Waiting in line: Indonesia stepped up vaccinations after a Nigerian poliovirus paralysed four children. Credit: DADANG TRI/REUTERS

Polio is spreading to countries previously considered free of the disease, following a vaccine boycott in Nigeria in 2003. An outbreak in Yemen has sparked fears of an epidemic in the poorly immunized Middle Eastern nation. And the virus has now reached southeast Asia, with four cases confirmed in Indonesia last week.

Polio has not been seen in Yemen and Indonesia for a decade. Genetic analysis shows that the virus appearing in both areas is similar to the one that caused a 2003 outbreak in Nigeria. Polio vaccines were rejected in northern Nigerian states after Muslim clerics claimed they had been contaminated with HIV and contraceptives. Sixteen ‘polio-free’ countries have reported cases since 2003.

“The recent outbreaks can be traced back to that boycott,” says Arun Thapa, an adviser on polio eradication in southeast Asia for the World Health Organization (WHO), based in New Delhi.

In April, the WHO confirmed 22 cases in Yemen, and health officials anticipate further infections because of low immunization rates among the nation's children. “We expect there will be many times this number,” says Mohamed Wahdan, the WHO's Eastern Mediterranean polio adviser.

Middle Eastern nations have been on high alert for polio since December 2004 and many have already started preventative vaccination programmes. “Unfortunately, the virus spread ahead of the campaign in Yemen,” says Wahdan. “We hope to be ahead of the virus in other regions.”

This month, Yemen will initiate a house-to-house campaign to vaccinate all its 3 million children under 5 years of age. Health officials are using a polio vaccine specifically targeted at the virus responsible for the outbreak, which they say provides greater immunity with fewer doses. “We believe it is the best tool in the face of an epidemic,” says Wahdan.

In Indonesia, health officials are confident the virus can be restricted to the small villages in West Java where the four cases were reported. “The immunization level in Indonesia has been good, with 95% coverage of children,” says Bardan Rana, the WHO's immunization officer in the country. But officials are taking no chances and are giving supplementary immunization to 5.2 million children under the age of five in West Java and surrounding provinces.

Although the recent outbreaks do not bode well for the eradication of polio, Thapa says he is more concerned about the situation in India. “It is the largest polio-endemic country and has been a source of wild poliovirus for other countries in the past.”

Officials suspect the virus travelled to southeast Asia through Saudi Arabia, a popular destination for Indonesian workers and Muslim pilgrims. “As long as there is polio is in the world and a lot of travel, we expect the virus to be imported,” says Rana.