Soldiers infected with more virulent strains were more likely to be shipped to military hospitals, while those infected with less virulent strains were more likely to remain in the trenches.

The military hospitals were much more active vectors of transmission than the bays of the trenches, so the normal pattern of transmission was inverted, with the more virulent strains spreading faster than the less virulent ones.

Under normal conditions, the very sick would stay home while the less sick would go to work, which would tend to push highly virulent viruses toward becoming less virulent over time.

Even if all seats are full they dont make earth shaking profit that cant be avoided. The economy doesnt require doing it. The risk benefit ratio is off the chart.

People making such decisions should really be behind bars? I cant think of a better way to kill. Just send some plague ships and it will make short work.