Word of mouth marketing has seen an explosion in the Internet age. YouTube videos from complete unknowns can reach hundreds of millions of viewers around the world in a chain reaction that starts with one person passing it along to another.

Well, Meteor Solutions says it can map that chain reaction. The Seattle-based company provides a way to track fast-moving data — such as an email or a video — as it gets passed along. It lets advertisers and publishers track the spread of their messages or content (much like the Centers for Disease Control tracks the spread of an infection) and gives them options to advertise or otherwise spur the virus so that it spreads even further.

Meteor Solutions, which was born out of a merger between Reach Machines and Fyreball in August of last year, packages its analytics technology with a monthly subscription fee starting at $295. (Fees vary, based on traffic).

A patent-pending Meteor Tracker tool places “tracking scripts” in the form of Java code into media to monitor how it spreads from user to user or web site to web site or from instant messenger client to client. It’s like slapping an identifying code at the end of a web link.

As the tracked content spreads, Meteor Tracker generates a sharing graph that identifies each node (a unique visitor, stripped of identifying private information) and captures every single visit to a site that is generated by a user who sees the tracked content. If a site wants to convert users to an action, such as buying a subscription, Meteor Tracker will track that, too.

Another tool, Meteor Ignite, gives advertisers and publishers widgets for accelerating content sharing by allowing visitors to a site to, say, share content quickly via social sites like Digg, Delicious or Facebook. That’s for free. For an additional fee, Meteor Ignite has premium promotion and content-sharing features for those who want to add more juice to their campaigns.

The big problem with word-of-mouth marketing is that it’s hit or miss. Who would have thought that a video someone putting Mentos candy inside a bottle of Diet Coke would be seen by more than eight million people on YouTube? Meteor’s top executives, Ben Straley and Pete Parsons, say they can capture the relevant data that explains how, why and where word-of-mouth spreads, making free media as easy to measure as paid media.

“In a bad economy, you want your ads to get results,” Straley said.

Fyreball, founded in early 2007, had part of the answer. Its chief executive was Parsons (chief of products for Meteor), the former head of the Bungie game studio that created the Halo series of games for Microsoft. Fyreball was a social network with tools that made it easy to pass along games, videos, pictures and emails to friends. With its Meteor Tracker technology, Fyreball could track the spread of the viral media, but it was primarily targeted at consumers and had a tough competitor in ordinary email. Parsons said that the company wasn’t able to create a sustainable business with Fyreball alone. Fyreball itself is on hiatus.

Reach Machines, founded 2.5 years ago, was focused more on getting businesses to adopt word-of-mouth and target it to the right customers based on relevance and their willingness to purchase something. By combining, the companies are now focused on making tools for marketing experts at advertisers and publishers. They let the customers measure and buy against online-word-of-mouth as it happens, says Straley. The data is updated every six to 12 hours.

Competitors include Constant Contact and Site Analytics.

Customers include Creature, Ayzenberg, Microsoft, Questus, and the game developers Smith Tinker, Bungie and Bethesda Softworks. The company has six employees and is funded by angels. On average, web sites currently running Meteor tracking software have found that they receive 20 percent of their total unique visitors through online content sharing in email, and IM, as well as on social sites like blogs, Facebook and Twitter.