How Infections Spread in Outer Space


Out in space doesn't seem like a place you'd get sick. There aren't a lot of bugs out there. In fact, we don't know of any life forms - even microbial - that are native to out in space.

As people around the world contemplate traveling to Mars, we should think about what infections they may get in the process. 

First things first, we haven't found any diseases that come from Space. The rovers and robots we send to Mars and the Moon - and even Venus, search the soil, looking for any sign of life, any tiny microbe.

There haven't found any. 

Space doesn't seem to have any viruses, parasites, fungi, or bacteria that we know of. The sort of virus we think of on the Space Station are computer viruses

There are still pathogens in Space

Every time we send something into Space, however, we send along hitchhikers. The people (and things) we send can have tiny microbes hitching a ride.

Being in space can makes infections spread more easily

Not just do we send microbes into Space, but these microbes can spread more easily in space.

In Space, our air and water are recycled and conditions are crowded. This actually can promote the transmission of infections. Filters could help but some of these use up much needed energy.

On earth, we rely on earth's gravity to throw microbes to the ground after each cough or sneeze. Normally, tiny droplets spread respiratory infections. Diseases spread by droplets, like many respiratory viruses and colds, might travel 3 meters and fall to the ground in 10 seconds.

Airborne infections, like TB or chickenpox, can stay aloft for much, much longer.

Micro-gravity in a Space Station does not throw these tiny particles down to the ground. In space, each droplet you sneeze/cough/talk out can remain floating, weightlessly, indefinitely. This means you don't need to stand close to someone to get infected.

Infectious material can persist in the air much longer. You can be infected long after someone sneezes by an infectious particle that keeps floating around you.

(The same is true for odors which persist). 

These pathogens change when they're in Space

Not only do we send microbes into Space and they may more easily infect us, but these pathogens may sometimes change in ways that worry us.

Space affects us. Astronauts can float. Microgravity leaves their bones and muscles weakened. Radiation can affect their genetic material. Fluid redistributes, making faces and necks puffy.

Microbes are also affected. They may grow in large - and specially organized - clumps, which we call biofilms. These biofilms are thicker which would make it harder for antibiotics or our immune cells to penetrate and control bacteria.

Some bacteria can withstand the radiation. Some mutate. Some withstand mutation. Those that do mutate - bacteria, viruses, and even viruses that attack bacteria - may become bacteria we aren't as familiar with. This might not be a problem and it might not happen much, but it could change some enough so that our treatments wouldn't work. 

We change when we're in Space

Not only are there microbes that may be new and more easily infect us, but we are not as good at fighting them off in Space.

Our Immune System also changes. It becomes a bit unregulated. The system of cytokines and T cells and all of the immune messaging and fighting cells gets a

Space Travel can also be stressful. It is stressful to be away from family and friends, in cramped quarters, with microgravity, and with a job that requires precision and where decisions might even mean life or death. Their bodies show signs of stress response with high cortisol levels, which can affect immune responses. With all of this stress, sleep deprivation can also make astronauts more prone to infections.

Astronauts can have viruses inside of them, otherwise causing no problem that reawaken and reactive.

Their immune systems stopped controlling these viruses that usually cause no problems. We carry lots of viruses inside of us that usually cause us no problem. Some of these - like herpes - can reactivate and cause us problems. This happened with Chickenpox (Varicella) which was found to reactivate and be found in the saliva of multiple Astronauts (30% or more). It has also happened with CMV and EBV.

This might also mean that astronauts won't be as capable of fighting off new infections. An infection from on astronaut might spread to companions whose immune system guard is down.

It's hard to reach for help

When out in Space, there is a messaging delay. You can't call the doctor and have an immediate response. The delay is around 15 minutes between when you send a message and the doctor would receive it on earth.

A longterm human trip to Mars may be even more complicated than rockets and payloads.

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