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Every day, deadly germs are shipped across the country and around the globe, right alongside the books, gourmet foods and birthday presents sent through FedEx Corp. (search) and similar couriers.

Often their journeys can be circuitous, too.

Follow, for instance, a single vial of the potentially deadly flu virus causing a world health scare because it was included in test kits sent to more than 4,000 laboratories. It was grown in a Virginia lab, spent time in a Cincinnati freezer and passed through a small medical company on the Mexican border before it finally arrived at a Milwaukee lab.

Health experts, government officials and the couriers insist the transportation of these germs is tightly regulated, and that the samples are heavily packaged and labeled to ensure safety. A catastrophic outbreak has never occurred as a result of such shipments.

"The safety level of the transport of biological material is incredibly high," said Dr. Jared Schwartz, a microbiologist and officer with the College of American Pathologists (search), which is in charge of the flu testing program. "I have no concerns about the safety of the transport."

But accidents do occur — and some scientists feel they've been too close for comfort.

Last month, a FedEx truck carrying five boxes of samples of anthrax, flu, tuberculosis, salmonella and E. coli (search) collided with a car in Winnipeg. None of the dangerous germs escaped.

In 2003, a FedEx package containing West Nile virus exploded at the Port Columbus International Airport in Ohio. Firefighters suspected dry ice caused it to burst open. No one was injured, but 50 workers had to be evacuated.

"This has been a big concern for us," said Sujatha Byravan of the Council for Responsible Genetics, a Boston nonprofit fighting the U.S. expansion of high-containment labs that will be home to the world's deadliest germs.

At least 18 such "hot labs" are being planned or built in the United States in the coming years, and a growing number of scientists are being trained in the darker aspects of microbiology as part of a huge federal effort to combat bioterrorism.

"The more FedEx exchanges of biological material you have between labs, the more opportunities there are for accidents," Byravan said.

The thousands of deadly flu samples that labs were hastily destroying at the urging of global health officials originated at American Type Culture Collection, according to the college of pathologists. ATCC is a nonprofit laboratory in Manassas, Va., that ships many of the nation's flu viruses and other dangerous germs to labs everywhere.

ATCC was created in 1925 by a group of scientists who wanted a central location for the nation's supply of germs for laboratory use. The organization's biological library has grown to 100,000 different specimens. It ships 150,000 biological items annually, making revenues of $32 million, according to its latest publicly available tax return.

An ATCC spokeswoman declined comment for this story.

In the days since some concerned Canadian scientists alerted the World Health Organization that their test kit included a flu strain responsible for killing between 1 million and 4 million people in 1957, blame is being placed on Meridian Bioscience Inc. of Cincinnati for shipping thousands of vials of the dangerous bug around the world.

In 2001, the Food and Drug Administration warned Meridian that the monitoring and tracking of components of its test kits failed to meet federal requirements. The problems led to a recall of 30 products and employee layoffs.

As it turns out, most of the Cincinnati company's test kits with the 1957 bug were ultimately assembled and shipped via FedEx and DHL by Proficiency Testing Service, a tiny Meridian subcontractor in Brownsville, Texas.

The test kits are sent three times a year to labs needing to certify their competency at identifying flu viruses. These kits included five samples. This time, one vial in each kit contained the dangerous 1957 flu strain.

The Milwaukee Health Department got its test kit from Brownsville on Feb. 23, said Gerald Sedmak, the city's virology chief. He said each test kit costs the city about $600.

Sedmak said the public health threat was low because the flu strain arrived freeze-dried as a powder and doesn't become dangerous until water is added. What's more, Sedmak said the shipments are extensively packaged: Each vial is wrapped in a plastic bag containing absorbent material. The vials are enclosed in a hard plastic tubes, which are bubble-wrapped and packed in two heavy cardboard boxes.

FedEx said its employees and customers are "rigorously trained" to handle dangerous biological material and federal laws and company policy mandate packages be clearly labeled and properly packaged.

"The packages are handled differently ... we have to protect our employees, too," said FedEx spokeswoman Lourdes Pena. Asked for more details, she conceded that dangerous biological material is shipped right alongside any other packages — only more carefully.

Shares of Meridian fell Thursday, declining 21 cents, or 1.39 percent, to $14.91 on the Nasdaq Stock Market. The stock has been trading at a 52-week range of $9.55 to $20.56.