Joseph Fair, an American virologist, is working as a consultant at the World Health Organization headquarters in Sierra Leone. (Michael Duff/For The Washington Post)

Joseph Fair hunts viruses. That’s his thing. The 37-year-old American loves chasing dangerous pathogens, studying them in secure labs or searching for them in jungles where the microbes lurk.

And one virus has always loomed as the big one — Ebola. The scientists who first chased this dreaded microbe back in the ’80s and ’90s became legends, inspiring a generation of virologists like Fair. He read their books and papers. He studied how they contained the pathogen’s spread. And the scientists always won. The outbreaks ended, Ebola driven away.

So when the call came in March to travel to Sierra Leone, Fair was excited. He loved Mama Salone, as locals know the nation. He’d worked here for years. His new job: to advise Sierra Leone’s government on a tiny Ebola outbreak in neighboring Guinea, at the behest of the U.S. Defense Department. He set up an Ebola emergency operations center. He trained medical staff. He drew up just-in-case plans. By mid-May, the outbreak seemed on its way out. Fair packed his bags and left.

Then Ebola exploded.

Now, Fair is back in West Africa, in the middle of the worst Ebola outbreak in history. A viral epidemic. The world’s ability to respond is stretched. Plans are being devised on the fly.

As the worst Ebola outbreak in history unfolds in West Africa, The Post's Joel Achenbach explains how the deadly virus wreaks havoc on the human body. (Davin Coburn/The Washington Post)

“This is the big one no one expected,” Fair says.

It has been a humbling time. Fair has worked seven days a week, hunting for ways to curb the outbreak, at times begging international groups for staff and supplies. He is exhausted. He’s put on 15 pounds. He sent his girlfriend home to California months ago. Too dangerous here, he told her. He’s seen Sierra Leonean doctors and nurses — friends he’s known for years — get infected and die. He sweated out his own Ebola scare.

“It’s like he was trying single-handedly to stop this outbreak,” says Randal Schoepp, chief of the U.S. Army’s applied diagnostics branch at Fort Detrick, Md., who has worked with Fair in West Africa.

But the number of new Ebola cases has just kept shooting higher, like an unbreakable fever.

For Fair and other scientists, this has not felt like failure. It is more complicated than that.

“As bad as it has been,” observes Connie Schmaljohn, senior research scientist at the Army’s Medical Research Institute of Infectious Diseases, “it could’ve been worse if people like Joseph hadn’t been there.”

Under pressure

Now, Fair is taking a rare break. He is sitting on the outdoor deck at a hotel where U.N. peacekeepers used to live after this country’s long civil war. The Mammy Yoko today is filled with aid workers and doctors. Fair wears a black T-shirt and blue jeans, his blonde hair going gray near the temples. He is nursing a double shot of whiskey, a nod to both his eastern Kentucky roots and his mounting stress.

The son of a nurse and a college professor, Fair grew up with dreams of being a missionary. He wanted to help people. In college at Loyola University New Orleans, he read “Virus Hunter,” about famed virologist C.J. Peters’s career chasing Ebola and other pathogens. Fair discovered a new calling. A few years later, he was working at Peters’s lab at the University of Texas Medical Branch in Galveston. Peters recalls how Fair volunteered to work with hot viruses in the highest-security labs.

“That indicated right away that he was going to do things,” Peters recalls. “It’s been gratifying to see him take up the cudgel.”

Now, on the hotel deck, another famed Ebola hunter sits at a nearby table. Tom Ksiazek was recently tapped by the Centers for Disease Control and Prevention to help in Sierra Leone. He and Fair work together at the Ebola emergency operations center.

“A CDC legend,” Fair says with admiration after Ksiazek stops by to say hello.

In a far corner, a group gathers to welcome the new World Health Organization representative in Sierra Leone. The previous one had been shipped home. The WHO blames exhaustion. But many here see it differently.

“Someone has to take the fall when things go like this,” Fair says.

“Like this” would be the criticism that the WHO and other international groups were slow to respond to the tragedy in West Africa. Governments are under pressure, too. Liberia’s government could fall. Sierra Leone’s health minister, who was officially directing the national Ebola response, lost her job last month.

But no one expected this epidemic. No one anticipated that Ebola — a disease with no cure and a 21-day incubation period that is spread through close contact with blood, saliva or sweat — would sweep into urban areas, especially in West Africa. Every previous outbreak occurred in remote settings.

“You’d like to think someone was thinking about this all along,” Fair says. “But not so much.”

In 2012, Fair gave a talk that seemed to foreshadow the current crisis. He was working for a company that aimed to head off pandemics, such as the H1N1 flu and SARS. At San Francisco-based Metabiota, formerly called Global Viral Forecasting, founded by well-known virus hunter Nathan Wolfe, Fair conducted lots of medical diplomacy work for the U.S. government.

