We haven't seen a lot in terms of biological weapons in the world of One Piece, but this changed recently in the latest issue of the manga.
Luffy and other members of the Straw Hat Pirates landed in Wano Country with the primary purpose of freeing prisons who have been captured by the Shogun. Things took a wild ride after a member of the "Beasts Pirates", began firing a hail of bullets towards them.
The team soon finds out that these bullets have biological compounds, and were made by Queen, another member of the Beasts Pirates.
From what we can tell, the bullets from this gun is mixed with a biological agent that gives the enemy a dangerous flu-like virus. Were not sure if it kills, but we do know it slows down anyone it comes in contact with.
For those who are wondering, the Beasts Pirates are a three-member team. They consist of Jack, Queen, and King. Out of all the three villains, Jack is the most dangerous. Furthermore, this team works for Kaido the Dragon, the very man who aims to defeat Luffy and his Straw Hat Pirates.
Time will tell if Luffy and the gang and escape this new problem, or face the obvious consequences if they don't.