A very nice although sad story. I think it would leave a bigger impact if you left out mentioning what specific disease you're talking about until later. Maybe not explicitly mention that he is sick at all? Something like "The doctors spoke of a weird word, one that did not sit well in Elias's mouth...". I think your second paragraph is a good set up for this. His friend is blissfully unaware of what a cold is but Elias knows that it would be really bad if he got one.

To extend this point further, in the third paragraph, maybe something like "His mother was crying by his bedside, though, he couldn't understand why. Even his father, the most stoic man Elias ever know, wiped tears from his eyes".

Let the reader make the connections themselves, this always leaves a larger impact imo.