W. Herbert Smith is normally an Energizer Bunny. He's into everything. He knows people wherever he goes.

The longtime Cincinnati resident was a behind-the-scenes political and civil rights organizer, a federal government bureaucrat, and is now a college instructor.

For three years, he's been teaching management and marketing in China. During the height of the SARS scare, Smith was quarantined with hundreds of teachers and students for weeks in small on-campus apartments, sharing the not-always-sanitary cafeterias and communal bathrooms.

Smith didn't contract the potentially fatal, flu-like illness.

Then he came to Cincinnati in mid-July for a visit, and he got something that nearly killed him: deep-vein thrombosis, or DVT.

It started as a small blood clot behind his right knee. It grew and part of the clot broke off, traveling to an artery in his lungs.

"His clot was huge, very impressive," said Dr. Jason Lance, one of his treating physicians at Christ Hospital.

"His was so massive it was occluding (blocking) one of the major segments of the right pulmonary artery."

Smith didn't know he was sick.

When he completed the 25-hour flight from Tokyo to Chicago to Cincinnati, jet-leg hit. He slept a few days. Then came two weeks of driving to visit family and friends in the Carolinas, Georgia, Maryland and Illinois. He didn't stay anywhere long.

"I didn't want to overstay my welcome," he said from his bed in intensive care.

About a week ago, just a few days before he was to fly back to China, he noticed a hard lump behind his right knee. Later he began feeling tired, out of breath.

A friend became alarmed and rushed him to the hospital, where he underwent an operation in which doctors inserted a metal structure to catch any future breakaway clots.

If Smith had boarded the flight, it could have been "instant death," Lance said.

DVT is nicknamed the "economy-class syndrome," because many cases are associated with long airline flights. Former Vice President Dan Quayle was treated for a clot in his lungs in 1994. In April, David Bloom, an NBC TV reporter died of one while covering the war in Iraq.

The airline industry worldwide is fighting lawsuits alleging that passengers aren't being warned enough about it. Many airlines have begun suggesting on the backs of tickets that passengers stretch their legs and wear travel socks.

But there are other ways to get DVT, which Lance says is a swift and often ignored killer. Most others at risk are patients recovering from surgery, people with leg injuries, women who take birth control pills or hormone-replacement therapy, pregnant women, sufferers of inherited blood conditions or high blood pressure, smokers and obese people.

Some 2 million Americans each year get DVT, according to the National Institutes of Health; 600,000 develop pulmonary embolisms like Smith's. About 60,000 die.

"I've seen tons of (blood clots), especially in the summer," Lance said. "It's important for people who go on long trips to flex and extend their legs."

Smith, who was released Tuesday, is handling this health scare with aplomb.

"The good news is, I'm not dead," he said, "The bad news is, I'm unemployed."

E-mail damos@enquirer.com or phone 768-8395