SEATTLE — The Bill & Melinda Gates Foundation announced Wednesday that it will spend $50 million — on top of $10 million already committed — to support emergency response to the Ebola outbreak in West Africa, marking the group’s largest donation to a humanitarian effort.

“It became clear to us over the last 7 to 10 days that the pace and scope of the epidemic was increasing significantly,” Chris Elias, president of global development for the world’s largest charitable foundation, told The Associated Press.

The Seattle-based foundation said the money will go to the United Nations, the World Health Organization, the U.S. Centers for Disease Control and Prevention and international organizations involved in fighting transmission of the virus.

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The money will be used to purchase supplies and to develop vaccines, therapies and better diagnostic tools. The foundation wants to help stop the outbreak as well as accelerate development treatments and improve prevention.

Elias said they have been talking to the foundation’s partners around the world to assess the best use of its dollars and could not say yet how much would be spent on the emergency response and how much on research and development.

“One of our key advantages is flexibility,” he said.

Global health and development dominate the work of the foundation, which has given away $30 billion since 1997. The foundation formed by Microsoft co-founder Bill Gates and his wife reported an endowment worth $40 million, as of March 2014.

The foundation was particularly influenced by the request on Friday by U.N. Secretary-General Ban Ki-Moon for $600 million to fight the Ebola outbreak.

Ki-Moon said efforts in the next few weeks would be essential to stopping the virus that has killed more than 2,000 people in Guinea, Liberia, Sierra Leone and Nigeria.

The foundation had previously committed more than $10 million on emergency operations, treatment and research. Of that money, $5 million went to the World Health Organization for emergency operations and research and development.

Another $5 million went to the U.S. Fund for UNICEF to support efforts in Liberia, Sierra Leone and Guinea to purchase medical supplies, co-ordinate response efforts and spread information.

Some of the $50 million will support strengthening existing health care systems in the countries affected by the outbreak, the foundation said.