Typhoid, pneumonia, diphtheria, spotted fever were doing their work in the raw, unacclimated regiments.

Regimental medical officers were exhausted.
Two steady streams of human beings, flowing in opposite directions, had set in with the autumn; the sick, going North, the new regiments arriving from the North to this vast rendezvous, where a great organizer of men was welding together militia and volunteers, hammering out of the raw mass something, that was slowly beginning to resemble an army.
Through the wards of their hospital Ailsa and Letty saw the unbroken column of the sick pass northward or deathward; from their shuttered window they beheld endless columns arriving--cavalry, infantry, artillery, engineers, all seeking their allotted fields or hillsides, which presently blossomed white with tents and grew blue and hazy with the smoke of camp fires.
All day long, rain or sun, the landscape swarmed with men and horses; all day long bugle answered bugle from hill to hill; drums rattled at dawn and evening; the music from regimental and brigade bands was almost constant, saluting the nag at sunset, or, with muffled drums, sounding for the dead, or crashing out smartly at guard-mount, or, on dress parade, playing the favorite, "Evening Bells." Leaning on her window ledge when off duty, deadly tired, Ailsa would listen dully to the near or distant strains, wondering at the strangeness of her life; wondering what it all was coming to.
But if life was strange, it was also becoming very real and very full as autumn quickened into winter, and the fever waxed fiercer in every regiment.
Life gave her now scant time for brooding--scarce time for thought at all.

There were no other women at the Farm Hospital except the laundresses.

Every regiment in the newly formed division encamped in the vicinity furnished one man from each company for hospital work; and from this contingent came their only relief.
But work was what Ailsa needed, and what Letty needed, too.

It left them no chance to think of themselves, no leisure for self-pity, no inclination for it in the dreadful daily presence of pestilence and death.
So many, many died; young men, mostly.