When the clock strikes noon Friday, presidential inauguration day, there will be another transition of power some 600 miles southwest of the White House. Tom Frieden, director of the U.S. Centers for Disease Control and Prevention, will hand over his Atlanta-based agency to an acting director, a career civil servant named Anne Schuchat who has been serving as Frieden’s principal deputy director. Succession for this temporary role is spelled out by a federal law that applies to top government vacancies.

On day one of the Donald Trump administration, Schuchat will already be grappling with numerous threats as the agency continues its work of investigating outbreaks and seeking to prevent new ones. In the past seven and a half years under Frieden’s leadership the CDC has been roiled by crises including government furloughs, H1N1 flu, lab safety issues and the U.S. responses to Ebola and the Haiti earthquake. The agency is also still in emergency mode as it confronts the mosquito-borne Zika virus and its related birth defects. And the hits are likely to keep on coming.

The CDC will struggle to deal with emerging threats because it does not have the cash or power to respond immediately in a crisis, Frieden says. “There’s a need to establish a rapid-response fund for emergencies that has both dollars and emergency authority,” he told Scientific American. “It’s a big problem that when there is an emerging threat, we are not able to surge as rapidly or work as rapidly as we should, because of lack of money and legislative authority. When there is an earthquake, FEMA doesn’t have to go to Congress and say, ‘Will you give us money for this?’ but CDC does.”

The agency has other money troubles, too. Its Prevention and Public Health Fund, which is part of the Affordable Care Act, accounts for more than a tenth of the agency’s budget, Frieden notes. Its monies support immunization programs to prevent disease and block grants to states, he says, adding that a repeal of the ACA—a stated priority of the Trump administration and the congressional majority—would endanger these programs. “Zika is the first predictable problem,” Frieden explains. “Zika is not over. It is likely to spread in Latin America and the Caribbean for months and years to come, and we still don’t fully understand the range of birth defects it causes.” Other big issues include combating antibiotic resistance in the U.S., stemming the opioid epidemic that has quadrupled overdose deaths in the U.S. since 1999 and remaining vigilant against the perennial onslaught of influenza—as well as emerging threats including tick-borne pathogens.

Schuchat is a “steady hand,” says Frieden, who has submitted his resignation per presidential transition protocol. Schuchat has been at the agency for almost 30 years, but exactly how long she will be in the top spot remains unclear. The CDC chief, unlike those at the Department of Health and Human Services or the Food and Drug Administration, does not require Senate confirmation, so an appointment choice will not snag on confirmation hearings. For now, Schuchat says, “It is a privilege to have the opportunity to serve our nation’s premier public health agency and CDC’s critical mission of saving lives and protecting people from health threats.”

Keeping an acting head in the top spot for an extended period may breed problems, however. “You always want to have someone who can have a strategic vision and a strategic plan,” says Ezekiel Emanuel, chair of Medical Ethics and Health Policy at the University of Pennsylvania. Someone in a temporary role “can’t develop strategic plans—it just doesn’t happen,” he says.

The most crucial quality for the next CDC director will be public health training—especially when it comes to understanding data and communicating with the public—says Lance Price, a microbiologist and director of the Antibiotic Resistance Action Center at The George Washington University. “I really worry about leadership who will dismiss science when it is politically expedient. The person doesn’t necessarily have to be a clinical physician but I think public health training and training in epidemiology, statistics and risk communication are all really important qualities,” he says. “Scientists speak in our code all the time and that doesn’t work for the general public. You have to have a good grounding in science and public health so you can understand what your key team members are communicating to you, and then you have to translate that to the general public.”

The person in this position will also need strong skills in international diplomacy, Price cautions. “No [country] wants to report that they have super-resistant infections…because they are worried about people not wanting to travel to their countries,” he says. “I’m concerned that if [that person] is not diplomatic about this, we could lose control very quickly. We need trust-building.” The recent death of a Nevada woman who visited India and contracted a superbug infection—which resisted all available antibiotic drugs in the U.S.—only underscores that risk, he says.

The new CDC head will have to be able to navigate bureaucracy and politics, says Mark Keim, a former official who in his 16 years at the CDC helped the agency grapple with science amid emergencies including the anthrax scares that followed the terror attacks of September 11, 2001. “The political mind-set of this administration may be a bit more inclined to limit the number of resources to CDC unless it’s an emergency, so these ideas of getting out ahead of these problems into delicate or sensitive social issues—like the association between poverty and disaster death—those won’t be well addressed during the next administration to prevent disaster deaths,” he says.

Any CDC director, as the face of public health, will also have to be a capable advocate for global health–funding investments. Staving off disasters around the world is the only way to protect the U.S., says Amy Pope, deputy homeland security adviser to Pres. Barack Obama. “Pandemics don’t know borders. This is not something we can solve by shoring up our borders,” she said at a public event earlier this month at Georgetown University Medical Center. “The best way to protect our homeland is to make investments around the world,” because we only know about threats if our partners around the world have the capacity to detect, respond to and control threats, she said, adding that when it comes to pandemics, plans and prior infrastructure must be in place because “we don’t have a lot of time for bureaucracy.”

Frieden, who is the second-longest serving CDC director in the agency’s history, says his years at the helm were marked with successes that include affirming the link between Zika virus and microcephaly, helping beat back Ebola and supporting programs that promoted a drop in U.S. teen pregnancy numbers. “By reducing teen pregnancy, we have been able to reduce poverty,” he says.

Frieden has not yet decided what he will do next. “I have always made my career decisions by asking one simple question: ‘How can I save the most lives?” he says. “And that’s the question I’ll ask going forward.”