As the worst-ever Ebola epidemic rages on in Africa, President Barack Obama announced Tuesday that the US will ramp up efforts to combat the the virus as part of "the largest international response in the history of the CDC."

In an address from the Centers for Disease Control and Prevention headquarters in Atlanta, Obama said that the US is willing to take the lead on international efforts to combat the virus. Ebola "is a global threat, and it demands a truly global response," Obama said.

"This is an epidemic that is not just a threat to regional security. It's a potential threat to global security, if these countries break down, if their economies break down, if people panic," he said. "That has profound effects on all of us, even if we are not directly contracting the disease." This outbreak is already "spiraling out of control," he added.

The speech came amid increasing criticism that the international community has not responded quickly and boldly enough to what has become the worst Ebola outbreak in history. And Obama's words at the CDC were more alarming and urgent than his previous comment on Ebola in August, when he emphasized that the disease is one that strikes under-funded health systems.

"The reality is this epidemic is going to get worse before it gets betteR."

So far, more than 2,400 people have died this year from Ebola — more than the combined total of all previous outbreaks since the first recorded in 1976 — and the epidemic has spread to five African nations, including Guinea, Sierra Leone, Liberia, Nigeria, and Senegal.

Experts at a senate hearing on Tuesday said that the actual death toll is much higher, and that without effective actions to stop it, the case load will grow into the hundreds of thousands. More cases, they cautioned, will mean more potential for Ebola spread beyond Africa.

"The reality is this epidemic is going to get worse before it gets better, but right now," Obama said, "the world still has an opportunity to save countless lives. Right now the world has a responsibility to act, to step up, to do more."

3,000 troops dedicated to fighting Ebola

To turn the outbreak around, the White House has committed more than $175 million to what it's calling a "top national security priority."

The focus of the funds is stopping spread in West Africa. The US will send more than 3,000 troops to the most affected areas, and set up a joint operation in Monrovia, Liberia — the hardest hit of the five regions — to coordinate relief efforts.

In addition, the plan will boost the number of health workers and health-care centers in the region. The US pledged to build as many as 17 additional Ebola treatment units — with a total of about 1,700 beds — and to help recruit medical personnel to staff them. (Right now, people in Liberia are being turned away from treatment facilities because there is no capacity to care for them.) The Department of Defense also plans to establish a site where up to 500 health care providers can be trained each week.



USAID will also support a program of distributing kits with sanitizers and medical supplies to some 400,000 of the most vulnerable households in Liberia.



The Obama administration has asked Congress for an additional $88 million to combat Ebola, including $30 million to send more relief workers and lab supplies from the CDC and $58 million to invest in the development of the experimental Ebola drug ZMapp and two vaccine candidates.

Chances of Ebola spread in the US "extremely low"



Despite the alarm about the situation in Africa, the White House continues to quell worries about Ebola in America. President Obama said the chances of Ebola spreading in the US are "extremely low."



"US health professionals agree it is highly unlikely that we would experience an Ebola outbreak here in the United States, given our robust health care infrastructure and rapid response capabilities," reads a fact sheet from the administration.



"Nevertheless, we have taken extra measures to prevent the unintentional importation of cases into the United States, and if a patient does make it here, our national health system has the capacity and expertise to quickly detect and contain this disease."

Ebola toll could rise to "hundreds of thousands of cases"



At a Tuesday Senate hearing on Ebola in West Africa, health officials who have been working on the front line of this epidemic said that if the world doesn't act now, it's only a matter of time before cases start turning up on shores outside of Africa.

Beth Bell, director of the National Center for Emerging and Zoonotic Infectious Diseases at the CDC, said that the number of Ebola cases could balloon into the "hundreds of thousands" without effective interventions.



Anthony Fauci, director of the National Institute for Allergy and Infectious Diseases, said budget cuts at his agency can be partly to blame for the slow response to the outbreak. The lack of funding "eroded, in insidious ways, our ability to respond in the way I and my colleagues would like to respond to these threats." He also said it's very unlikely that the virus will mutate to become airborne, though he couldn't rule it out given biology's unpredictability.

Too little, too late?

The American Ebola survivor Kent Brantly, who contracted the virus while working as a medical missionary in Liberia, criticized the "painfully slow and ineffective" response to the outbreak, and noted that the international community only seemed to wake up to Ebola in July, after he and his colleague Nancy Writebol got infected.

"Many have used the analogy of a fire burning out of control to describe this unprecedented Ebola outbreak. Indeed it is a fire-a fire straight from the pit of hell," he said, with his wife seated next to him.

"We cannot fool ourselves into thinking that the vast moat of the Atlantic Ocean will keep the flames away from our shores." He called on more investment in Ebola "to keep entire nations from being reduced to ashes."

A worst-case scenario

Dr. Bell painted a picture of a best and worst case scenario for this outbreak. "The best case scenario is that over the coming months we're able to effectively isolate and treat Ebola patients, we're able to effectively trace all their contacts to make sure they're all followed for 21 days, we're able to do something about safe burial practices so we don't have bodies in the streets." Eventually, she said, we'll see the caseload decrease.

"In the worst case scenario, we continue to see an exponential rise in cases that we're currently seeing. And an important corollary to that is exportation to other countries." She noted that the outbreak that originated in Guinea in December has already spread to Liberia, Sierra Leone, Nigeria and Senegal. "You can imagine the outbreak spreading outside the borders as part of a worst-case scenario."

Learn more about why this Ebola outbreak became the worst we've ever seen in our 2-minute Vox explainer