Doctors fighting the crippling disease polio are armed with powerful weapons and are certain they have the right strategy. Yet they cannot seem to crush the final bastions of resistance. More than US$4 billion has been poured into the battle since 1988, when leading health organisations made eradicating polio their top priority. They knew it was not impossible because eight years earlier, after a pioneering campaign, the world was for the first time declared free of a disease - smallpox. They have made impressive gains, but as the re-emergence of polio in Indonesia and Yemen last month proved, nothing is certain in the struggle against viruses. A 2000 target for eradication has been put back to the end of this year, but this also looks like being missed. One of the problems for medical workers is their own success - eradication has been so dramatic in some areas that immunisation is being ignored. But politics is also getting in the way. In August 2003, Nigeria's northern Muslim states stopped vaccinating children because of rumours that oral doses had been contaminated by the United States with HIV and substances that would cause sterilisation in girls. After intense international lobbying, the programme resumed 10 months later, but by then the disease had spread. The World Health Organisation's polio chief, David Heymann, said that after this setback in Nigeria, 22 countries had had to tackle the disease, whereas before there had been just six where infection was endemic - the West African nation, India, Pakistan, Afghanistan, Niger and Egypt. 'As a result, polio has spread from Nigeria through west and central Africa into the Middle East and as far as Indonesia,' Dr Heymann said from his Geneva office. 'There are now an additional six countries that have endemic polio, which means it is transmitting within those countries.' He said the 10 countries where outbreaks did not become endemic staved it off by increasing vaccinations through national campaigns. Millions of people succumbed to polio in the early 1950s. They were confined to iron lungs and wheelchairs as it attacked respiratory systems and spread to spinal chords and brains. Between 10 and 20 million people around the world are thought to be sufferers of the disease. The creation of a vaccine through injection by American Jonas Salk in 1954 broke the cycle of misery and has been hailed as one of the landmark medical achievements of the 20th century. Seven years later, the more easily administered oral vaccine was unveiled and the complementary medications, with minor modifications, have reduced infections to stunningly low levels. When the Global Polio Eradication Initiative was launched 17 years ago by a coalition of the WHO, United Nations Children's Fund, Rotary International and the United States Centres for Disease Control and Prevention, more than 350,000 new infections were being recorded each year. By 2003, intensive advertising and immunisation programmes had cut that to just 784, although last year the number rose to 1,267. More than 200 cases have been identified so far this year, although that is likely to rise with outbreaks in Indonesia and Yemen and with the peak period for concern - the monsoon rains beginning in August - still ahead. Polio is transmitted through contaminated food and water or contact with the faeces of an infected person. It is highly infectious and can attack the central nervous system, sometimes resulting in paralysis or death. Sufferers are mostly children under five. Infection is often mild and causes no symptoms, or a sore throat and slight fever may develop within three and 21 days. When severe, it may cause inflammation of the brain and spinal chord, with severe headache, neck stiffness and backache. The most telling signs are paralysis of an arm or leg or difficulty in breathing due to respiratory muscles being affected. Vaccination, particularly of babies, has meant its disappearance from much of the developed world. The last case in the US was in 1979, Britain in 1982 and Hong Kong 20 years ago. The global initiative has made great gains, with the Americas being declared polio-free in 1994, the western Pacific in 2000 and Europe in 2002. Efforts to rid the world of the disease stem from a pilot programme run in the Philippines by the non-government service organisation Rotary International in the late 1970s. Spokeswoman Vivian Fiore said the successful vaccination of 6 million children led to the ambitious aim of protecting all the world's people In 1985, Rotary founded PolioPlus, which aimed to immunise all the world's children this year, Rotary's centenary. 'This convinced the World Health Assembly to adopt polio eradication as a goal,' Ms Fiore explained from Rotary's Chicago headquarters. The global initiative was set up in 1988. Rotary's volunteers have since immunised 2 billion children in 122 countries. But Unicef polio programme chief Maria Costales is worried that governments are not ensuring their citizens remained immunised. 'The bottom line is that we need to reach all children under the age of five and immunise them with the oral polio vaccine in endemic countries,' Dr Costales said. 'We also need to ensure that there is continuing immunisation in polio-free countries.' She was sceptical that in some countries adequate campaigning was being done to have parents vaccinate their children, or that proper dosages were being given with the oral vaccine - favoured by developing world governments because it is inexpensive and easy to administer. 'All that's needed are two drops to protect a child, at the necessary intervals four times during the first year,' she said. 'But sometimes simple things are difficult to grasp.' Lack of immunisation is the reason eight cases have emerged in Indonesia since April 26, when an 18-month-old girl was confirmed as having polio - the first time the disease had been detected in the country since 1995. All the cases are in Sukabumi district, just southeast of the capital Jakarta, and are thought to have originated from Saudi Arabia, either from a migrant worker or a Muslim pilgrim to the holy city of Mecca. An African, most likely from Nigeria, is believed to have passed the disease on. To prevent the disease from spreading, an immunisation drive involving more than 5 million children is being launched this month. WHO Indonesia representative George Petersen believes the increased surveillance and vaccinations will ensure the disease is kept under control. That it had been detected so quickly proved that surveillance systems were working well, he said. But he cautioned: 'Indonesia is still located among countries that have endemic polio - India and Pakistan and of course there's also Africa. As long as there are endemic countries, the virus could be introduced.' Africa is also claimed to be the source of the Yemen outbreak. There, at least 63 people have been diagnosed with polio and experts say the number could reach 100 before it is brought under control. Experts suggested that even though a more difficult situation existed in Africa now than a year ago, the outlook for eventually meeting eradication targets was positive. Dr Heymann said the new emergencies had meant the global partnership had dipped into its US$25 million reserve fund, above and beyond its US$600 million annual budget. With the ongoing alerts, an extra US$50 million would be needed from donor nations. But the WHO has high hopes of a new vaccine developed by two Indian companies, already being used in the country's crowded slums, in Yemen, from next month in Egypt and, soon, Indonesia. 'Right now, we believe India, Pakistan, Afghanistan and Egypt will finish with polio by the end of the year if this new vaccine has the effect that we believe it will have,' Dr Heymann said. The deputy director of the global immunisation division of the Atlanta-based Centres for Disease Control and Prevention, Bob Keegan, is concerned about Africa. Eradication targets were ambitious, given that polio was prevailing in countries with some of the world's poorest people, worst sanitation and most difficult political conditions, as well as civil unrest and other problems. While such problems persist, there is little chance that polio will go the way of smallpox. But that moment is tantalisingly close. When is up to governments. The wealthy ones need to provide the funding and the poorer ones the will.