Anthrax

This has GOT to be one of the scariest diseases around, shame my high school only mentioned it once.

There were/are several 'anthrax islands' around, with Gruinard Island being one of the best-known islands. Apparently, there are 0 inhabitants, as weaponized anthrax was being tested on this island on sheep. Within days, all animals died of respiratory distress and shock, showing anthrax's potential as a biowarfare weapon. They burned down the island to decontaminate it, but when they reintroduced sheep, anthrax quickly returned.
Sometime ago, they sprayed formaldehyde mixed with seawater on the island, and upon reintroducing a flock of sheep, no animals were infected with anthrax, making it a safe island again.

Bacterial/Viral/Fungal/Parasitic: Bacterial
Causative agent: Bacillus anthracis 
Incubation time: about 8 days
Antibiotics of choice: Ciprofloxacin
Toxins / Factors: Lethal factor (LF), Edema factor (EF), Protective antigen (PA) (AB)
Bioterrorism agent category: A
Vaccine available: Yes (Toxoid: contains inactive toxins)[1]