Poliomyelitis is an acute viral infection caused by RNA virus of the family picornaviridae (1). It is primarily infection of the alimentary tract but may affect the CNS and in about 1% of cases may lead to paralysis and death (2). It usually affects children less than 5 years of age. Poliomyelitis was known to occur in pre-historic times and was seen in Egyptian mummies and paintings dating 3700 BC (3).
There are 3 serotypes of the wild polio virus – 1, 2, and 3 (3). Of all cases between January 2007 and June 2008, serotype 1 and 3 were detected in fecal samples of the AFP cases. No cases ascribed to serotype 2 has been detected anywhere in the world since 1999 (4,7).
Risk Assessment and Problem Statement
In the pre-vaccination era polio ravaged all countries of the world and no region was free of it. Since 1954, the vaccines were used extensively ushering in the vaccination era (5). This era in time saw implementation of some landmark eradication strategies. These measures on a global level helped in eliminating the disease from countries which successfully implemented their health policies. The polio endemic countries as of August 2008 were India, Afghanistan, Pakistan and Nigeria (6). Twenty five other countries reported cases of imported virus which were genetically traced back to those found in India or Nigeria (6).
During 2007, a total of 1,387 (1,315 were Wild Polio Viruses) confirmed cases were reported whereas in 2008 up to the month of November, a total of 1,449 WPV cases were recorded, worldwide (7). In India, while 874 cases were recoded in 2007, the number dropped to 532 in the year of 2008 upto the month of November. The majority of these cases hail from the states of UP and Bihar (7). It is obvious the situation has reached a stalemate with the number of new cases almost constant for some years and in some countries polio has even managed to stage a comeback, such as seen in the strife-torn Nigeria (9).
The Logic Behind Polio Eradication
Poliomyelitis was believed to be eradicable because man is the only host and a long term carrier state is not known to occur. The poliovirus is also relatively easy to detect because it causes a distinct, although not diagnostic, clinical entity—namely acute flaccid paralysis (AFP)— it is readily identifiable as a causative agent of the disease by simple laboratory tests, and, most importantly, it is easily controlled in endemic and epidemic situations by a widely available and affordable vaccine that leads to lifelong immunity (8). The vaccine is ideally suited for eradication programs as it interrupts the transmission of the WPV by multiplying the in the intestine. It mimics the natural history of infection of the WPV and can also be transmitted through a recently vaccinated child to close contacts around him who are not immunized. The half life of the excreted virus is 48 hours in the sewage and spread can occur in that period.
After the initial euphoria of success with the smallpox eradication, polio became the next logical vaccine-preventable disease to be targeted for eradication – both because of the morbidity caused by the disease and the theoretical eradication potential of the vaccine. Launched in October 1988 by the 41st World Health Assembly (WHA Resolution 41.28), the Global Polio Eradication Initiative aimed to eradicate poliomyelitis from the planet by the year 2000. It is the largest international public health initiative ever undertaken, costing several billion dollars and immunizing billions of children worldwide. It has also been mired in controversy almost since its outset (9).
The initial target date, 2000, unfortunately came and went without eradication in sight. So too did the next scheduled date of 2005 (a target set by Rotary International, the most important non-governmental supporter of the Global Polio Eradication Initiative). As yet no future target date has been set (9).
What is Being Done? – The WHO and Indian Perspective
The Global Polio Eradication Initiative has been spearheaded by the World Health Organization (WHO), Rotary International, and the US Centers for Disease Control and Prevention (CDC) and UNICEF and it aimed at polio eradication by 2000 (6).
There are four core strategies to stop transmission of the wild poliovirus in areas that are affected by the disease or considered at high risk of re-infection (6):
1. High infant immunization coverage with four doses of oral poliovirus vaccine (OPV) in the first year of life.
2. Supplementary doses of OPV to all children under five years of age during Pulse Polio Sessions.
3. Surveillance for wild poliovirus through reporting and laboratory testing of all acute flaccid paralysis (AFP) cases among children under fifteen years of age.
