As the U.S. government and the United Nations both stepped up giving Wednesday to quell the Ebola epidemic sweeping through several West African countries, the Bill and Melinda Gates Foundation announced it will spend $50 million on the international effort seeking a vaccine and other therapies.

The United States donated five ambulances Wednesday to help Sierra Leone's fight against Ebola as the West African government acknowledged it can take up to 24 hours to pick up bodies in the spiraling crisis.

The Bill & Melinda Gates Foundation's donation is the U.S.-based group's largest to a humanitarian effort. The $50 million includes $10 million the foundation previously committed for emergency operations, treatment and research. The money will be used to purchase supplies and to develop vaccines, therapies and better diagnostic tools.

More than 2,200 deaths throughout West Africa have been attributed to Ebola amid the worst outbreak of the disease in history. The sick have been using motorcycle taxis and other public transport to get to hospitals, further increasing the risk of transmitting the disease that kills about half its victims.

Kathleen FitzGibbon of the U.S. Embassy in Sierra Leone handed President Ernest Bai Koroma the keys to five ambulances Wednesday. The U.S. has spent more than $100 million responding to the outbreak.

"Together we will win this fight," Koroma told her.

Sierra Leone, Liberia and Guinea — the three countries hit hardest by the outbreak — are also in need of more protective gear for health care workers and more treatment beds for Ebola victims. The World Health Organization says about 1,000 more beds in isolation centers are needed.

Also on Wednesday, the United Nations allocated $3.8 million from an emergency fund to support a U.N. air service operating in the Ebola-struck region. U.N. humanitarian chief Valerie Amos said reduction in commercial air flights as a result of the outbreak has hindered the deployment of health workers and supplies.

Doctors Without Borders has said bodies are being left to rot in the streets of Sierra Leone, a claim the country's health officials have rejected. But Ibrahim Ben Kargbo, an adviser to the president, did acknowledge that it can take up to a full day to retrieve a dead body because it must first be tested for Ebola.

Ebola is transmitted through bodily fluids. Dead bodies are particularly contagious and must be buried with extreme care. Experts say traditional burials that wash the dead have been a significant source of Ebola transmission.

Senegal, meanwhile, announced that its only confirmed Ebola patient has recovered. But Dr. Moussa Seydi told Senegalese radio the young man is still suffering psychologically after losing several relatives to the disease.