(Reuters) - Disruptions from the Feb. 21 hack at UnitedHealth Group's ( UNH ) tech unit created a cash crunch for small healthcare providers and led to a U.S. health department probe into whether there was a breach of protected health data.

The exact impact of the hack on patient data is not yet clear, but it adds to the growing list of increasingly disruptive cyberattacks on U.S. healthcare companies.

The following is a list of the biggest IT hacks in the sector where patient data were breached:

Type of

Name of Year Individuals company

company affected

Anthem Inc 2015 78,800,000 Health insurer

American 2019 26,059,725 Medical debt

Medical collector

Collection

Agency

HCA 2023 11,270,000 Hospital operator

Healthcare

Premera Blue 2015 11,000,000 Health insurer

Cross

Excellus 2015 9,358,891 Health insurer

Health Plan,

Inc

Perry 2023 8,952,212 Medical transcription

Johnson & service provider

Associates

(PJ&A)

Managed Care 2023 8,861,076 Dental insurer

of North

America

(MCNA

Dental)

Welltok Inc 2023 8,493,379 Healthcare technology

provider

23andMe 2023 6,900,000* Genetic testing

company

PharMerica 2023 5,815,591 Healthcare Provider

Corp

Source: Government data, company reports

Note: Hackers gained access to 14,000 customer accounts on the 23andMe website. From those 14,000 accounts, hackers accessed non-health information, such as names of about 5.5 million customers' relatives and 1.4 million customers' extended family members.

(Reporting by Sneha S K and Mariam Sunny in Bengaluru)