ‘no infection with any poliovirus, wild or vaccine.’

(The author was on the teaching faculty of Christian Medical College, Vellore, until retirement)