During previous Survival events, it used to be that the shorter zombie strains with fewer than eight stages could bite before their last stage, i.e. before they were unlocked as skins in the wardrobe. Currently this isn't working and strains with six stages cannot bite on stage five even though the FAQ states we should be able to bite on their last two stages (both stages five and six).
I will update the FAQs shortly. Since the strains were shortened, you can start biting around the same time as with other viruses. It is possible that this may change in the future, but I confirmed with a programmer that it will remain as is for this year.
Dexter by ❤
Thanks! I discussed it with a few other people and the consensus was the we used to be able to bite on stage 5 of shorter infections (such as the 2010 ones) so I hope it can be changed back to that way again at some point. If not though, we can live it with it. I appreciate the clarification :D