4. Targeted “mop-up” campaigns once wild poliovirus transmission is limited to a specific focal area.
The strategy, as with smallpox, aims to achieve maximum vaccine coverage to terminate the circulation of the virus in the population coupled with a reliable surveillance tool for the detection of remaining pockets of virus circulation and to monitor progress. Herd immunity is achieved with high routine vaccine coverage (at least 90% for all 3 doses) (10).
This primary strategy is supported by mass immunization programmes (immunising all infants less than 5 years of age independently of the routine immunisation programme on a single day or few days) – this is known as the Pulse Polio Programme in India (11). Most endemic regions and countries follow the MIPs with Mop Up programmes which locate all the cases missed during the MIP rounds. The viral spread is measured in terms of the Acute Flaccid Paralysis Rate in children less than 15 years of age. In the eventuality of a case detection, the index case is surrounded with an immunization ring to restrict the spread of the wild virus (12).
Surveillance forms a major component of the eradication campaign. A laboratory network co-ordinated by the WHO and consisting of over 125 laboratories throughout the world has been established, and is organized in three levels–national laboratories for virus isolation and preliminary characterization, regional reference laboratories for confirmation and more specialized testing and specialist laboratories (12).
Why are These Measures Unsuccessful?
While it is a general consensus that the apparent plateau in the eradication campaign is multifactorial in causation, it is a known fact that different factors are of relative importance in different countries. Arguably, one of the most important pull downs is campaign fatigue that has set into the GPEI’s implementation. This is almost universal in all the endemic nations, especially India and Nigeria (9).
In Pakistan, it as been attributed to outright refusal by parents and shortage of female health workers. The situation is made worse by the security situation in some regions such as the Swat valley where the vaccinators are not able to even reach. These conflict ridden areas are reporting an increasing number of new polio cases (13).
In a calamitous setback in mid-2003, Nigeria’s northern states halted the vaccination campaign for a year after politically fuelled rumors swept the region that the vaccine contained the AIDS virus or was part of a Western plot to sterilize Muslim girls. Within a couple of years, 18 once polio-free countries have had outbreaks traceable to Nigeria. Though most have since been tamed, Indonesia and Nigeria itself remain major worries (14,15).
The situation is similarly bleak in India, a country which is tantalizingly close to eradicating the disease. The enormous population load, dense living conditions, an inadequate public health sector and illiteracy have acted as the banes of the eradication drive. Health workers have repeatedly reported being turned away from homes by mothers who felt that the government was not doing enough for their children (14). On the other hand, Afghanistan continued to suffer from the disease’s march during the recent war on its soil, with civic amenities and health services falling to a dismal low. Ongoing conflicts have had a major impact on the polio eradication in the endemic countries, with immunization teams being hampered from reaching out. In a number of situations the vaccines have been spoilt, whole stocks in total because of the improper storage facilities.
The situation in the Uttar Pradesh state in India has worsened in recent time mainly because of the falling vaccination cover and in Bihar because of increasing parental resistance. This has been noticed despite exemplary efforts on part of the government and the local authorities to step up the campaign (16). Even more problematic here has been the difficulty in achieving successful immunisation, despite multiple rounds of vaccination, because of very high population density, crowding and high levels of diarrhoeal disease interfering with the immunogenicity of the oral polio vaccine (17).
In recent times, probably the most worrying of all problems in polio control has been the poor migration control between endemic and non endemic regions. The stark example was the reporting of a case of polio from Karnataka state in India, which had reported no case of the disease in nearly three years. The case was traced back to a contact in Uttar Pradesh state putting in the spotlight on as to how important it is to have proper migration controls in place.
Finally, in contrast to smallpox, what complicates polio eradication is the much greater difficulty in recognition of infection despite the occurence of AFP. The great majority (>99%) of infections are asymptomatic, greatly complicating surveillance and monitoring (9).
New Indian Initiatives
Even though efforts for eradication has been given up with respect to most diseases (19), especially tuberculosis and leprosy, the goal of the National Polio Surveillance Project, India, stays firmly on the lines of the international Polio Eradication Initiative – and that is to completely eradicate polio so that “no child will ever again know the crippling effects of polio.”(18).
