Here's why:
* Short vowel sounds are typically quick and sharp. The "i" in "virus" makes a short, sharp sound, similar to the "i" in "sit" or "pin."
* Long vowel sounds are typically drawn out. The "i" in "virus" is not a drawn-out sound like the "i" in "bike" or "time."
So, the "i" in "virus" has a short vowel sound.