The polio outbreak in Indonesia is still spreading and could pose a global health threat, the United Nations children's agency Unicef has warned.
The polio virus mainly affects children
Unicef spokesman David Hipgrave said Indonesia's size and its large number of migrant workers meant the virus could spread further afield.
About 225 cases of polio have been confirmed in five Indonesian provinces since the outbreak began in April.
Another round of mass vaccinations is due to begin at the end of this month.
"Because it's such an enormous country, because the outbreak has been quite substantial... there's an enormous concern that if the virus is established here [it] will become an exporter of the virus to other countries, in the region or globally," Mr Hipgrave told the French news agency AFP.
Labourers and fishermen travelling to other neighbouring countries, such as Malaysia, the Philippines and Thailand, could take the virus with them, he warned.
"People are very concerned that if the virus is re-established here it will become a regional risk and potentially a global risk," Mr Hipgrave said.
He also warned that the waterborne disease could spread more easily during the wet season, which usually starts in October.
"The wet season is approaching in Indonesia in a month or two, when waste is less efficiently dealt with," Mr Hipgrave told reporters.
"There's a higher risk that water supply for a broad of range of communities will be contaminated with the virus."
Traced to Africa
Indonesia first detected polio in West Java province, 120km (75 miles) east of the capital, Jakarta, in April.
Before that, the disease had been eliminated from Indonesia for nearly 10 years.
Officials believe the outbreak can be traced to Nigeria, where vaccinations were suspended in 2003 after radical clerics said they were a US plot.
Indonesian officials say the virus could have been picked up by a pilgrim on the hajj to Mecca, or by a migrant worker.
A countrywide vaccination drive is planned for 30 August, to be followed by another on 27 September.
Unicef, together with the World Health Organization, is responsible for the upcoming campaigns, as well as two previous immunisation rounds carried out in May and June - each reaching about six million children.
The Indonesian outbreak is a major setback to UN plans to eliminate the disease by the end of 2005.