One of the fastest-growing areas of healthcare is telemedicine, or the remote diagnosis and treatment of patients using a video or a phone conversation. Adoption of this low-cost, on-demand approach is already driving revenue higher at Teladoc (NYSE:TDOC), a publicly traded telemedicine provider, but it's also been a boon for American Well and MDLive, two private telemedicine companies that are tapping investors for big money to fuel their growth. Main Street investors can't buy stock in them yet, but the possibility of them going public someday makes them worth watching.

In this clip from Industry Focus: Healthcare, host Shannon Jones is joined by Motley Fool contributor Todd Campbell to explain why Cigna (NYSE:CI) has taken an equity stake in MDLive and Anthem (NYSE:ANTM) has invested in American Well.

A full transcript follows the video.

This video was recorded on Nov. 14, 2018.

Shannon Jones: Todd, with the time we have left, let's switch gears just a bit and talk about two privately held companies, the first of which is a company called MDLIVE. It started back in 2006. It sounds very similar, to me, to Teladoc. But, it's attracted the likes of some big-name healthcare backers and partners.

Todd Campbell: What's interesting for investors to keep an eye on, I mentioned early on when we were talking about Teladoc that of the big three, Teladoc is the only one that's publicly traded. Two more, these other two that you should be keeping your eye on. MDLIVE is one of them. They have about 30 million consumers that are enrolled as members because of relationships that they have with different healthcare payers. They expect to do about 500,000 virtual visits, that's the run rate right now, per year. Smaller. That's less than what Teladoc did last quarter. Still, a big player.

And, as you mentioned, big investors in the healthcare area, especially as of this year, through a new capital raise that they did, include Cigna, which is a major insurer, and Novo Holdings, which is the venture capital arm of Novo Nordisk, a major biopharma company.

Jones: The other company is actually the company that's been behind Apple's health study, a company called American Well. For those of our listeners who aren't familiar with the Apple heart study, Apple has been using an app using the Apple Watch -- wearable devices -- to identify irregular heart rhythms, including those from potentially serious heart conditions like atrial fibrillation. The Apple heart study is basically utilizing this video consultation to connect participants in the study to physicians 24 hours a day, seven days a week. Let's talk a little bit more about American Well, one that I didn't even realize was a part of this study. It's gotten so much press. I didn't realize just how connected they were to Apple.

Campbell: This another company that you can't buy yourself, necessarily, unless you're one of the lucky few. It's a private equity, private venture. But they're raising a truckload of money -- just shows how much interest there is out there in telemedicine companies. They just raised $366 million this summer alone. Participating in that capital raise was Philips, which is one of the global leaders in telemedicine technology. They're actually going to be joining American Well's board. Anthem Health is also an investor in this company. One of the things that's interesting when you look at MDLIVE and American Well is to see that these insurance companies are taking these equity stakes within these telemedicine providers. I think that's incredibly encouraging for what their view is of telemedicine in the future, and how it could change how people get low-cost care.

Jones: Absolutely. Definitely a positive there. In closing, Todd, it sounds like telemedicine, intriguing opportunity for investors if you're not already in the space. An even more intriguing value proposition for patients. Everyone can agree that healthcare costs here in the U.S. are out of control and need to be reined in. Sounds like telemedicine could be just what the doctor ordered to help with that, Todd.

Campbell: Absolutely. And like most things, don't go crazy with it in your portfolio. But keep an eye on it. I think it's really exciting. In ten years from now, these companies are going to be a lot bigger than they are today.