Length seems about right for a Teaser, it was an easy page to read. Only thing I want to pick at is around the sentence where the locals call it "Blue Madness" I think there should be a more specific description of why they call it that, instead of a paragraph later as it's harder to work out what plant-matter is part of that custom. I had this idea it would be like mold (instead of moss) and have deep blue veins, or if it's like bioluminescent cups (when it gets described as mushrooms.) Covers a fair bit of world-building and there isn't enough post-apocalypse fiction that have plants as the downfall.

Also just to check, Lemmy is the hyena and Zeek is the fox? Just realized I can double check this by looking at your avatar. You've been using 'the hyena' and 'the fox' as placeholders for the characters' name, but I think it would make the story stronger and their names better able to stick to in the readers minds to their respective species by describing them more. Where you say the masks itch after a while, you can have the character think of how it makes their hair -of a very distinct colour- feels matted, or describe the colour of their fingers as one of them checks the filter. I have this mental image that the hyena's would be brown, the Fox's black. It's easier to follow the dialogue as it's a to-me-to-you format, but with exposition less so.

Just by safety precautions (masks on) and the two's reluctance to deal with the mushroom pit of doom, and the state Andy (if that's who it really was) was found in. The Fungus feeds on the living? I would be retching too, that is a horrible way to go, ontop of dying in a ditch. I could love where this is going.

Pretty much what I could say has already been addressed by Zinn above. Definitely a good length for a teaser, as Im now itching to read more! This "Blue Madness" kinda sounds familiar in concept to the Blight in Cherie Priest's Clockwork Century series which I would suggest giving a read if possible.