Gregg Zoroya

USA TODAY Opinion

MONROVIA, Liberia — Ebola-infected blood arrives each day with a knock on the door.

Members of the U.S. military answer and take the samples. There's not a uniform or weapon in sight. The four sailors working in a laboratory at the end of a dirt road are deployed to fight a disease, not terrorists.

The vials they handle carry a name, gender and age — stark reminders, the sailors say, that what they learn can dictate if someone lives or dies.

Three of them are microbiologists, more accustomed to scientific research than fighting a deadly epidemic in West Africa. The fourth is a hospital corpsman. Their job since Oct. 2 has been to quickly identify patients free of Ebola, so they can be separated from those who have the disease; and to clear those who are recovering, so they can go home.

What they didn't anticipate was making an emotional connection with many of the hundreds of Liberians whose blood the sailors have tested. "I'm the person who enters every patient into the database. So every tube looks like a person to me whether it's a 5-year-old male that I'm entering or a 65-year-old female," says Navy Lt. Andrea McCoy, 42, the officer in charge.

The disease has killed more than 6,000 people in West Africa, according to the World Health Organization. While new infections in Liberia have fallen sharply in the last several weeks, the epidemic is raging in neighboring Sierra Leone and remains a threat in Guinea.

"We had one sample that came from a 9-year-old boy," says Navy Lt. Jose "Joey" Garcia. "That boy was one of the hottest samples that we had. And when I say hottest, I mean that it had the most virus within it. That in itself is a death sentence. "

The Navy testing lab here is one of seven in Liberia staffed by the U.S. Navy or Army. The troops are among 2,450 American servicemembers deployed to fight the disease. Just the addition of these new laboratories has rapidly reduced the time it takes to test samples.

Early in the epidemic it could take weeks to test for Ebola in drawn blood because labs were distant or few in number. Now results are available in a few hours.

"That right there is saving lives" says Garcia, 30, who back home works at the Naval Medical Research Center in Silver Spring, Md.

That the work might risk their own deaths has not been a major concern. Working from behind layers of protective gear, the sailor-scientists extract blood from each vial or body cells from each swab, and pummel them with ethanol and alkaline chemicals to kill the virus so it is safer to handle.

"There's always multiple layers of security between us and the actual blood samples," Garcia says. "I've never actually been afraid of working with the virus."

Standing at their door each day is a health worker or courier in gloves carrying a vaccine box. Inside are zip-lock baggies, each with a vial of blood drawn from someone being treated at the Ebola clinic next door or three other centers in the country.

In some cases, the boxes contain swabs taken from the mouths of people who have died. The sailors try to confirm whether Ebola killed them.

The samples are put in a centrifuge to isolate material containing the genetic code.

That material is then fed into two boxy computer analyzers — each taped with a nickname, "Rambo" and "Chuck Norris" — and the sailors wait for an answer.

It takes an hour. The machines read fluorescence emanating off treated samples. Results display as fever lines playing across a small screen. If a green line remains flat, the sample is negative for Ebola RNA. If it soars, the virus is present.

The sooner it soars, the heavier the viral load — and more lethal for the infected person.

The samples tell a story. The sailors can see when an entire family has been brought to a clinic and as the samples work their way through the lab, anxiety rises over whether a mother and father, and then young children, will all turn out to be infected.

"You're just praying that hopefully, the 4-year-old is negative," Garcia says. "It's quite emotional."

At times, where a sample is rife with the virus, the Americans reach the painful conclusion that this person will not be heard about again — conceivably yet another death from Ebola.

At other times they receive uplifting news — samples arrive bearing a familiar name, someone whose blood has been tested before and who is clearly in recovery. The sailors can track the patient's progress as the virus diminishes over time and the person is on the way to going home.

A high wall separates the laboratory from the Island Ebola Clinic next door. The gate to that clinic is just on other side of the wall from the laboratory. High on the wall is a guard outpost reached by a set of stairs from the laboratory side.

The release of cured patients has become a kind of ritual at the clinic. Those found free of Ebola wait to hear their names called and walk out.

The sailors who handled their blood can't resist climbing the stairs to watch.

"Everyone who is going to be released is lined up," says Navy Lt. Christina Farris, 31, a microbiologist. "They ... give them new clothes and a start-up kit and a certificate saying they are Ebola free."

Farris, who did her post-doctoral residency at Texas A&M Health Science Center, devoted her life to the study of microbiology and curing disease in the laboratory. But seeing real people emerge after beating back a terrible illness, the progress which she helped track in the Navy lab, was an altogether different experience, Farris says.

"Being able to participate in one of these humanitarian efforts like this and actually get to use my skills, that's pretty fantastic," she says.

So when the cured patients walk past, Farris says, she can't help cheering them on.

"We hear their names and it's exciting to see them. They're so happy to be getting out. They're praising God," she says. "It's wonderful."