With its sequel, “Peninsula,” in the can and slated for release whenever the REAL viral invasion lets up (Fall?), I guess I’d best catch up on “Train to Busan,” the movie that inspired it.

“Train to Busan” (2016) didn’t reinvent the zombie genre or best “World War Z” and make anybody forget that zombies have been utterly beaten to death (tee-hee) by the Sons and Daughters of George A. Romero when it came out.

But it bested most zombie stories in its humor, pathos and novel setting. An outbreak explodes out of a lab in the Exotic East. A KTX bullet train departs for points South just as the TV news catches up to a calamity exploding across the “peninsula.” And on board, a collection of character archetypes.

Who gets to live, who will perish and how many of the Walking, Stumbling, Jerky Dead will they take down with them when they do?

Two things stand out, catching up to this 2016 release in the middle of a real-not-sci/fi pandemic. One is the general simplicity of Sang-ho Yeon’s film. Zombies can be created with effects or performances, and this one leans heavily on actors mastering that angular, herky-jerky, head-snapped-back lurch, the blank-eyed foaming at the blood-spattered mouth fury. Couple that to pixelated movement — deleting frames to accentuate the jerkiness (an “in camera effect,” in essence) and you’ve got convincing menace, peril that comes from a recognizably “human” monster.

Nothing digital about it. The waves of people, the flood of zombie-lemmings tumbling out of a train station window, are real. None of this animated “World War Z” ants piling up in front of Israeli walls.

And the second stand-out trait, seeing this in the middle of an epidemic that Korea responded to and the Trump Sycophancy did not, is the pathos. Many a movie in the genre has focused on parents and doomed children, or vice versa. The more recent turn towards “zombies have feelings too” — an unfortunate outgrowth of films like “Warm Bodies” and the endless “Zombies Went Down to Georgia” TV series — is ignored.

“Train to Busan” has a distracted, workaholic divorced dad (Yoo Gong) forced to pay closer attention to his “I want my mommy” daughter (Su-an Kim).

There’s the bickering teen couple (Sohee and Woo-sik Choi) traveling with their high school baseball team.

The very-pregnant wife (Yu-mi Jung) who bitches about her “idiot” muscle-head husband (Dong-seok Ma).

We see doting, elderly sisters, efficient and courteous conductors, stewards and stewardesses, and that one “Save my own skin, SCREW you all” fat cat conservative (Eui-sung Kim).

They’ve all missed the hints, the warnings. Maybe they caught the first news reports. Little Soo-an saw crowds gathering around some incident at the train station as they were departing.

Mr. Suh (Gong) got alerts from his office about a “strike” at a facility his firm is invested in.

“I’ll be back before lunch,” he says (in Korean with English subtitles).

And nobody saw the staggering, bloodied coed who slipped onto the train, her veins blackening, her eyes not-quite the pale while of the infected.

But within minutes of leaving the station, the rail car’s TV screens start to tip them off. Their phones ring. The conductors make “please return to your seats” and “we WON’T be stopping” at the next city announcements.

All hell breaks loose, and it’s a brawl — car by car, row by row — with passengers stunned into shock, then forced into action. There’s improvising, do-it-yourself tactics, name-calling and figuring out who you can trust in a pinch.

The “idiot” husband makes up a nickname for Mr. Suh, who almost locks him and his pregnant wife out of the “safe” compartment —“Hangmum.”

But the father and the father-to-be need each other if they’re going to protect the little girl and the pregnant wife. Who cares if “Hangmum!” is how the guy tells at you, calls to you and begs for your help?

There’s a cynicism about government that plays as doubly ironic now — officials in yellow emergency service jackets asking citizens to “Please refrain from reacting to baseless rumors…To the best of our knowledge, you safety is NOT in jeopardy. TRUST the government.”

A government whose competence you can trust is what spared South Korea what Italy, Spain and the United States are enduring.

The set-pieces here are better than average for the genre — a tidal wave of troops in camo turned zombies overrunning a train station, a furious “Old Boy” charge through zombie-infested passenger cars.

As I say, “Busan” doesn’t reinvent the zombie movie so much as make it work well enough that you buy in — good performances, a nice selection of moments of “sacrifice,” the usual “What are they THINKING?” twists.

But I was surprised at how touching a couple of moments were, delighted by how badass some of the action beats played out, the suspense of some moments and vicarious fury of others.

There’s not much room within the genre for invention and novelty, something that works against “Busan” and hangs over “Peninsula,” pre-release.

The “rules” vary from picture to picture, but one new “what separates us from them” pays off, and we can only hope “Peninsula” remembers it.

Zombies don’t sing.

MPAA Rating: unrated, gory, graphic violence, profanity

Cast: Yoo Gong, Yu-mi Jung, Dong-seok Ma, Su-an Kim , Eui-sung Kim

Credits: Directed by Sang-ho Yeon, script by Joo-Suk Park, Sang-ho Yeon A Well Go release on Tubi, Amazon Prime, elsewhere

Running time: 1:57