In S2E8 of Supergirl, Cyborg Superman deployed an aerosol weapon in a bar, which caused all of the alien patrons to die while all of the human patrons were unharmed.

Supergirl learned from a hologram of her father at the Fortress of Solitude that the weapon was the Medusa virus:

Medusa, a weaponized virus that I created for the defense of the planet Krypton. It was a joint partnership between the Science and Military Guilds. We bio-engineered the virus to attack non-Kryptonian physiology. In the event of an invasion, Medusa could be deployed to kill alien combatants while keeping our civilians and infrastructure safe from harm.

Supergirl later explained to the DEO:

Henshaw stole the virus's formula from the Fortress of Solitude, which means Cadmus can make as much of the virus as they want. An unstoppable bio-weapon that kills every alien except Kryptonians.

Later in the episode, right before the weapon was to be deployed on a wide scale, Cadmus broadcast a message indicating that the virus would kill all aliens except humans:

Tonight, every alien who has stepped foot on our planet will die. Because Earth is for the humans. The future is for the humans.

But if the virus attacks all non-Kryptonians, then shouldn't it kill humans too?

  • @pacoverflow. +1 as I had the exact same thought when I watched the episode. I think Paulie_D is correct. Cadmus must have figured out how to change the virus to exclude humans as well as Kryptonians. But, that wasn't explicitly called out in the episode and is a legitimate question if it was simply an unstated assumption or a real oversight/goof.
    – beichst
    Dec 4, 2016 at 16:17

1 Answer 1


It's not explicitly stated but it's a reasonable assumption that Cadmus re-engineered the virus.

Eliza states that the Medusa virus is easily weaponised.

The Medusa virus was so easily weaponized I was able to turn it against a common enemy, J'onn's White Martian blood cells.

Cadmus has all the necessary information from the Fortress of Soliture on the creation of the virus AND their own considerable scientific expertise to not only synthesize the virus but also weaponize/re-engineer it.

Then they field-tested it in the bar...a small scale test, to be sure, but nonetheless, a test.

That the virus is readily adjustable is evident from the fact that Eliza goes on to re-engineer it again to create a cure for BOTH Mon-El and The Martian Manhunter in less than 24 hours.

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