Keeping Cool in the Hot Zone

Every precaution is taken to safeguard researchers who work with the world's deadliest viruses.

Dr. Mike Holbrook, director of the Robert E. Shope, M.D., Laboratory, a Biosafety Level-4 lab at the University of Texas Medical Branch at Galveston, deals with some of the deadliest viruses known to man, including Ebola, Marburg, Lassa, Junin, and Nipah viruses. It goes without saying that special precautions are put into place to ensure total security and safety.

Before entering a BSL-4 lab, entrants must pass through a security checkpoint that verifies they have all the proper credentials. Once they’re inside the facility, the security screening has just begun. “Our building has many different levels of security access stuff on the way in,” Holbrook said. “All the floors are security access, all the elevators, and so forth.”

Upon arriving at the BSL-4 lab, researchers must first enter a “Clean Change Room” in which they change out of their street clothes and put on scrubs. From there they enter the suit room to don a positive-pressure suit. “You’ve probably seen them on TV or on the Web; they’re big, blue suits that we have medical-grade breathing air pumped into them,” Holbrook said.

When researchers are in the lab, one of the first things they do at their stations is connect to the air supply. The positive pressure provides added safety for the researcher, pushing air out in the event of a tear or puncture in the suit, but the suit’s air pressure is not without its risks. Holbrook said there is a chance of dehydration.

“You figure, if you’re running 14 pounds of air through your suit continuously for four or five hours, you can get dehydrated pretty fast. So that’s one of those things that we have to be very careful about and pay attention to,” he said.

Minimizing Puncture Hazards
Working with animals poses puncture risks. “In that environment, you’re working with something that bites, and especially if they’re sick, they’re not very happy. When working with animals, we anesthetize them before we do anything,” Holbrook said.

Handling sharp objects, such as needles, has its own hazards. To minimize these risks, no researchers use scalpels or knives, and all scissors are blunted on one end. In addition, before gaining access to the lab, researchers must first go through a special training program taught in a mock lab so they can get used to moving around and working in their suits. “It’s a new environment, and it gives them a chance to get used to it before they get into the hot zone,” said Holbrook. Only after researchers have demonstrated a significant aptitude for successfully working in lower-level containment labs, such as BSL-3, may they start training for BSL-4, he said.

Clearing the Air
The suits are considered a last line of defense behind several other safety tools to prevent viral exposures. Enclosed biosafety cabinets employ an inwarddirected and HEPA-filtered air system to prevent microbes from escaping. “People ask, ‘Would you ever be worried about not having your suit on in the lab?’ My answer is no, because when people are working properly everything is in the cabinet. The cabinet is doing its job. The air in there is clean,” he said.

If something were to be released outside a biosafety cabinet—for example, if someone dropped a virus culture on the floor—Holbrook says it would be sucked into the laboratory’s air filtration system, which cycles through 15 to 20 complete room air changes per hour. In this process, air is screened through a double-HEPA filtration system before being exhausted. The air flow between these filters is continually monitored by computer sensors that alarm if the air flow through them drops for any reason.

If a virus were to make it through these safeguards and exit out of the building’s stack, Holbrook said it wouldn’t get far. “With all the viruses we work with in BSL-4, none of them like the sun very much, and none do very well when they get dehydrated,” he said. “Even in our nice humid environment down here in Galveston, if a virus particle was shot out the top of our chimneys, it would survive maybe six inches.”

Decon at Shift’s End
At the end of a work shift, researchers exiting the BSL-4 lab go through an eight-minute decontaminating shower, which rinses the suit with chemicals and water, before the suit may be removed. From there, the researchers must take a hot shower before donning their street clothes and leaving.

The Robert E. Shope, M.D., Laboratory is the only full-sized BSL-4 lab on a university campus in the United States. The Galveston National Laboratory, UTMB’s second BSL-4 lab, is scheduled for completion in June 2008.

This article originally appeared in the February 2008 issue of Occupational Health & Safety.

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