There has been a massive global investment in the fight against polio - over US$3 billion and countless volunteer hours.

The remaining 6 endemic countries are in Asia (India, Pakistan and Afghanistan) and Africa (Nigeria, Niger and Egypt).

Between 2003 and 2004, transmission halved in Asia (335 vs. 186) but more than doubled in Africa (448 vs. 1037).

An epidemic caused by a suspension of immunisation campaigns in Nigeria, and spurred by low immunity across the region, re-infected 12 previously polio free countries and re-established transmission in 5.

A large immunisation response from African countries in autumn of last year was hampered by conflict in Sudan, where vaccinators found it hard to reach children, and in Cote d'Ivoire, where campaigns were halted due to civil unrest.

The Africa epidemic continues to export the virus to polio-free countries, most recently into Saudi Arabia, demonstrating that 'polio anywhere is a threat to children everywhere'.

To close down the epidemic, 23 African nations will come together in 2005 to synchronise mass immunisation campaigns.