The chance of a particle escaping depends on its mass. That's why helium escapes pretty fast. The other gas molecules still escape, but far far slower. The

The chance of a particle escaping depends on its mass. That's why helium escapes pretty fast. The other gas molecules still escape, but far far slower. The Maxwell Boltzmann distribution applies. Something like a virus is far far heavier again, so the rate of escape would be miniscule. Not sure if it's small enough to have never happened across the surface of earth though.