Pharmacies across the country are running into issues filling prescriptions due to a cyber incident affecting a multibillion-dollar healthcare conglomerate involved in processing half of all medical claims in the U.S.

Nashville-based Change Healthcare first announced disruptions to certain applications early on Wednesday, before saying in the afternoon that the company was “experiencing a network interruption related to a cyber security issue.”

On Thursday, it issued another update, saying: “Once we became aware of the outside threat, in the interest of protecting our partners and patients, we took immediate action to disconnect our systems to prevent further impact.”

In 2022, Change Healthcare completed a $7.8 billion merger with the healthcare services provider Optum, a subsidiary of UnitedHealth Group.

In its notice about the incident, the company said the issues are “specific” to Change Healthcare and do not affect “other systems across UnitedHealth Group.”

Pharmacies took to social media on Wednesday and Thursday to warn customers of issues processing prescriptions. Lone Star Pharmacy in Santa Fe, Texas, wrote on Facebook that they were “currently unable to process any prescriptions on insurance due to a software issue.”

“No ETA on when it will be fixed. Please be patient and wait for your text message notifying you that your prescription is ready. Sorry for the inconvenience!!!!”

Another family pharmacy in Albion, Illinois, wrote about the “fiasco.”

“Apparently, the ‘switch’ that controls about 70% of the nations pharmacy insurance claims had a cyber attack, & they shut down the server,” they said, referring to the software that serves as an intermediary between pharmacies and insurance companies.

Based on the long list of affected services mentioned on Change Healthcare’s website, it is likely that other important cogs within the healthcare industry have been impacted by the outages. The company said the disruption “is expected to last at least through the day.”

The healthcare industry has been a popular target for hackers, including for the LockBit gang, whose infrastructure was seized this week in a global operation. The healthcare software firm ILS was targeted in March 2023 and earlier this month a breach at two insurance companies resulted in the leak of healthcare data belonging to more than half the French population.