Breach filing
ArchivedMayfield Clinic Inc: 23,341 individuals, Apr 2016.
Mayfield Clinic Inc reported a breach of unsecured protected health information to the HHS Office for Civil Rights on 23 April 2016. The filing records the organisation as a healthcare provider in Ohio and lists 23,341 individuals affected, which makes it the 49th largest of the 276 Ohio filings on the register and the 44th largest of the 328 filings submitted nationally in 2016. Among the 13 Ohio filings made in 2016 it ranks 4th.
Individuals affected
23,341
As reported to HHS
Modelled cost (IBM 2025)
$3.73M
Method shown, not disclosed
Rank in OH
49th
of 276 Ohio filings
Rank in 2016
44th
of 328 filings nationally
Section F.1 / The filing
As posted by HHS OCR
Every value below is the portal's own field for this filing, plus its rank within the register.
- Covered entity type
- Healthcare Provider
- Individuals affected
- 23,341
- Breach submission date
- 23 April 2016
- Submission year
- 2016
- Type of breach
- Hacking/IT Incident
- Location of breached information
- Business associate present
- No
- State
- Ohio (OH)
- Portal status
- listed in the HHS OCR breach portal archive
- Rank in Ohio by size
- 49th of 276
- Rank in 2016 nationally
- 44th of 328
- Ohio median filing
- 2,763 individuals
- Register id (derived)
- OH-20160423-mayfield-clinic
Section F.2 / In context
Where this filing sits in Ohio and in 2016
OCR classifies the incident as a hacking or IT incident, with the breached information held in email. Hacking/IT Incident is the type recorded on 162 of the 276 Ohio filings (59%) and on 35% of all filings submitted in 2016. Email appears on 23% of Ohio filings.
No business associate is recorded on the filing; 29% of Ohio filings do involve one. At 23,341 individuals the breach is 8.4 times the Ohio median filing of 2,763 and 5.8 times the national median of 4,000 across all 7,884 filings. It sits in the 10,000 to 99,999 band, which holds 1,938 filings.
As of 28 August 2026 the case is listed in the HHS OCR breach portal archive. OCR's closing summary of the case is reproduced in full below.
Ohio's breach notification statute (Ohio Rev. Code 1349.19) requires notice to affected residents within 45 days of discovery or notification of a breach. Its attorney general threshold: no direct AG requirement (reporting agencies at more than 1,000 residents). The HIPAA Breach Notification Rule ran alongside it: notice to affected individuals and to HHS without unreasonable delay and no later than 60 days after discovery, which is the clock that put this filing on the portal.
Multiplying 23,341 individuals by IBM's $160 customer-PII cost per record (Cost of a Data Breach 2025, the figure the site's calculator uses) gives a modelled $3.73M; the 2026 edition's $192 gives $4.48M. Both are modelled estimates with the method shown, not costs disclosed by Mayfield Clinic Inc. For scale, IBM's 2026 average cost of a healthcare breach is $6.64M, so this filing models at 0.7 times the sector average.
Section F.3 / OCR closing summary
The portal's archived description, in full
Written by the Office for Civil Rights when the case was closed and reproduced verbatim from the HHS export.
An unauthorized person sent a fraudulent email with an attachment that triggered a download of a ransomware virus to 23,341 email addresses held by the covered entity's (CE's) business associate (BA) on its behalf. The protected health information (PHI) involved in the breach included email addresses. The CE sent an email notification to affected individuals on the day of the incident and sent another email notification two days later. The CE provided breach notification to HHS, affected individuals, and the media and also posted substitute notice on its web site. Following the breach, the CE assessed system controls, provided anti-scanning updates to its employees' email, deleted the email addresses it maintained on its BA's systems, and put a hold on the future electronic distribution of newsletters. OCR obtained written assurances that the CE implemented the corrective actions listed above.
Section F.5 / Modelled cost
23,341 individuals through IBM's per-record figures
Modelled cost / method shown, not a disclosed cost
ModelledIBM 2025 customer PII, $160 per record
$3.73M
23,341 x $160
IBM 2026 customer PII, $192 per record
$4.48M
23,341 x $192
Method: individuals affected, as reported by Mayfield Clinic Inc to HHS, multiplied by IBM's customer-PII cost per record (Cost of a Data Breach 2025 Figure 6 and the 2026 edition). No cost has been disclosed by the entity for this filing; the figure is a planning estimate, not a fact about the breach. IBM's per-record figures come from mid-volume breaches and IBM cautions against applying them to breaches involving millions of records; the site's per-record page explains where the multiplication holds and where it breaks down.
Context: IBM's average cost of a healthcare breach is $6.64M in the 2026 report ($7.42M in 2025); the global average across all sectors was $4.44M in 2025.
Cost per record: method and limits / Healthcare breach cost, IBM 2026
Section F.6 / Notification clock
Ohio statute and the HIPAA rule
State notification statute
Ohio: Ohio Rev. Code 1349.19
- Notice to individuals
- Within 45 days of discovery or notification of a breach
- Attorney general threshold
- No direct AG requirement (reporting agencies at more than 1,000 residents)
- Private right of action
- No: No direct individual lawsuits; AG may investigate under ORC 1349.191
- Penalty
- Escalating civil penalties up to $10,000 per day for intentional or reckless non-compliance
The HIPAA Breach Notification Rule runs alongside the state statute: notice to affected individuals and to HHS without unreasonable delay and no later than 60 days after discovery.
Section F.7 / Peer filings
Ohio filings closest in size
Neighbours by size rank among Ohio filings in 2016, topped up from other years where 2016 has too few. Filings of 10,000 or more link to their own page.
| Covered entity | Type | Individuals | Submitted | Breach type | Location | BA |
|---|---|---|---|---|---|---|
| Community Mercy Health Partners | Healthcare Provider | 113,528 | 25 Jan 2016 | |||
| Ohio Department of Mental Health and Addiction Services | Healthcare Provider | 59,000 | 22 Apr 2016 | |||
| Sunbury Plaza Dental | Business Associate | 7,784 | 21 Jul 2016 | |||
| EDWARD G. MYERS D.O. INC | Healthcare Provider | 6,441 | 10 Jun 2016 |
Index / Companion schedules
13 HHS breach register
→Hub: every filing, by state, year and entity.
04 Biggest breaches
→Mega-breaches with primary-source cost figures.
Industry / Healthcare
→IBM 2026: $6.64M average, 13 years at #1.
Regulation / HIPAA penalties
→OCR enforcement tiers and the 60-day rule.
11 50-state laws
→Deadline, AG threshold and penalties per state.
Cost / Per record
→Where the per-record model is reliable.
Provenance
Source: U.S. Department of Health and Human Services, Office for Civil Rights, Breach Portal (breaches affecting 500 or more individuals), retrieved 2026-08-28. Public domain. Individuals affected and dates as reported by the covered entity.
Portal: ocrportal.hhs.gov breach report. Statutory basis: HITECH Act section 13402(e)(4): the Secretary must post a list of breaches of unsecured protected health information affecting 500 or more individuals. Breaches affecting fewer than 500 individuals are reported to OCR annually and are not posted, so they are not on this register. Status wording follows the portal's two tabs ("Cases Currently Under Investigation" and "Archive") as of 28 August 2026; a filing moves to the archive when OCR closes the case. Modelled costs on this site are a method applied to the reported count, using IBM Cost of a Data Breach per-record figures, and are never a cost disclosed by the entity. This row: hhs-breach-archive__2026-08-28.csv, export row 5590.
Corrections: if you represent a listed entity and the portal row has been amended, email [email protected] with the portal entry and we will re-pull the export.