Fifteen years ago, more than 1,000 children a day, in 125 countries across five continents, were being paralysed by polio.

The devastating effects of this incurable and deadly disease meant its very name struck fear into the hearts of millions across the world.

But by end of this year, health experts believe they could have eradicated polio from every country around the globe. A massive, last push in the international vaccination campaign should mean that the remaining six nations classified as having endemic polio - Nigeria, India, Pakistan, Niger, Afghanistan and Egypt - are declared free of the disease by next year.

If the goal is hit, it will be one of the World Health Organisation's (WHO) most stunning successes. In 1988, the 157 WHO members pledged to wipe out the disease. The success of the eradication programme is solely due to this 6p-a-time vaccine, which has been available in the West for 30 years, saving billions from death and disability.

But experts are now warning that one of the greatest public health achievements of this century could be hindered by a combination of Islamic radicals and a reluctance on the part of some of the richest countries in the world to put their money where their mouths are. Sources at the WHO have hinted that the future of the programme is being hampered by the fact that some G8 countries have pledged cash which has yet to materialise.

The WHO-led eradication programme is now facing a $200m (£110m) shortfall as it enters the most critical phase.

Immunisation levels in Nigeria, which accounts for 80 per cent of cases, have been hampered by a conspiracy theory propagated by Muslim extremists, that the polio vaccine is a Western weapon for sterilising women and spreading Aids.

A WHO spokeswoman said: "We are optimistic that the target will be reached but there is a big battle ahead over the next few months. It will not be easy."

Polio, short for poliomyelitis, can be caused by any one of three viruses which develop in the throat and intestinal tract of victims. It enters the body through the mouth, usually from hands contaminated with infected faeces - it thrives in unsanitary conditions and can spread rapidly through poor and developing nations.

It mostly affects children under three and remains contagious for up to six weeks. The virus attacks the nerve cells that control muscle movement, causing tiredness, fever and muscle pain. It can also invade the brain, choking the patient to death by paralysing the muscles used for swallowing, and frequently affects the spinal cord, causing partial or total paralysis. Victims can be left with disfigured or shrivelled limbs.

Until the latter half of last century, polio wreaked havoc across the world. An epidemic in New York in 1916 left 9,000 dead and 27,000 paralysed, while iron lungs for those whose breathing was affected were a familiar sight in hospitals throughout the 50s.

The breakthrough came in the 1960s, with the Oral Polio Vaccine (OPV), a live but weakened form of the virus, which could be given in drop form. It is particularly effective because not only does a dose of OPV immunise the person, but it also decreases the virus pool throughout the community.

The last case of "wild" polio (not caused by the vaccine) in the US was recorded in 1979. All 51 European states were certified polio free in 2002, meaning that three of the WHO's six regions - the Americas, the Western Pacific and Europe - have eradicated the disease. That has left the Eastern Mediterranean (which includes Pakistan), South-east Asia and Africa remaining with polio infection. Until the Nigerian crisis, the eradication programme had been impressed by the zeal with which the remaining endemic nations have attempted to hit this year's goal.

Western countries have for decades included polio immunisation as part of their childhood vaccination programmes, but developing nations do not boast the infrastructure to run such campaigns. These countries have opted for large, targeted initiatives several times a year in which millions of under-fives are immunised at a time.

Yesterday saw the end of a door-to-door initiative to immunise four million children in the Nigerian state of Kano in five days. Health workers administered a couple of drops of the vaccine into the mouths of every child under five. Samples were subjected to independent analysis to convince sceptics that it was safe, and health officials worked to persuade the Muslim clerics to their side. The initiative was given a boost when Ibrahim Shekaru, the Kano state Governor, administered the vaccine in the village of Takai at the start of the resumed immunisation initiative this week.

But last August, polio immunisation in the Islamic state was suddenly halted after a coalition of radical Muslim clerics and local politicians claimed that the vaccines were part of a Western plot to sterilise African girls and spread HIV/Aids. The effects were immediate and disastrous. Cases of polio in Nigeria increased from 50 to more than 250 within a year. At the beginning of last year, polio was endemic to two nations in sub-Saharan Africa; by this year, the Nigerian crisis was linked to re-infection in 10 more countries, including Chad, Ghana and Togo. The conspiracy theories about the vaccine spread to other Islamic states - Pakistan and Afghanistan.

Officials at the Global Polio Eradication Initiative, an alliance of the WHO, Unicef and other NGOs, looked on aghast as their dream of wiping out polio by 2005 appeared to be disintegrating before their eyes.

In 1989, when the eradication programme was set up, more than 350,000 people a year were developing polio. By last year, there were just 700 cases.

In January, the WHO called an emergency meeting in Geneva. Already faced with a $100m shortfall, officials felt they had no option but to commit an extra $100m to ensure 74 million children in Africa received a dose of OPV by the end of the year. If all goes well, the world could be declared to be rid of polio by 2008. But as a WHO official said: "That is only the beginning - there has to be the commitment to immunisation programmes if we want the world to remain that way."


1900: Polio virus identified

1921: Franklin D Roosevelt contracts polio

1954: First mass vaccine is developed

1979: Last case of wild polio is recorded in the US

1988: WHO launches global polio eradication initiative

1997: Last recorded case in Europe; the region is declared polio-free in 2002

2003: Kano, Nigeria, suspends vaccination after claims of a Western plot to sterilise Muslim world