Aid officials say a surge of international support since last fall has helped contain the Ebola outbreak in West Africa, but as U.S.-built clinics sit dormant amid a fading health crisis, the question remains: what happens to the billions of dollars' worth of U.S. resources committed to the region?

Next month, Fox News is told, the U.S. military plans to end its Ebola response mission, gradually withdrawing the remaining 1,300 troops. As of Jan. 5, the Defense Department had spent $385 million on Operation United Assistance since October.

The military mission was designed as a temporary assignment. But some observers wonder what will happen to the $2.6 billion earmarked for the State Department and USAID for the Ebola Response and Preparedness Fund, announced in November. They question whether the aid was disproportionate to the actual threat, and if there is a risk of sustained spending where it is not needed.

"We as a nation were certainly caught flatfooted in the Ebola crisis, so certainly you can understand the efforts" to send aid and to beef up vaccine research domestically, said Steve Ellis, vice president of Taxpayers for Common Sense, a government watchdog group based in Washington.

However, "the only concern we have is when you are talking about a disaster or an epidemic, [the] response from Congress and the public is always, 'quickly, throw a lot of cash out.' But in reality, it might be more appropriate to mete out the money over time where it can be flexible and we have some oversight," Ellis added.

There have been 22,500 confirmed cases of Ebola and nearly 9,000 deaths reported in West Africa as of Dec. 31, according to the World Health Organization (WHO). This is significantly lower than early estimates that warned if there was no coordinated response, more than a million could be infected by the end of January.

An infusion of international aid beginning in September helped reverse the tide, aid officials said, through new treatment centers, aggressive safety protocols for health care workers, and education. The number of new cases in the hardest-hit countries of Liberia, Sierra Leone and Guinea plummeted from a peak of 1,000 a week to around 100 a week by the end of January.

Recent reports in The Washington Post say while U.S. aid was instrumental in building new clinics, some centers haven't been used since the downturn in infections. A stalled U.N. effort to distribute home-health care kits reportedly has resulted in "most of the supplies sitting in unopened boxes across the country."

Chris Coyne, an economics professor at George Mason University and author of "After War: The Political Economy of Exporting Democracy," says it is difficult to know whether funds are still being spent wisely, or if they ever were. In crisis-related events, he noted, "the incentive is to get money out of the door" and "oversight is a tertiary concern."

A U.S. defense official who works closely with U.S. Africa Command (AFRICOM) told Fox News the money is essentially going to be channeled through the U.S. government to NGO's (non-governmental organizations).

"We built a bunch of Ebola Treatment Units (ETUs) which was essentially the only mission. Now it's for the NGO's and other agencies to [operate] them. Though, as I understand it, they're barely being used," the official said.

"Part of my concern, is the lack of accountability for all this money," the official said. "USAID doesn't use its own people. They've just become project managers of money they throw to NGO's."

The Centers for Disease Control and Prevention (CDC) has 214 staff in West Africa, while the U.S. government is fielding a total of 10,000 personnel -- the vast majority African nationals under contract, according to reports.

The State Department would not supply FoxNews.com with current levels of spending, nor would it estimate how much of the designated funds have been used since the crisis began. However, a department official suggested that, like others operating in the region, the U.S. is not ready to declare victory over the disease just yet -- suggesting the aid still is being put to good use.

"The downward trend of cases is encouraging," the official said. "But it is important to stress that still we need everyone to remain vigilant and persistent as we continue the push to get to zero cases."

Indeed, the target is "zero," and so far, that number has been elusive. While some new clinics might remain empty, even newer mobile treatment centers are responding to "hot spots" that continue to flare up in remote villages and slum areas at a pace they could not achieve before, aid officials told FoxNews.com.

Dr. Peter Salama, UNICEF's global Ebola emergency coordinator, told FoxNews.com while the total number of cases has declined, the pathogen is a sleeping beast. In fact, for the first time since the downturn, he said, the rate of infection actually went up the first week of February, after a long period of decline.

According to the WHO, Sierra Leone registered 80 of the 124 new cases that week. There were 39 in Guinea and five in Liberia.

"We have seen this before -- the number of cases begin to go down, and then they [go] back up again -- no country will be safe until we get to zero," he said.

UNICEF -- which receives USAID funding -- has been instrumental in setting up "Community Care Centers," which range from elaborate triage tent facilities that were set up in Sierra Leone during the worst of the outbreak, to the more permanent dual-use clinics that will serve as long-term health care centers in Liberia, where entire hospitals had shuttered during the crisis. UNICEF spent more than $200 million to date in the region, according to Salama, and is just one of over 60 major aid organizations listed on the USAID website as partners in the Ebola response and relief efforts.

Salama said UNICEF will continue to build new clinics in an effort to improve public health and social services for the poverty-stricken region. They also are addressing malaria outbreaks and other infectious diseases, and finding homes for more than 15,000 Ebola orphans, he added.

"There were periods [in the history of Ebola outbreaks] where cases began the decline," he said, "and the community, the government, the international partners begin to relax a bit, only to have it come back even stronger than before."

Today, Salama added, "all it takes is one unsafe funeral, one sick person, and you end up with another flare."

Coyne and the others acknowledge it is unrealistic to expect the USAID to track every dime in these remote hot zones. But the agency's own record of monitoring its contractors and NGO's has been called into question on numerous occasions; most recently in January, when it was forced to suspend one of its largest nonprofit contractors, International Relief and Development (IRD), headquartered in Arlington, Va.

The firm won $2.7 billion in U.S. contracts since 2007, mostly for reconstruction in Afghanistan, but was accused of mischarging the government while paying its executives lavish six-figure salaries and retirement bonuses.

Ellis said it might not be glamorous, but Congress needs to be more proactive in its oversight role. "It's not going to get you a lot of TV time or make splashy news but it is a fundamental purpose of Congress, and a lot of times it gets thrown to the wayside. It's the eating vegetables side of legislating."

Fox News' Lucas Tomlinson and Jennifer Griffin contributed to this report.