BISSAU — Guinea-Bissau has decided to close its frontier with eastern neighbor Guinea in a bid to prevent the entry of the deadly Ebola virus, Prime Minister Domingos Simoes Pereira said.

The disease has killed more than 1,000 people in Guinea, Liberia and Sierra Leone in the world's worst outbreak of Ebola, and the World Health Organization has called it an international emergency. Three people have also died in Nigeria.

"Guinea-Bissau has decided to close its border with Guinea-Conakry from Aug. 12 given the threat of the Ebola virus," Pereira told a news conference late on Tuesday.

The order will likely mean the closure of official road border points, but it will be difficult to police the long and porous frontier in rural areas away from formal highways.

Governments have taken a range of measures to prevent the spread of Ebola across international borders.

Ivory Coast on Monday banned air travelers from the three worst-hit countries, while Ghana on Tuesday postponed the start of the academic year for at least two weeks at universities and colleges to allow screening measures to be put in place.