To check the entry of the polio virus through migrant workers' children in the state, the Karnataka government, in coordination with the WHO and the UNICEF, is organising special pulse polio rounds across the state. Notably, this is two years after a two-year-old of a migrant labourer from Uttar Pradesh was diagnosed with polio in Bangalore.

The Regional team leader of WHO's National Polio Surveillance Project in India, Pavana Murthy recently said that the special rounds were to prevent the entry route for the virus through migrant labourers, especially from Bihar and Madhya Pradesh.

"Following the November 2007 case, 914 high-risk areas, including temporary settlements, construction sites, brick kiln huts, migrant population from these areas and beggars' groups, had been identified in and around the city for the drive," he said.

With 80 per cent of the country's polio cases reported from Bihar and Uttar Pradesh, health authorities are worried. "Considering that a large number of migrant workers from these two States come to cities such as Bangalore, Bellary (where a major outbreak was reported in 2003-2004), Hubli and other corporation areas, we plan to have a special round for children of migrant workers," Dr Murthy said.

About the new bivalent Oral Polio Vaccine (OPV), Dr. Murthy said that it would be introduced in the core endemic areas of western Uttar Pradesh and Bihar by January next year.

"The introduction of this vaccine in these high risk States in our next pulse polio campaign will help prevent the crippling disease in other non-endemic States," he said.

Health authorities were using the trivalent OPV to prevent all three polio viruses of Type 1, Type 2 and Type 3 across the country. However, after the eradication of Type 2 virus in 1999, they started using the monovalent vaccine (for eradication of Type 1). "The new vaccine will be able to eradicate both Type 1 and Type 3 viruses," he said.