Time for a thought experiment! (For those of us who don't want to keep chewing on the sore that is the US presidential succession—if you do, please stick to this already-existing discussion: cross-contamination into this new discussion will be dealt with harshly.)
We all know by now that Elon Musk wants to appoint himself Pope-Emperor of Mars. As the world's richest man (currently, and only on paper—it's based on the Tesla share valuation, which is wildly inflated) and as the guy with the private space program that scooped 50% of the planetary civil launch market in the past decade, it's not entirely inconceivable. Evidently SpaceX hope to fly Starship to orbit in the next 1-2 years and land a Starship on Mars within this decade. Let's suppose it happens.
So then ...
Let's suppose that Musk's Mars colony plan is as viable as his other businesses: there are ups and downs and lots of ducking and weaving but he actually gets there in the end. All the "... and then a miracle happens ..." bits in the plan (don't mention closed-circuit life support! Don't mention legal frameworks!) actually come together, and by 2060 there is a human colony on Mars. Not just an Antarctic-style research base, but an actual city with a population on the order of 500,000 people, plus outlying mining, resource extraction, fuel synthesis, and photovoltaic power farms (not to mention indoor intensive agriculture to grow food).
Most of the city is tunnelled underground, using the rock overhead as radiation shielding. The radiation level to which citizens are exposed is nevertheless higher than in any comparable city on Earth: it's just the way Mars is. Workers in the outlying installations may be much closer to the surface than city-dwellers, and indeed most such plants are staffed on strict rotation by workers who are exposed to near-surface radiation levels for no more than three months in any consecutive Martian year.
Obvious aspects: cities are easier to heat and protect against radiation and provide with air and water, so housing is dense—think Singapore or Hong Kong density. High energy activities (eg. fuel and chemical synthesis, metal refining) and work with toxic substances are carried out sufficiently distant from the dense habitat that there's no risk of explosion damage. Musk's tunnel boring fetish turns out to be pretty useful when it comes to building a narrow-gauge mass transit system to move workers to/from these outlying sites, so there's a subway linking the city to most of its far-flung human-operated work sites.
More remote work is either fully automated, or largely automated but overseen by a small local dome full of canned apes with space suits. (Think the folks who go out to fix wiring faults on the big-ass solar farms, or to repair the robots that clean the PV panels after the dust storms pass).
The city is large enough that "self sufficient" is within sight. There's a teaching hospital and a university (a lot of educational material is distance-learning based but it's a hub that provides for tutorials/symposia and lab space). There's a semiconductor fab line, although the mine and refinery for on-planet sources of rare earth dopants keeps getting shoved back into the future: easier to import a few tons of gallium and lanthanum and so on from Earth every couple of years at a few million dollars a ton rather than spend 10% of your planet's GDP on a refinery that'll only break even after several decades. It's still a net population sink (most terrestrial cities were, until the industrial revolution: more people died than were born there) but there is a birth rate and it turns out that with a sufficiently good medical system babies can be born and raised on Mars without too many medical issues.
The population is overall young: nobody has lived there for more than 40 years so far, the oldest citizens are around 80 years old but somewhat more mobile than on Earth (having been born on Earth and now living in a lower gravity environment), and chronic illnesses that prove fatal on Earth over a period of years (eg. Alzheimer's) are either curable by this point, or result in short incapacitation followed by death. (In 2120 there will be a huge scandal and public commission of enquiry into the policy of "assisted dying" applied by the authorities to most of the first generation of colonists who lived significantly past their productive years, but that's another scenario. Let's just say, retirement of 12-18 months is tolerated: retirement over 24 months is almost unheard of because retirees are widely believed to "just give up".)
Most of the necessities of life can be manufactured or recycled with only minimal inputs. Pharmaceuticals, for example: modular chemical synthesis "bricks" can be plumbed together to produce different drugs flexibly. Lots of research aimed at disaster resilience on Earth—portable modular pharmaceutical factories, basically—turns out to be applicable on Mars. And mandatory pre-vaccination of colonists keeps the major human plagues from ever gaining a toe-hold in the new colony: there is and will be no mumps, flu, common cold, polio, smallpox, COVID19, HIV, or rabies.
The habitats are of course instrumented and surveilled exhaustively. Nobody wants to accidentally wander into a room that is anoxic because an air circulation fan packed in, or to sleep in a near-surface dormitory where a heater failed at night in winter. Nobody wants to asphyxiate in a cloud of sewer gas that burped from a waste tank with a blocked extractor pipe. Nobody wants to starve in a famine because the strain of fungi which play a vital role in some obscure phytonutrient recycling pathway got infected and crashed. And so on.
(Politics: Musk's autocratic dream didn't outlast his own lifetime and Mars is very locked down—ridiculously so, in the eyes of anyone accustomed to life on a planet with a self-sustaining biosphere. It turns out that dog-eat-dog capitalism is a bad fit for domed cities, which can't tolerate homelessness, civil unrest, or unmedicated schizophrenia. So socially it's a lot more like the Soviet bloc than the early 21st century EU or USA, albeit with much better planning/control/management and a governing ideology which boils down to lifeboat utilitarianism—"we're not building utopia, we're just trying to ensure survival for as many as possible in an intensely hostile environment (what were our grandparents thinking?)".)
So I'm going with the most optimistic take on a Mars colony in 2070 (short of invoking magical singularity woo and benevolent superintelligent AIs running everything).
What happens next ...
