Diphtheria

Balto
A huge number of kids were sick from this and also Jenna's owner was a victim of this sickness, Balto tries helps her to know the answer and once he did Jenna thanks him, later, the sled team were sent to receive the cure but they were lost for awhile. Everyone were slowly losing hope and Balto wanted to do all he can to save her but Steele made it impossible to do so. Once he succeeded, all the town thank Balto for his brave action.

Trivia

 * When the person was building the wooden coffins, that hinted the real event on how some of the kids actually died during the events.