Yep. Greencough.

Hollypaw's eyebrows (yes, I know cats don't have eyebrows) rose and her eyes were full of concern for the toms, but nodded and left. She softly called over her shoulder, "Bye..."

Thornclaw attempt to block his coughs with his tail

Blazingpaw suddenly felt sad. "Bye Hollypaw," he called after her. He watched her as she dissapeared from view. He sighed and turned to Thornclaw. "Thornclaw, I think you're sick," he said as raspy coughs broke free from his mouth, causing his body to shudder. He started grooming his friend again.

((Just realized its Thornfang xD))

Thornfang coughed again and siad "No cant be" even though he new it couldnt be true that he was not