PRRSv causes significant profit loss when a herd is infected, so it is important to have strategies to avoid infection, or eliminate the virus from a herd. Infected pigs are the main cause of introducing the virus to a herd, but contaminated gear or items, water supply, or even airborne methods are possible. Air filters for the intake air are effective at keeping the airborne virus out, but other biosecurity methods are necessary as well. Once the virus is in a herd, controlling it is important, especially to avoid infecting sows with contaminated boar semen. The McRebel concept can be used to control the spread in suckling pigs, and various gilt acclimation methods can provide immunity before introduction to the sow herd. Live virus vaccines can reduce mortalities; although, the effectiveness of inactive vaccines is not confirmed. Elimination of the virus from a herd can be done by test and elimination, depopulation/repopulation, or herd closure. The Stevens County program has shown that regional control is possible, and has resulted in other regional studies being conducted. If enough sparse regions are controlled, dense hog areas may be better able control or eliminate the virus spread as well.