International financial institutions are preparing funding packages for Liberia, Sierra Leone and Guinea hard hit by the deadly Ebola virus, development bank officials said on Monday as African leaders gathered for the first day of a U.S. summit.

African Development Bank President Donald Kaberuka told Reuters his institution would immediately disburse $50 million to the three countries where government resources and health systems are being stretched by the worst outbreak of the virus.

The World Bank is set to announce funding for each of the countries after approval by its board, bank officials said.

"We're putting together a substantial emergency package for the three countries and will announce it early this week," a bank official said.

The funding is part of a $100 million emergency response plan launched by the World Health Organization last week. WHO chief Margaret Chan has warned that Ebola was outpacing efforts to contain it and warned of "catastrophic" consequences if the situation deteriorated.

Sierra Leone and Liberia deployed troops on Monday under an emergency plan to fight the spread of the virus.

The latest outbreak began in the forests of remote eastern Guinea in February. On Monday, Nigeria's health minister reported a second case of Ebola in Lagos in a doctor who treated U.S. patient Patrick Sawyer, who died last month.

The impact of the outbreak and assistance for affected countries to try to contain it will be discussed on the sidelines of the African Summit attended by nearly 50 African leaders, U.S. official said.

The presidents of Liberia and Sierra Leone canceled their plans to attend the summit so they could deal with the virus at home.

U.S. President Barack Obama said on Friday the United States was "taking the appropriate precautions" and that some participants at the summit would be screened for exposure the virus.