I'll add my 2¢
Stories begin on a status quo.
Your story is set in a post-apocalypse – maybe a current-apocalypse – so your status quo at the start of the story is precarious.
I'll make a few assumptions:
- The pandemic has already started.
- The village has policies to keep the virus from spreading (which fail obviously).
- The origin of how/where the virus started is unimportant at this point in the story (if ever).
Why you don't want a Prolog
Prologs are 100% factual because they are foundational knowledge that comes directly from the only true authority: the Author.
Your genre/setting is about the breakdown of society, the loss of law and order, and the end of anything reliable. The 'facts' that you clarify in your prolog work against your genre and setting.
Early in the COVID pandemic, the origin of the virus was learned to be a random (but normal) mutation of an animal-virus spread through a food market. There is no literary payoff from this piece of trivia. IF there was any moral lesson to be learned it was something about the Earth's shrinking wildlife habitats and the inevitable march towards globalization – bla bla....
There's nothing special about this origin story, it is the same origin of almost every viral disease, hence swine flu, chicken pox..., HIV originated in apes. Viruses mutate every day. The fact that people politicized it, and conspiracy-alized it, is far more interesting (story-wise) than the truth.
A factual prolog would render all that drama moot. It's like telling the reader whodunnit and then asking them to enjoy the detective solving the mystery when they already know the red herrings.
House of cards
The precarious status quo of your village is going to fall apart like a house of cards.
People do disastrously stupid things when they panic. They reach for quack cures and superstition, they reject sane authority and experience, they single-out the usual suspects to scapegoat, and they horde toilet paper.
You will have characters that do ALL these things, but as the author you don't want to tip your hand which characters are right/wrong because everyone is going to panic and change their routine. In a dystopia everyone does the wrong thing – people are unfairly punished for doing the right thing – and there are no clear answers because everything is morally grey and about survival.
I agree with Phil S' suggestion to sketch-in the 1st chapter, and re-write it once you know your major plot points.
Stranger in a strange land
Start with your outsider protagonist entering the village and encountering world building: arbitrary rules that subjugate the already marginalized, quack cures and street preachers, and $1000 rolls of toilet paper.
Go back and add some of those 'plot hooks': those shaky pillars on which the village is currently standing which will spectacularly collapse later: unjust authoritarianism, a faulty belief about the virus, pressure from the local industries to trade-as-usual, and unhelpful counter-narratives from the fringes.
All these things will help the village appear foreign and hostile. Readers should feel apprehension about the village, and familiarity with the protagonist who is our witness. Ironic because she is bringing the danger to them.
If the rules feel arbitrary and draconian, readers will empathize with her lying to get in. We don't need to know her backstory yet, or why she's lying. We especially should not know she's bringing disaster. Focus on her immediate antagonists (unsympathetic guards? an invasive medical check? security theater?), and the conflict of how she's going to guile her way inside.
Leave room for disaster
It may be necessary to imply her need to be inside the village (or her need to not be outside the village) to add a ticking clock to her fc conflict. But naturally, this is not what she says at the gate so there's no need to frontload her bigger conflict that isn't in evidence yet.
As hostile as this strange land appears now, everything will get worse over the course of the story, so keep the opening conflict immediate and personal to her. Show her as sympathetic underdog, so the reader is on board with her immediate goal.
Introduce other important (to her) characters and local conflicts that will complicate her story –– but just introductions. She does not know their significance so she will make selfish decisions which she may regret later. Example: She guiles her way past a guard with a sob story, someone she will need later who won't trust her because of this earlier lie.
Since she is essentially a different character in the first conflict than the one we'll get to know, readers will give her the benefit of assuming her underdog status justifies her behavior. We should celebrate her earned 'win' and accept her as the story's hero.
Discovering later that she has serious moral flaws, and is culpable for the deaths she brings, aligns with the genre. Readers experience a rug pull, or a slow-burn negative arc, as other characters experience their reliable world falling apart and friends betraying them.