© Isaac Kasmani/AFP/Getty Images
A member of the medical staff of the Ebola Treatment Unit at the Bwera General Hospital in western Uganda on Dec. 12, 2018.
Nearly 600 people have contracted Ebola since last August in eastern Democratic Republic of the Congo, making the ongoing outbreak the second largest in the 43-year history of humanity's battle with the deadly virus. And there is a genuine threat that this Congo health crisis-the 10th the African nation has faced-could become essentially permanent in the war-torn region bordering South Sudan, Uganda, Rwanda, and Burundi, making a terrible transition from being epidemic to endemic.

Despite having a tool kit at its disposal that is unrivaled-including a vaccine, new diagnostics, experimental treatments, and a strong body of knowledge regarding how to battle the hemorrhage-causing virus-the small army of international health responders and humanitarian workers in Congo is playing whack-a-mole against a microbe that keeps popping up unexpectedly and proving impossible to control. This is not because of any special attributes of the classic strain of Ebola-the same genetic strain that has been successfully tackled many times before-but because of humans and their behaviors in a quarter-century-old war zone.

The sheer duration of the present epidemic means that the 4.5 million people in the currently affected North Kivu province of Congo are no longer the only ones in danger. The rest of the country and populations in the bordering nations of Uganda, Rwanda, South Sudan, and Burundi are now at risk, too.

Like homicide detectives tracking murder clues, teams of Ebola hunters are scouring urban areas and remote villages across North Kivu province, trying to catch the culprit before it claims more victims. But all too often, this killer, which causes the deaths of 60 percent of those it infects, is leaving no useful clues. In past brushes with Ebola, humanity has won out by tediously, and often perilously, finding an infected individual and then tracking backward through the person's recent life to reckon who might have had contact with the ailing patient, building a chain of transmission that not only leads back to the first case introduced into a given location but also steers the disease detectives toward the killer's next likely targets. By building chains of transmission, the Ebola fighters know who to quarantine, where to target their searches for other patients, and how best to deploy limited supplies of vaccines and diagnostic equipment.

But day after day, cases are popping up all over North Kivu that don't connect to any known chains of transmission - it's as if they popped out of thin air. The problem: North Kivu is one of the most violent places on Earth, rife with distrust, rumors, conflicts, and multigenerational hatreds. Investigators can't find the links in the disease chains because the people there do not trust anything, even the very idea that a virus called Ebola exists, and refuse to comply with investigations.

On Jan. 11, for example, villagers in Marabo rose up in protest against the construction of an Ebola treatment center in their community after three high school students were diagnosed and placed in quarantine to stop a local chain of transmission. When international disease fighters tried to vaccinate all of the high school students, rumors spread that the vaccine was dangerous, students fled, and their three infected colleagues were helped to escape quarantine. Such events have been repeated throughout the area since the outbreak began.

An Ebola disease that became endemic in Congo would pose many novel dangers. The disease can be transmitted sexually up to 18 months after an individual's cure, and, like Zika and HIV, it can also pass from pregnant mothers to their fetuses. It can also spread within military units that refuse scrutiny from virus detectives and among groups involved in illegal war-related activities such as arms smuggling. Even immune survivors might be at risk in an endemic context, as a recent study found that Ebola survivors carry two types of immune responses-one that will protect them against future exposures to the virus and another that perversely enhances infection, worsening their odds of dying if re-exposed.

Peter Salama, who heads up the World Health Organization's Ebola effort, predicted in December that the epidemic would last at least another six months. And that's likely an overly optimistic forecast. "It's an outbreak I describe as a perfect storm - a combination of this deadly disease in one of the most difficult, protracted crises we have around the world," he told Vox last month.

The current crisis comes even though the disease has likely been slowed by vaccinations, which mostly weren't available during the last major Ebola outbreak in West Africa in 2014-2016. As of Jan. 11, teams have administered a Merck-made experimental vaccine to more than 58,300 people in North Kivu and small numbers of health care workers in neighboring countries, in case of cross-border spread. First used to halt a smaller 2018 outbreak hundreds of miles away in Congo's Equateur province last May, the vaccine is considered fully effective and has lowered risks to health care workers, 55 of whom (or 9 percent) have contracted the disease to date in North Kivu. In the West African 2014-2016 epidemic, in the absence of the Merck vaccine, health workers were up to 32 times more likely to contract Ebola compared with the populations they served, despite wearing protective suits.

