A cyberattack on California-based Prospect Medical Holdings has resulted in the closure of emergency rooms and the diversion of ambulances in several states. The attack, which began on Thursday, affected hospital computer systems in California, Texas, Connecticut, Rhode Island, and Pennsylvania. Prospect Medical Holdings took its systems offline to protect them and launched an investigation with the help of third-party cybersecurity specialists. The company is currently focused on addressing the needs of patients and returning to normal operations as quickly as possible. In Connecticut, the emergency departments at Manchester Memorial and Rockville General hospitals were closed for a significant portion of Thursday, with patients being redirected to other nearby medical centers. The Eastern Connecticut Health Network, which runs these facilities, reported that while the emergency departments reopened late Thursday, many primary care services remained closed on Friday. Elective surgeries, outpatient appointments, blood drives, and other services were also suspended. The FBI in Connecticut is working with law enforcement partners and the affected entities to investigate the incident. Similar disruptions were reported at other facilities across Prospect Medical Holdings' network. In Pennsylvania, services at facilities including the Crozer-Chester Medical Center, Taylor Hospital, Delaware County Memorial Hospital, and Springfield Hospital were affected. Waterbury Hospital in Connecticut is utilizing downtime procedures, including the use of paper records, until the situation is resolved. Prospect Medical Holdings has seven hospitals in California, including two behavioral health facilities and a 130-bed acute care hospital in Los Angeles. Messages sent to representatives for these hospitals have not been returned. Prospect Medical Holdings is currently working with IT security experts to resolve the issue as quickly as possible. The extent of the data breach and the impact on patient data and privacy is still being determined as the investigation continues.