The Four Horsemen of the Apocalypse — Pestilence, War, Famine and Death — gallop through the Book of Revelation, and they’ve put in plenty of grim appearances elsewhere. Lately they’ve stabled their mounts in North Korea, where, having starved millions, a grisly dynasty preaches war, while developing not only nukes but diseases as weapons.

North Korea isn’t a country, it’s a death cult.

A recent defector from Kim Jong-un’s nightmare regime had anthrax antibodies in his system. It’s further evidence that, along with nuclear-weapons development and the use of chemical weapons (even on family members), Pyongyang’s less-discussed biological-weapons program — epidemic diseases as weapons of war — continues to sharpen its scythe.

The anthrax resistance in that North Korean’s system came either because he was inoculated as an elite guard near a research facility, or because he’d been exposed to anthrax and built up resistance. Neither possibility is good news.

“Germ warfare,” the use of pathogens to break an enemy’s resistance, is taboo in the modern age, but it has a hoary history.

From warfare’s earliest days, armies left behind diseased corpses to infect opponents. In siege warfare, plague victims were catapulted over city walls to deplete defenders. As smallpox-ravaged redcoats retreated toward Yorktown at the climax of the American Revolution, Lord Cornwallis had his soldiers drop infected blankets, clothing and gear by the roadside, hoping smallpox would grip the “colonials,” too (Washington ordered his men to touch nothing and had all items burned).

In World War II, the Japanese tested plague on Chinese civilians. Later, the Soviet Union pursued the weaponization of lethal pathogens — and not without gruesome accidents. Moscow’s research facility in the Aral Sea was considered one of our planet’s most fearsome places.

When the Soviet Union collapsed, researchers looked for new homes. Some, undoubtedly, turned up in North Korea.

There are two key problems with bio-weapons. On the technical side, a pathogen must survive delivery in a bomb. In the case of a missile warhead facing heat and stress upon re-entry into the atmosphere, a very hardy bacteria or virus is required.

That’s why anthrax is often the weapon of choice. While it’s not as lethal or as terrifyingly graphic in its effects as smallpox or plague, the anthrax bacteria is tough. Scientists in programs such as North Korea’s strive to make it even more durable and deadly.

At a time when activists here and in Europe shrilly protest genetically modified food, they’d be wiser to worry about genetically modified diseases (North Korea’s research surely is not limited to anthrax).

Which brings us to the obvious problem: Once unleashed, pathogens don’t follow orders. It’s extremely doubtful North Korea could inoculate all of its military, let alone its entire population — it’s just too poor (and callous). An epidemic sparked in South Korea could easily backfire, given North Korea’s primitive health care.

Of course, the even greater danger from disease modifications that render known vaccines and treatments ineffective is that an attack might not stay local or regional but spark a pandemic. With anthrax, that’s less of a threat than with, say, juiced-up pneumonic plague or amped-up influenza (the greatest killer of the 20th century), but we just don’t know what might emerge from Madame Pandora’s box.

And even a failed biological attack swiftly contained could serve a tyrant’s purpose — germ warfare’s the ultimate terror weapon: Humans are programmed to dread disease. Heroes may rush forward to disarm a gunman, but nobody dashes toward a fellow human bursting with pustules and puking blood in the street. Our programmed reaction is panic.

All this is further complicated by the welcome fact that we’ve overcome so many killer diseases. We’re accustomed to a level of safety from epidemics unthinkable to those who came before us. We blithely assume that public-health authorities can handle any problem.

The truth is that we’re profoundly unready, psychologically and practically, to deal with an epidemic on the scale of the Spanish flu of a century ago. Our health-care system would break down and our centralized food supply would crumble. Vainly attempting to enforce quarantines, the National Guard would be hard put to handle the corpses — and all first responders would suffer a heavy death toll.

We can deal with North Korea’s nukes, one way or another, but we need to take biological weapons — there and elsewhere — far more seriously than we do. Kim Jong-un’s riding with all Four Horsemen of the Apocalypse, not just the one glowing with radioactivity.

Ralph Peters is Fox News’ strategic analyst.