HbsAg testsforthepresenceofthehepatitisBvirus.A"positive"or"reactive"HBsAgtestresultmeansthatthepersonisinfectedwiththehepatitisBvirus,whichcanbean"acute"ora"chronic"infection.Infectedpeoplecanpassthevirusontoothersthroughtheirbloodandinfectedbodilyfluids.