So, you’ve just purchased some POL pullets, or rescued a small flock of somebody’s unwanted chickens. You can’t just throw them in with your current flock because that could be disastrous without a proper quarantine before integration or even attempting see but don’t touch. So… you keep them separated for 30 days and practice perfect biosecurity all while observing the new birds and never seeing any signs of illness. Now it’s safe to introduce them to your flock right? But, what if your new birds have previously acquired immunities and are merely carriers of something your current birds have no immunities against? Is that possible? Will your current flock now become infected? Get sick and die? In researching various diseases and viruses, I have become quite paranoid about how easily they can be spread. I’ve read threads here on BYC where folks have quarantined and still had illness and death brought into their flock. This whole business has me convinced the best way to add to your flock is to buy chicks from a hatchery where the risk of bringing in disease is practically nil. But what if your own chickens are carriers and then you bring in new healthy birds? How do you know when it’s safe?