• Berkshire Hathaway's Todd Combs is leading the CEO search for the company's health joint venture with Amazon and JPMorgan.

• Candidates approached so far include former Medicare chief Andy Slavitt, former United States CTO Todd Park, and ex-Aetna senior executive Gary Loveman.

• Venture capitalist John Doerr has taken an informal role in the search as well.

Amazon AMZN , Berkshire Hathaway and JPMorgan Chase are searching for a CEO for their new joint venture to improve health care for their employees while lowering costs. The group is casting a wide net across the health care industry to find the right person, say several sources familiar with the search, who declined to be named because the details of the initiative are confidential.

Berkshire Hathaway's Todd Combs is taking the lead on the recruiting effort, several of the people said. Amazon has also been reaching out to people.

Among those on the short list for the position include former Medicare chief Andy Slavitt, former United States chief technology officer and Castlight Health co-founder Todd Park and ex-Aetna senior executive Gary Loveman.

Whether or not anyone in this group would take the job is another story. Slavitt recently disclosed plans to invest in health-tech start-ups via a new venture capital fund, and Park is working on a new insurance business called Devoted Health. Park told CNBC, "While I wish this new endeavor the very best, I am not a candidate to lead it." Slavitt and Loveman declined comment.

Silicon Valley venture capitalist John Doerr has taken an informal role in the search, making calls to top health executives and even making a trip out to Nebraska to Berkshire's headquarters. Doerr, who's primarily known for his technology investments, has taken a personal interest in health care in recent years, including investing his money into the sector.

Doerr is a veteran partner at Kleiner Perkins Caulfield & Byers and an early investor in Amazon. He did not immediately return a request for comment.

What the joint venture's leader would actually do to improve the health care experience for U.S. employees of the three companies is still a mystery. The group has been vague on details, except to state with the initial announcement that they hoped their size and scale would be enough.

The three companies may disintermediate the middlemen in the drug supply chain, such as the pharmacy benefits managers and drug distributors, or bring in new technology like telemedicine to improve access to primary care for workers across the country.