People questioned that immortal Loew and Reload happily slaughtered the other astronaut with N5S.
If you look at p.29 in ch42, you can see little particles flying through the air, a bit like snow.

I think these are the spores which transmit N5S, you see them in chapter6, p.17 as well.

And in chapter 12, p.18, the "mother", Dr. Kurokawa´s daughter, explains in the tutor:
"Now people cant live on mars anymore."

Thats probably because the whole atmosphere is full of the N5S spores.

So there was no need for Reload or Loew to infect the other astronaut. All the DRF had to do, was not telling them of the hazard and once the astronaut enters the spaceship the spores would infect him.