[ WP ] What 's the catastrophe that finally brings humanity together ?

We had to burn Them, we had to burn Them all. All of our fathers, sisters, cousins, and friends down on Earth gone, turned to ash by the atmosphereic blaze. Any that survived, well, there won ’ t be a lungful of oxygen left on the surface for them. Earth, Terra Firma, The Third Planet, Earth, Home, all names that mean so much to us. We were the children of our world who left to explore others, we were the ones who build the lunar cities, the Martian colonies; we drilled Titan, and excavated methane and hydrogen from comets and asteroids. We were the wandering children, striking out on our own to find our fortunes in the vast blackness, hoping to bring that wealth back home. We wanderers and adventurers all left our home for various reasons; wealth, adventure, glory and desperation called to men and women, pulling us in to the void. Now as much as we idolized it we all knew Earth was far from perfect, and on some level we all fled to leave something behind. We left racism, nationalism, and Earthly disputes on Earth. But we all came back to our flawed home for one reason. 
 
 They called it the virus virus, or V2 in the news. It was a particularly nasty infection that caused rapid destruction of cells among other things. People who believed them selves to be healthy would wake up and find the meat of their limbs dissolved in to a bloody, viral soup. The last straw came when we found that V2 could infect other viruses, suddenly the common cold, HIV, and every other contagious virus became a carrier. When that bombshell hit the news, all flights were canceled, Luna Prime refused arriving rockets, and Earth borders were closed but it was to little too late. 
 
 We heard about the spreading infection, the riots, the deaths of world leaders, and the sickness on the hyperwave net. We watched videos of doctors explaining the infection vectors, we sat wide eyed at experts proving that V2 was not a bioweapon, and we sat teary-eyed as the remains of the UN sent out a call: “ men and women of space, Earth ’ s children, come home and help heal our world ”. 
 
 Most anyone reading this after today will be a spacer, and so they will understand, but if somehow you, reader, have never been off world then you will not truly follow our logic. On a spacefaring vessel the crew breathes the same air, drinks the same water, and shares the same space. Everything is recycled. What is more important is that everyone on the crew has duties. Disease can kill ships, if a crew is sick and cant respond to an alert, the ship explodes, crashes, or burns out. We fear disease more than death out here in the inky void of space. 
 
 So imagine our horror when we find that Earth has become a breeding ground for the worst disease in the history of mankind. Imagine the horror that we feel when our families expect us to come home and die with them. Imagine the horror of the though of some infected bastard sneaking off world in a rocket, evading the quarantine measures and infecting Luna City, or any of our other new vulnerable homes. 
 
 So we protected ourselves, our fleet descended in to the upper atmosphere and triggered our FTL drives, setting everything ablaze, and we the children of Earth flew off into the abyss again, united in our suffering, united in our loss, and united in thoughts of a home lost to fire. 
 
 EDIT: i a word 

