Last year, the COVID-19 pandemic caused severe supply disruptions for Arctic research expeditions. If I'm reading this article right, at least one team had every single resupply trip cancelled! (See the comments for more details, and a discussion of possible tension with this documentary.)
Ships from across the world that were scheduled to make journeys to the Arctic to exchange crews and drop off supplies cancelled their trips. The scientific crew in the Arctic at the time were forced to stay two months longer than originally planned.
And in the end no ship was able to make the journey north. In May, scientists finally left the Arctic on the same ship that had been their hotel and laboratory since the beginning, the Polarstern. That ship was supposed to stay in the Arctic for the entire expedition.
Even resupply trips to Canadian Arctic towns took tremendous effort to carry out safely.
COVID-19 is awful, but it's easy to imagine things much, much worse. A worldwide outbreak of the wrong disease could make crewed or even uncrewed resupply trips unacceptably dangerous to the colonists, the resupply crew, or both.
Consider, for example, an airborne fungus that can lie latent in the lungs for up to four months before erupting into an active infection, which starts with a week or more of asymptomatic transmission, and ends with death in 25% of cases. In addition to wafting from person to person, its spores can settle on surfaces indefinitely before being kicked back into the air. Various combinations of cleaning techniques seem to help reduce its spread, but no practical procedure has been shown to decontaminate air or surfaces with high confidence.
If that disease went pandemic, it would be very hard to put together supply packages that colonists could safely bring into their living areas. 225
That would cut off delivery of food, medicine, agricultural inputs, materials for indoor construction, and air-monitoring equipment to detect the fungus.
It could even be risky to send equipment that stays outdoors. The colonists would have to touch the equipment to use or maintain it, and then they'd re-enter the living area, using procedures that weren't designed to keep out anything finer or more dangerous than Martian regolith. If the spores turned out to survive well on regolith, they could make the areas around equipment drops untrustworthy for years to come.
The colonists' tolerance for infection risk would be extremely low, because the consequences of an outbreak would be disastrous. If spores got into the living area, they could spread through many rooms before the colonists noticed them. Because of the disease's infection dynamics, an outbreak could incapacitate or kill many colonists over a short period with little warning, disrupting day-to-day survival operations. A supply cutoff would make life very hard for the colonists, but an outbreak could wipe the colony off the map, and possibly turn it into a long-term biohazardous graveyard.
As the colonists and their support teams on Earth race to design and implement a safe resupply system, they'll both be hobbled by grave immediate threats. If the scale of the pandemic only becomes apparent in the months before a major resupply launch window, a whole wave of deliveries will have to be cancelled, and the colonists will be scrambling to prepare. Meanwhile, the people on Earth will need most of their resources to face the medical, logistical, financial, political, and emotional horrors of the pandemic, from national governments down to individual support employees. It could take a year or more just to learn enough about the fungus for meaningful risk estimation, another year for design and testing, and who knows how long to scrape together the labor, materials, and political will for construction and launch? Waiting for a good launch period will take even longer; launching from a bad window will cost even more. 197