The Bill & Melinda Gates Foundation said on Wednesday it would spend $50m (£31m) – on top of $10m already committed – to support the emergency response to west Africa's Ebola outbreak – the group's largest donation yet 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 Associated Press.
The Seattle-based foundation, said the money would go to the United Nations, World Health Organisation (WHO), US Centres for Disease Control and Prevention and other international organisations involved in fighting transmission of the virus.
The money will be used to purchase supplies and to develop vaccines, therapies and better diagnostic tools. Elias said they had been talking to the foundation's partners around the world to assess how best to use the money and could not say how it would be split between the emergency response and 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 $30bn since 1997. The foundation formed by Microsoft co-founder Bill Gates and his wife reported an endowment worth $40m, as of March 2014.
The foundation was particularly influenced by the request on Friday by Ban Ki-Moon, the UN secretary general, for $600m to fight the Ebola outbreak.
Ban 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 $10m on emergency operations, treatment and research. Of that money, $5m went to the WHO for emergency operations and research and development.
Another $5m went to the US Fund for Unicef to support efforts in Liberia, Sierra Leone and Guinea to purchase medical supplies, coordinate response efforts and spread information.
Some of the $50m will support strengthening existing health care systems in the countries affected by the outbreak, the foundation said.