For years, the lines were pretty clear in health-care services. There were the providers: hospitals and doctors that provide medical care. Then there were the payers: the insurers who wrote the checks for the health-care claims.
Now the lines are increasingly blurred, with new ventures, nontraditional players merging, and major health-care leaders expanding into new sectors.
UnitedHealth Group remains the largest insurer by membership, yet through acquisitions it has built a data analytics and pharmacy benefits business under its Optum division that is the driving force of its growth. In addition, it has bought up hundreds of physician's practices and now employs more than 30,000 doctors — thousands more than some major hospitals.
"We look very different today than five years ago — for example, clinical and technology professionals are the first and third largest job categories across UnitedHealth Group — and we will look different again five years from now as we continue to evolve at an accelerated pace," UnitedHealth CEO David Wichmann said on the company's first-quarter conference call.
United's largest competitors aim to look different, as well. Cigna CEO David Cordani says we shouldn't think of his firm as an insurer, anymore. Cigna's $69 billion deal for pharmacy benefits firm Express Scripts is about moving beyond old health-care models.
"Is your model going to embrace and expand choice, or not? Is it going to improve and drive value through affordability, or not?" Cordani asked at CNBC's Healthy Returns conference last month. "We're excited about that conversation because we're excited about being a continued force for disruptive change."
CVS' $57 billion deal to buy Aetna aims to create a new hybrid model. Beyond combining medical and pharmacy benefits, providing primary care in CVS' retail clinics is a big part of part of the strategy behind the deal.
So, what do we call all of these new and novel hybrids, if these deals come to fruition?
"One way to look at it, is just to think about functions," said Trine Tsouderos, PwC's Health Research Institute director. "We think they fall into four buckets ... (starting with) employer-activists."
PwC puts the new venture between Amazon, Berkshire Hathaway and J.P. Morgan in that activist model. The three firms aim to leverage data and technology to shake up the traditional employer plan model.
Amazon also falls into PwC's second category: technology-invaders. These are often large tech firms looking to partner with traditional health-care players on new platforms, such as Apple's initiative with hospitals to allow patients to have health records on their phones.
PwC calls the third new breed the integrators — firms like UnitedHealth, Medicaid insurer Centene, which has also bought up provider services, and Cigna-Express Scripts.
These are "companies that are trying to get as many pieces of the overall puzzle together that they can offer the consumer ... from insurance … to your knee surgery," Tsouderos said.
"Then you've got health retailers … retail-focused companies that are able to reach consumers on many different levels and offer a whole swatch of health-care products and services," she said.
CVS-Aetna is squarely in the retail camp. Sources tell CNBC Walmart has also explored expanding its health-care partnership with Humana beyond Medicare drug plans.
All four models are predicated on cutting out the middlemen to bring down costs for the companies and their customers.
In health care, however, new models take time to take hold. It's hard to disrupt the regulatory complexity of the business.
For nearly a year Amazon explored how it could be a tech invader in the pharmacy market, only to put the effort aside for now, according to sources familiar with the situation.
Jeff Bezos may have put it best, in his annual letter to shareholders, when he talked about defining the right scope for success in a business.
"Unrealistic beliefs on scope — often hidden and undiscussed — kill high standards," Amazon's founder wrote. "To achieve high standards … you need to form and proactively communicate realistic beliefs about how hard something is going to be."