An Ascension spokesman said “unusual activity” was detected on its computer network Wednesday and that both its electronic health records system and its MyChart system, which gives patients access to their records and lets them communicate with their doctors, were down. The St. Louis-based Catholic health system operates 140 hospitals and about 25,000 beds across 19 states and the District of Columbia. Ascension’s statement said ambulances were being diverted from “a limited number” of its hospitals, but it did not identify them. “We have determined this is a cybersecurity incident,” the spokesman was quoted as saying in the statement, adding that “the investigation and remediation efforts will take time, and we do not have an estimated time of restoration.” Cybersecurity experts say there has been a sharp increase in ransomware attacks in recent years, particularly targeting the health care sector. Increasingly, criminal groups are stealing data before activating the encryption software that locks up computer networks. The threat of releasing the stolen data is used to extort payment. The data can also be sold. Earlier this year, a cyberattack on Change Healthcare disrupted health care systems nationwide after hackers gained entry to a server that lacked multifactor authentication, a basic form of security. Change Healthcare, which is owned by UnitedHealth Group Inc., provides technology used by doctors and other health care providers to submit and process millions of insurance claims each year. The attack delayed insurance reimbursements and put a strain on medical offices around the country. UnitedHealth CEO Andrew Witty told Congress earlier this month that it paid a ransom of $9 million in bitcoin, but that the company’s core systems are still not fully operational. Read Also: Ursula von der Leyen denuncia ciberataque contra o seu 'site' de campanha (Portuguese version)