With health-care insurers like Coventry Health Care (NYSE:CVH) coveting their high growth rates of the past few years, it's no wonder they'd want to seek out untapped regions with the potential to fuel further expansion.

And when it comes to growth, you can't do much better than China. Heck, its Commerce Department describes the country as the "world's largest untapped insurance market." It's hardly surprising that U.S. insurers are hungry for a piece of the action.

Clearly, a lot of the growth will come from China's booming middle class, but there's more to the market than just the increasing number of people who can afford coverage. Expatriates at multinational companies that have expanded into China are also demanding the same sort of health insurance they have back home. Health insurers probably don't have to maintain a base in China to sell health insurance to multinational companies, but it certainly should help those potential corporate clients determine health-care costs.

It's going to be a while
Aetna (NYSE:AET) recently joined WellPoint (NYSE:WLP) and UnitedHealth Group (NYSE:UNH) in setting up shop in the top gold-medal winning country. Cigna (NYSE:CI) has been there since 2003, and it's reportedly already turning a profit.

Since China requires that a foreign company be set up for two years before it enters the market, investors in companies that have recently established offices in China will have to wait a bit before they start seeing revenues denominated in renminbi. Most companies use that time to do research and to find a local partner -- another requirement for foreign companies.

More than just health insurance
Much like they've done stateside, health insurers' offerings will likely be wider-ranging than mere individual and group health plans. Some companies plan to get into health administration, risk management, and care coordination -- helping other insurers save money. The companies are essentially taking what they've learned in the U.S. and applying it to a growing field of Chinese medicine. Getting to start from scratch could result in efficiencies that managers stateside only dream about.

Most Chinese workers rely on government-run programs to cover their health-care costs, but there are often gaps in coverage that can cost a fortune for individuals with unforeseen medical issues. To fill the gap, Cigna offers hospital indemnity insurance that pays for hospital expenses not covered by the state-run system.

Some companies are also planning to offer life insurance policies. That's not a huge stretch, considering that some companies such as Humana (NYSE:HUM) have bought smaller Chinese insurers offering similar ancillary products recently. Partnering will be highly important if insurers move into this area, since they'll have to compete against resident experts like China Life Insurance (NYSE:LFC); that could be difficult, given the cultural and governmental differences.

Worth keeping an eye on
At this point, it doesn't seem that China is contributing materially to any of the health insurers' bottom lines. Still, investors should still keep an eye on this growing market. Cigna is clearly one of the early movers, which should help it grab market share, but I'd guess that U.S. firms' choice of Chinese partners will play an equally important role in establishing the eventual market leader.

Fortunately for investors, this battle is likely to play out over years, not weeks or months. That should give investors plenty of time to do their homework and try to figure out which company will come out on top.

More Foolishness on the Olympic host country:

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. WellPoint and UnitedHealth Group are Motley Fool Inside Value selections. UnitedHealth Group and Coventry Health Care are Motley Fool Stock Advisor recommendations. Try any of our Foolish newsletters today, free for 30 days. The Fool's disclosure policy is like an insurance policy for you.