In that talk at the World Vaccine Congress, Fair warned about delays in tackling viral outbreaks. “We truly have a political problem when it comes to responding to these diseases,” he said.

So it seemed like a good sign when Fair was dispatched to Sierra Leone in late March before even the first Ebola diagnosis was made. The WHO had asked for his help. The Defense Department sent him — more medical diplomacy. Guinea was investigating 49 cases of an unknown hemorrhagic fever.

Fair knew Sierra Leone from his work at a U.S.-funded lab that focused on Lassa fever, a hemorrhagic fever similar to Ebola, but spread by rats. The small lab in the eastern city of Kenema was the county’s most advanced, the only one capable of testing for Ebola.

Before he could get settled, Guinea’s mystery illness was confirmed as the dreaded Ebola.

Fair and others raced to face an Ebola outbreak expected to spill across borders. Hospital staff were taught to look for the high fevers and weakness of suspected Ebola sufferers. Isolation wards were set up. Medical surveillance teams were trained to track infections. Rubber boots, bleach and thermometers were distributed. A national media campaign was launched to introduce 6 million people to a disease never seen before in Sierra Leone.

“There were a lot of people in denial that it was real,” Fair says.

And he waited. April turned to May. Hundreds of people with Ebola symptoms were tested: Nothing. Not a single case. Guinea and Liberia were quiet, too. Aid groups such as Doctors Without Borders were optimistic. The WHO declared the outbreak, after about 260 cases, “stable.”

Scientists consider an Ebola outbreak extinguished if no new cases are detected after 42 days — the length of two incubation periods. That vital deadline approached in the last week of May.

Fair flew to Paris. He was burned out. He’d been hustling for weeks. He’d broken with Metabiota and was heading out on his own. Then, on May 25, he received an e-mail from the WHO: Ebola was back.

‘Everyone freaked out’

New cases were reported in Guinea and Liberia, plus Sierra Leone. Fair was stunned. They had been so close. He wanted to return to Mama Salone. A couple of weeks later, the Defense Department asked him to go back. They couldn’t pay him, but they could cobble together enough funding to cover his flights, a small per diem and his health insurance.

He returned in early July. He set out to Kenema, a four-hour drive from Freetown, to visit his close friend Sheik Humarr Khan, a virologist who ran the Lassa lab and was now caring for Ebola patients. Fair delivered fresh supplies of biohazard suits and gloves. He hugged and kissed the hospital’s head nurse, Mbalu Sankoh.

Days later, Sankoh developed a fever. It was Ebola. Fair had been exposed. He spent three weeks wondering if he felt hot, wondering if every ache was a sign of a raging infection.

He was lucky. But Khan contracted Ebola. Forty hospital staff in Kenema ended up being infected. The Ebola ward was overwhelmed. When Khan died July 29, the nation was stunned. He was hailed as a national hero. But people’s confidence was rattled. And the preparations for handling the Ebola outbreak, already teetering, collapsed.

“That all went to pot because everyone freaked out,” Fair says.

Hospitals shut down. Nurses refused to work. People became afraid to admit they were showing signs of Ebola, leading to more infections. Fair felt the world was ignoring the seriousness of the outbreak. He pleaded for more biohazard suits, rubber gloves, cellphone cards for staff trying to trace Ebola contacts, fuel for cars used by Ebola surveillance teams. He’d request field epidemiologists to track the outbreak in far-flung provinces. He got data epidemiologists to sit in offices. He spent days on the phone trying just to source ambulances equipped with dividers between the front and back.

“We were pretty much isolated teams functioning on the basics,” Fair says.

The number of Ebola cases has surpassed 4,000. Some think it could reach 20,000 or much higher. Now, just stopping new infections, gaining some control of the pathogen’s spread, is the goal. That will take months. The world is paying attention now.

Starting Friday, the country will shut down for three days. Almost no one will be allowed to go outside. The forced quarantine is like digging a break line to slow a raging fire. It might buy a little time. It will allow 20,000 workers to hunt for overlooked Ebola infections and conduct rapid malaria tests to rule out that common disease. The workers also will try to educate people about Ebola and hand out 1.5 million bars of soap.

It’s never been tried before. Fair is unsure whether it’ll work. This is a poor country. Many people don’t have refrigerators or ample supplies of food at home. Officials will probably have to transform empty schools and churches into makeshift Ebola isolation wards just to handle the crush of newly uncovered cases. But Fair believes it’s important to reinforce messages about how Ebola is spread and how it can be stopped.

The world has never seen an Ebola outbreak like this. The famed virus hunters of the past never dealt with a hemorrhagic fever entrenched in cities. In two weeks, Fair will fly to Washington for a congressional panel discussion on Ebola, joining CDC Director Tom Frieden. Fair wants to draw more attention to what’s happening in Sierra Leone. He could also use the break. Exhaustion is creeping back in. But he’ll be going back to Mama Salone. He is not giving up.

“If the world lets me,” he says, “I won’t let this ever happen again.”