One of the regular biannual colony shuttles from Earth brings an unwelcome surprise: some of the essential supplies for the life support farms are contaminated with SARS-CoV-70, leading to an outbreak which starts among workers in one of the agricultural units (possibly a potato farm—h/t to "The Martian" here).
SARS-CoV-70 is the latest emergent vaccine-resistant mutant from the clade of respiratory coronaviruses descended from SARS-CoV-19. Failure to vaccinate to achieve global herd immunity in the 2020s resulted in these coronavirii becoming endemic, and with a large host population (natural immunity seldom lasts more than 1-2 years: often only months) it keeps throwing out mutant strains (eg. Lineae B.1.1.7, the more infectious strain of the original disease, which emerged in late 2020). When a new strain of SARS emerges which is resistant to existing vaccines, the World Health Organization coordinates another global emergency vaccine response, usually releasing a tweaked mRNA vaccine within 90 days: often only local lockdowns are necessary while the first doses are airlifted to the outbreak site. On Earth, SARS-type diseases are a recurring but well-understood problem: new outbreaks compare to the COVID19 pandemic of 2020-2024 much as a winter flu pandemic in the late 20th century compared to the 1918-22 Spanish Flu.
Mars is different.
Firstly, SARS-CoV-70 is vaccine-resistant: the Mars colony is a green field zone. Indeed, the policy of excluding diseases prior to emigration has resulted in a younger generation (20-30% of colonists) who are unvaccinated against anything, and probably didn't learn about historic plagues in history class (because why would they?).
Secondly, SARS-CoV-70 is comparable in mortality/morbidity and infectivity to the original COVID19: the one twist is that "long covid" post-viral damage is more prevalent, affecting up to 25% of survivors. The pattern is familiar, with 50% of long covid patients suffering serious organ damage and 30% being severely disabled after 6 months: "long haulers" on Earth follow a pattern familiar from other post-viral syndromes (eg. CFS) and may be impaired to the point of being unable to work for years or decades.
COVID70 is highly contagious, many carriers are asymptomatic, and it was spreading in close quarters for up to 11 days before anybody realized it had arrived.
However, there is some hope due to peculiarities of architecture on Mars. All rooms have pressure control, and where a hospital on Earth would have fire doors, a hospital on Mars has emergency airlock doors. Habitats in a Mars colony by default have to be able to lock down in case of a depressurization accident, and are compartmented like a submarine. Finally, per-room breathing gas control makes nursing support for patients much easier than on earth—you can crank the partial pressure of oxygen in the ICU right up (as long as you stay below roughly 28%, above which even waterlogged organic tissue is potentially inflammable).
An mRNA vaccine for SARS-CoV-70 is available off-the-shelf on Earth. Problem: Hohman transfer orbit windows are biennial, and the next one won't open for another 15 months or so. The hospital and university have limited flexible manufacturing capacity for mRNA vaccines—they're in constant demand, because they're highly effective against most cancers and cancer is a persistent health threat in the relatively high-radiation environment on Mars.
Figures: 60% of the population will suffer from cancer at some point in their lives, compared with 30-40% on Earth. Most cancers can be treated with a course of mRNA shots that teach the patient's learned immune system to recognize the cancer clone. 0.5M people ➙ 300K cases over 75 years ➙ the colony requires capacity to manufacture at least 4000 treatment courses/year, as a routine baseline for survival. So there is a vaccine factory and local expertise, and this can be scaled up, but to provide a COVID70 vaccine for the entire Martian population within a year would require at least two orders of magnitude more output.
So their choices are (a) wait 15 months for the vaccine shipment (and upgraded vaccine factory) to arrive from Earth, or (b) divert resources into lockdown, contact tracing, nursing, and jerry-building an emergency vaccine factory from equipment/expertise/parts on hand.
Oh, and note those 90 day crew rotations to the outlying fuel, refinery, and mining plants outside the city limits ...
Some additional parameters
(I will add to this section as other stuff occurs to me. Check back often!)
The UK in 2020 operates a very lean medical service that employs roughly 1.8 million people out of a population of 68 million. 1 in 40 is thus a low-ball estimate of the proportion of the Mars population who will be working in one or another area of medical practice—nursing, surgery, pharmacy, lab diagnostics, nutrition, general practitioners, physiotherapy. That means Mars General Hospital and satellite facilities employ about 12,000 people.
COVID family viruses kill roughly 1% of the total population, but health workers and school staff are disproportionately affected, with mortality/morbidity running at 300-500% of baseline.
COVID70 will, if unchecked, kill roughly 5000 martians ... but perhaps 500 of them will be doctors and nurses. Training new doctors/nurses is a 7-10 year process, and recruiting on Earth may be difficult in the wake of a pandemic hitting a closed environment.
The colony will be left with a legacy of maybe 50-60,000 disabled colonists, of whom perhaps half will recover in 3-9 months: the rest are extreme long-haulers. Repatriating the disabled back to Earth is not an option (many of the invalids would be harmed or killed simply by landing on a high-gravity world, after spending years or decades on Mars). You're going to have to work out a social policy for handling dependents. In contrast, the colony age distribution resembles contemporary China emerging from the one-child-per-family decades rather than any historic high birth rate/high death rate colonial model. Growing your own doctors and nurses—or care home workers—is a very long term project.
You are the Mayor of Armstrong City, facing a variant SARS pandemic, and supplies and support are 15 months away. What do you do?
Alternatively: what are the unforeseen aspects of a SARS-type disease infiltrating such a colony?
And what are the long-term consequences—the aftermath—for architecture and administration of the Mars colony, assuming they're willing to learn and don't want it to happen again?