The collaboration has set the following goals to make sure that the eradication drive succeeds (20):
1. Maintaining the Acute Flaccid Paralysis detection target at >1 case per 100,000 population.
2. Maintaining the completeness and time accountability of the AFP reports impeccably at 90% and 80% respectively.
3. Investigating the reported AFP cases within 48 hours in >80% cases.
4. Collection of stool samples from reported cases in < 14 days in more than 80% cases.
5. Follow-up exam of the reported cases at least 60 days after paralysis onset to verify the presence of residual paralysis or weakness (Target > 80%).
6. Confirming the arrival of specimens at the national laboratory < 3 days of being sent (Target > 80%)
7. Confirming the specimens arriving at the laboratory in “good condition” (Target > 80%)
These measures are in addition of the four main ones defined earlier.
A lot has changed since the world leaders in health decided to eradicate Poliomyelitis from the world. The achievable target was pushed back out of reach due to a number of practical problems. With the Polio Eradication Initiative working at full swing in the nations with the residual polio cases, the eradication of this debilating disease is not far away but a few challenges remain to be overcome before this can occur.
Viren Kaul is a TLS RA and final year student at Sir Ganga Ram Hospital in Delhi, India
Vindhya Palled is a medical student at the Karnataka Institute of Medical Sciences in Hubli, India
Jishu Kaul is a medical student at Dayanand Medical College in Ludhiana, India
1. Wikipedia – Poliovirus: http://en.wikipedia.org/wiki/Poliovirus
2. Encyclopedia Britannica: http://www.britannica.com/EBchecked/topic/467378/polio
3. eMedicine – Poliomyelitis, S Vidyadhara et al – http://emedicine.medscape.com/article/1259213-overview
4. Park and Park text book of preventive and social medicine – Bhanot publications.
5. Wikipedia – Polio Vaccine: http://en.wikipedia.org/wiki/Polio_vaccine
6. WHO: Programmes and Projects: Media Center: Poliomyelitis: http://www.who.int/mediacentre/factsheets/fs114/en/index.html
7. WHO annual bulletins 2007 and 2008.
8. The Lancet Infectious Diseases, doi:10.1016/S1473-3099(04)00999-5.
9. Eradication of disease – the case study of polio, South African Medical Journal, Nov 2007, Barry D. Schoub. (http://findarticles.com/p/articles/mi_6869/is_11_97/ai_n28533884/)
10. Data courtesy: GPEI. (http://www.polioeradication.org/content/fixed/national.shtml)
11. Pulse Polio Immunization Campaign, Government of India (http://www.health.mp.gov.in/ppip.HTM)
12. National Polio Surveillance Project, a Government of India and WHO collaboration. (http://www.npspindia.org/Surveillance%20Strategy.asp)
13. OneWorld South Asia – Insecurity hampering polio eradication in Pakistan – October 10th, 2008. (http://southasia.oneworld.net/todaysheadlines/insecurity-hampering-polio-eradication-in-pakistan)
14. The New York Times – Rumor, Fear and Fatigue Hinder Final Push to End Polio – March 20th, 2006. (http://www.nytimes.com/2006/03/20/international/asia/20polio.html?pagewanted=print)
15. Jegede AS. What led to the Nigerian boycott of the polio vaccination campaign? PLoS Medicine 2007; 4: 0001-0006.
16. Wild poliovirus weekly update. Global Polio Eradication Initiative. 30 May 2007. http:// www.polioeradication.org/casecount.asp (last accessed 4 June 2007).
17. John TJ, Shah NK, Thacker N. Indian Academy of Pediatrics and Polio Eradication in India. Indian Pediatr 2006; 43: 765-768.
18. National Polio Surveillance Project – A government of India – WHO collaboration – http://www.npspindia.org/index.asp
20. NPSP, India – http://www.npspindia.org/WHO%20indicators.asp – Eradication targets.