[Been a little busy with Ebola in recent days. An American doctor has been evacuated from West Africa to Atlanta for treatment of Ebola virus disease — see our story from Saturday. The outbreak is the worst in history. We’ll stay on top of the story this week. In any case, I vaguely recalled that, a while back, I paid a visit to Fort Detrick, where scientists work on scary pathogens. My story ran Oct. 5, 1994 in the Style section. Here’s the link, but fyi it has an incorrect date. ]

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)

As you head up I-270 toward the Blue Ridge this time of year, you will see the first suggestions of autumn: the dogwoods skewing to orange, the sycamores sprinting toward brown and gold, the maples thinking about dropping the green in favor of red. The trees seek survival, unconscious that another species might find their tactics lovely. This is a good time for a walk in the woods, to reenter the natural world, to see and smell and hear its aesthetic delights.

But it’s also a good time to visit USAMRIID, the U.S. Army Medical Research Institute of Infectious Diseases. USAMRIID is at Fort Detrick, in Frederick, at the foot of the Blue Ridge. Here, nature is small, mindless and horrifying.

If USAMRIID were a store it would be called House O’ Microbes. It has a world-class inventory of bacteria and viruses. When the USAMRIID scientists and soldiers encounter nature, they do so in spacesuits in negative-pressure laboratories. If there were such a thing as the Andromeda Strain, this is where the Army would keep it. The Washington area has experts in almost everything imaginable; USAMRIID has experts in stuff we don’t even want to think about.

My strict policy when it comes to viruses is to avoid them like the plague, but viruses and bacteria are big news these days. There have been recent cover stories in the newsmagazines, there’s a pneumonic plague outbreak in India, there are Hollywood producers running around with contracts for microbe disaster movies.

Hollywood’s interest in viral epidemics was stirred by a New Yorker article by Richard Preston that has just been turned into a book, “The Hot Zone.” It’s the true story of a mysterious virus outbreak in 1989 in a monkey facility in Reston. By coincidence the Washington area had not only this lurking and potentially deadly virus (this town has everything, somewhere) but also this unusual Army facility with people capable of recognizing the virus and counterattacking in spacesuits.

The USAMRIID people feared the virus could be transmitted through the air into the human population, and that this would be bad — very bad, quite detestably bad — because the virus appeared to be an extremely lethal type called Ebola Zaire.

Preston’s book describes what happened to a guy who got a similar virus, called Marburg:

“… his whole head is turning black-and-blue. The muscles of his face droop. The connective tissue in his face is dissolving, and his face appears to hang from the underlying bone, as if the face is detaching itself from the skull. … By the time an extreme amplification peaks out, an eyedropper of the victim’s blood may contain a hundred million particles of virus. During this process, the body is partly transformed into virus particles. In other words, the host is possessed by a life form that is attempting to convert the host into itself.”

Then it gets even more disgusting. The guy basically turns into goop.

It’s a thrilling book, the reader frantically racing through the narrative to see if the virus is going to wipe out the Washington suburbs, crash into the White House, and force senators to evacuate the Capitol by helicopter, elbowing like mad, whopping each other with pork barrel bills as they scramble to grab the chopper’s landing gear. (You tell yourself that, had that happened in 1989, you probably would have heard about it, but this doesn’t make you read any more slowly. You also tell yourself to have some decency and stop rooting for the virus, for gosh sakes.)

So I went to USAMRIID, a beige building with, fortunately, not a lot of windows. Chuck Dasey and Cheryl Parrott, the USAMRIID spokesmen, were waiting in the lobby and it was nice to see that their faces were not hanging from the underlying bone.

Parrott led the way. At a double door she waved an ID card before some kind of sensing device and the doors unlocked. She went down a hall, waved the card again, went through more doors, then did it yet again at another set of doors, until finally we were in a corridor with walls of cinder block painted a color of green often found in junior high schools. We were just outside the biological containment areas.

I asked to go to a Biosafety Level 4 area.

“You don’t want to go there,” Parrott said.

Instead, we looked through a thick window into a BL-4 laboratory. There was what appeared to be an astronaut inside. It was a woman in a spacesuit. The suit was sky blue, with a pressurized rectangular hood. The woman wore mustard yellow boots and heavy gloves. Her suit was tethered to an air coil that disappeared into the ceiling. The astronaut was carefully placing something in test tubes.

“It used to be Crimean-Congo hemorrhagic fever in this lab,” Parrott said.

She signaled the astronaut to come to the window. “What are you working on?” Parrott mouthed.

The astronaut, barely audible through all the protective barriers between us, shouted, “Marburg.”

Ah! That one. Nasty.

The rest of the tour featured decontamination shower stalls and a “morgue” that Parrott said really ought to be called the necropsy room, since it’s for dissecting animals, not USAMRIID scientists.

At USAMRIID they have helpful color brochures explaining why the Army is collecting these dangerous bugs. The Army says this is science in the nation’s defense. Diseases can be weapons. One brochure notes: “Some of the earliest recorded uses of biological warfare are the Assyrians’ poisoning of an enemy’s wells with fungi and Solon’s use of the purgative herb hellebore during the siege of Krissa, both over 2,500 years ago.” (As Solon put it, “War is hellebore.”) There’s also a discussion of the Tartars’ siege of Kaffa in 1346. Some of the Tartar soldiers dropped dead of plague. Solution: Catapult the corpses over the Kaffan walls. The first biological warfare delivery system was born. The city surrendered. Fleeing citizens then spread the bacteria to other ports in the Mediterranean, and the Black Death spread through Europe, killing 23 million people in three years.

Things like that can give a bacterium a bad name.

Could we be eradicated someday by one of these nasty little bugs? As we clear out the rain forests, are we inviting long-hidden viruses to emerge, roam around the planet and convert our flesh into more virus? There’s an argument that says viral epidemics, such as HIV, are inevitable as the human species becomes an increasingly large fraction of the planet’s total biomass, of the planet’s meat.

Chuck Dasey of USAMRIID says the doomsday fears — a slate-wiper virus jumps out of the forest and kills everybody — are overblown. “It hasn’t ever happened. The world’s been here a long time.”

But it would make a great movie plot. Robert Redford and Jodie Foster were supposed to star in the “Hot Zone” movie. Ridley Scott, who made the movie “Alien,” was supposed to direct. Scott visited USAMRIID twice. His vision of the movie featured “exploding people,” Dasey says. Scott is certainly the expert on that after the explosion scene in “Alien.”

The movie fell through for a variety of reasons, including the fact that another studio was making a similar movie, called “Outbreak,” which didn’t pretend to be based on a true story and thus would have license to show people exploding all over the place, a real splatter-fest.

In any case, if there is a place perfectly cast for the cinematic revenge of nature, it is Washington, the seat of the empire, a monument to humanity’s love of power. From Washington we seek in ways both subtle and obvious to rule the world, or at least to correct it. Viral epidemics are a different kind of correction, one of nature’s brutal techniques for achieving balance.

We should remember that a virus is just a strand of genetic material, a thing so humble it is not really alive unless it is inside a host. And the plague bacillus is just a little one-celled creature that normally lives inside fleas and like every other form of life wants only to reproduce.

I’m not trying to start some Save the Plague sympathy movement here — if scientists want to experiment on plague bacteria it’s fine with me as long as they make sure the plague doesn’t experience any discomfort — but it is worth remembering that the plague means no harm. It probably aspires to be something noble, something benign, like penicillin. Its fantasy, surely, is to be multicellular. And maybe at night it dreams of being a sycamore.