Recently, in my Julii campaign, my army in the Balkans was on the verge of taking Larissa, leaving Macedonia with only one settlement left. I was trying to beat the Brutii to the Balkans but this plague has allowed them to almost gain an advantage there, which can screw me over when the Civil War comes.
wow deedeedee when you take over Macedonia every city it had/has you have to massacre the people so you can prevent this but if you didn't build sewers, and upgrade those sewers to public baths, etc you are screwed and make sure you build a shrine that promotes health benefits OK
The plague will leave the city by itself after a couple turns. Just wait it out. If you build some buildings that promote health such as those of sewers and public baths, you'll have less of a chance to get the plague, but the plague doesn't really come along that often anyhow.
Also, don't do anything with those cities that are under the plague. Don't move units in, don't move units out. Wait until that skull icon leaves the province viewing screen and make sure any family members don't have that skull icon either. After that's gotten rid of, you can start moving troops around again.
You can purposefully put spies in your plagued settlements so they get the plague and then send them off to enemy settlements as a sort of biological warfare, but don't do it to cities that you're about to take over since the plague lingers.
The plague will disappear by itself after a random amount of time. Building health buildings will not prevent or reduce the duration of the plague. If a particular settlement is not recovering from the plague, it may be the result of an enemy agent coming in and out of your settlement.
There is no way you can prevent plague, even building sewage or health building. They will only reduce the chance of having plague. Once you reach over 30,000 people in your cities, the plague will occur randomly. You should not garrison your army in the cities, except peasants.