UnitedHealth isolated and disconnected the impacted systems "immediately upon detection" of the threat, the filing said. Change Healthcare offers tools for payment and revenue cycle management, and its system outages have disrupted operations in pharmacies and health systems across the country. UnitedHealth said late Monday night that more than 90% of the nation's pharmacies have set up modified electronic claims processing workarounds, while the rest have established offline processing systems. The disruption has not impacted provider cash flows yet since payments are typically issued one to two weeks after processing, UnitedHealth said Monday. UnitedHealth is the biggest health-care company in the U.S. by market cap, and it owns the health-care provider Optum, which services more than 100 million patients in the U.S., according to its website. Change Healthcare merged with Optum in 2022.