It is a pretty cool idea but as pass said there are a lot of flaws.
A couple suggestions I have that I think could make it a bit better.
Make the first infected basically the "Alpha" infected. Give him 250hp and make him sliiightly faster than the average player or give him some sort of sprint ability.
Another thing is make a few people start off with no items, and maybe 1 in every 8 or 9 players start off with a slow rof but high (90) damage gun. It would add a bit more variety, preferably a slowish bullet, too, not hitscan.
Also add map borders for the love of god, I was playing earlier and every round some annoying jerks would just run out of the map forever and delay the round way longer than it needed to be. So while speaking of delaying rounds, make it so every time someone gets in the helicopter it shaves a few seconds off the leaving timer, a lot of rounds where the normal players would win there would be that guy that sits outside the heli until it leaves and then jump in, forcing EVERY PLAYER IN THE SERVER to wait way longer than necessary for the round to reset.
And then like port said if the players kill the first victim just give them all a couple points and reset the round.