"One thing I am really certain of now is: If it wasn't for the vaccine we're using, the number of cases we have could have been really high, high, high," WHO Director-General Tedros Adhanom Ghebreyesus said after spending New Year's Eve and two other days in the disease epicenter. It was Tedros's fourth trip into the heart of the epidemic. (No prior WHO leader ever set foot in an Ebola hot zone.) But despite swift mobilization by Congolese health officials, a strong WHO response, financing, the presence of humanitarian medical groups such as the Red Cross, Médecins Sans Frontières, and the Alliance for International Medical Action, an effective vaccine, and scores of volunteers and experts on the ground, the epidemic just keeps growing. "This is a very dangerous enemy, and we have to stay," Tedros said. "If we leave ... the virus will get an advantage and will spread freely. Not only for [Congo]-it will be bad for the neighboring countries and even beyond."

The epidemic has already transformed from what last summer was a remote, rural phenomenon to an urban mess in Beni (population 232,000) and Butembo (estimated to have around a million residents)-both bustling trade cities that are densely populated and located along a highway that parallels the Ugandan border and Semliki River. Farther south along the highway are two pivotal metropolises, Goma and Bukavu, each with a million residents, bordering Rwanda and Lake Kivu. Were Ebola to reach these cities, a top WHO official told me, "all bets are off," for stopping the epidemic.

Meanwhile, health responders keep playing that whack-a-mole game against the virus because the threat of violence from ongoing warfare in Congo limits their movements and public distrust impedes assistance with investigations. As a result, the disease keeps popping up in unforeseen places and people. Unlike in past outbreaks, UNICEF says more than one-third of the Ebola cases in this epidemic have been in children, the majority of identified adult infections have been in women, and nearly 70 percent of discovered cases have fallen outside of known chains of transmission. A significant unknown is the extent of Ebola in the ranks of warring soldiers, gangs, arms smugglers, and rapists. The groups have not only refused testing, but they have threatened health responders with guns and machetes.

This makes it even harder for public health officials to estimate future transmissions-a difficult task in any case, since past outbreaks have shown the disease can lie dormant for more than a year in tissue including the eyes and genitals. Raping and pillaging soldiers can carry the virus from village to village long after they may personally have survived the viral disease. Swedish Foreign Minister Margot Wallstrom, who served as the U.N. special representative on sexual violence in conflict from 2010 to 2012, dubbed Congo the "rape capital of the world" and said rape was simply a fact of life for women there. Going forward, that could make the current outbreak the first to be heavily transmitted, and reignited repeatedly, by sexual abuse.

Short of vaccination, the best tool for preventing endemic Ebola is the combination of contact tracing and quarantine-finding and blocking chains of transmission. But those methods require freedom of movement and public compliance, both of which are lacking in war-torn Congo. In a grim assessment last November, Robert Redfield, the director of the U.S. Centers for Disease Control and Prevention (CDC), told reporters that the outbreak might not be controllable and could easily become entrenched and endemic.

It's hard to know what steps could break the Ebola impasse. Warring forces have shown little inclination to give the disease hunters free rein across the region. Political leaders in Kinshasa are obsessed with the strongly contested results of the country's long-delayed national elections, leaving no clarity about who is in charge of the country at the moment. The United States has little skin in the game, as the Trump administration decided months ago that the security situation was too risky to allow any U.S. government employees-including CDC Ebola veterans-into North Kivu. U.N. peacekeepers are unlikely to either increase their force numbers or alter activities in any way that might make disease investigation safer, and the population views the United Nations with suspicion. Merck shows no sign of ramping up vaccine production to replenish or increase supplies. And on the front lines, the responders-the Africa CDC, WHO, a host of NGOs and humanitarian groups, and the Red Cross-are already toiling valiantly.

Comment: Unsurprisingly considering the UN's track record: UN finally becoming exposed as haven for rapists and pedophiles

Health officials in Uganda, South Sudan, and Rwanda see the writing on the wall: This epidemic won't end anytime soon and constantly threatens to cross their borders. They're preparing their health teams, giving them vaccinations and Ebola training. Vigilance is high across the region.

If Ebola hitchhikes its way in an unwitting human carrier across Lake Edward into Uganda, down the highway to Goma and Rwanda, or up the Semliki River toward South Sudan, the world community will face tough choices. Option one: Keep on muddling through with the tools, personnel, and funding that have carried the response to date. Option two: Declare a global public health emergency, escalating financing and on-the-ground response to the multibillion-dollar scale seen in West Africa. Option three: Dedicate massive financial resources to pushing Merck and other vaccine-makers to rapidly manufacture millions of doses, and deploy literal armies, acting as security alongside an enormous public health deployment to immunize tens of millions of people in the region.

Maybe we'll all get lucky, and the virus will just peter out. But there's no reason to think it will.
Laurie Garrett is a former senior fellow for global health at the Council on Foreign Relations and a Pulitzer Prize winning science writer. @laurie_garrett