The girl is believed to have contracted the virus from neighbouring southern Sudan, which has struggled to improve its health sector since a 2005 peace deal ended a two-decade civil war.

Shahnaaz Sharif, Kenya's director of public health and sanitation, said a vaccination campaign would begin in the area on March 7 and would aim to immunise more than 95,000 children.

Youngsters under three are most at risk from the disease, which can cause irreversible paralysis. Vaccines have eliminated the virus as a public health threat in most parts of the world.