I was watching a Nova episode about Ebola. A scientist mentioned how extremely dangerous it is when a part of the suit rips as described in my thread title question. This got me thinking about all the tv shows and movies I’ve seen (fictional and non-fictional) in which the suit rips, the scientists look at each other in horror, the poor person with the suit leaves & then takes a bunch of precautions - showers, UV light, medical treatment, etc. - and then DIES. EVERY TIME. I get that it makes for good drama. And I was wondering if maybe the lab conditions make for dealing with concentrated substances & microbes or super-engineered bugs.
But I was wondering what the statistics were on on this. I tried googling and checking cdc but could not find anything definitive. All I found were numbers on the total number of laboratory-associated infections as here: http://www.cdc.gov/biosafety/publications/bmbl5/bmbl5_sect_i.pdf
Wikipedia has a page on “Positive pressure personnel suits” used in among other things BSL-4 labs. The term “positive pressure” refers to the fact that they are kept pressurized so if there’s a tear air will flow out of the tear instead of into the suit.
No statistics, but the whole point of pressurizing it like that is to prevent the “suit rips, die every time” scenario.
I work in a BL3 lab, rather than a BL4, but if working in an actual BL4 lab, rather than in the field, the risk would be quite low. Labs rated BL3 or 4 have one-directional air flow and all manipulations of infectious materials are only done using a biosafety cabinet which has an independent one-directional air-flow. As an additional precaution, personal protective equipment is layered. For example, my first layering consists of a pair of disposable socks, croc shoes, plastic booties, scrubs, bouffant cap, and gloves, all of which are put on in one room. Moving to the next room, I put on tyvek boots, a tyvek suit, a respirator, safety glasses, a tyvek head-covering, and a second pair of gloves. In the next room, I put on a tyvek wrap-around gown, and then I can actually enter the lab. Before I exit the lab, I remove my outer pair of gloves, and put on a fresh pair and spray my tyvek wrap and boots with 20% bleach. I then go to the next room, remove my outer wrap and tyvek boots and change my outer gloves yet again. I also spray my tyvek suit and my feet with 20% bleach. In the next room, I remove my outer pair of gloves, my tyvek head-covering and the tyvek suit and booties. In the next room, I remove everything left, take a shower, and put my own clothes back on. In a BL4 lab, the main difference would be that rather than a respirator that filters the air, I would be wearing one that comes with its own air supply, and that instead of a tyvek wrap for my outer layer, I’d wear another full suit over the first. If aersolization outside of a biosafety cabinet was a possibility, I would also wear a pressurized suit over the tyveks.
The real danger in a BL4 environment is if someone is working in the field. The environmental controls aren’t in place in the field; rather than having aerosolized infectious agents removed by the air-flow, they recirculate, increasing the risk of exposure if one’s personal protective equipment is compromised.
Amberlei, I’ve read in some novels concerning Ebola that in addition to scrubbing down with bleach solutions, somewhere along the “disrobing” line there’s exposure to UV lights. Is this true?
Remember that Ebola is not transmitted through the air, which reduces any risk from a torn suit. The Spanish nurse thinks she got it from inadvertently touching her face while removing her suit, by contrast.
many safety precautions in extreme hazard situations (medical, biological, chemical, electrical, non-life sustaining environments, …) you really have to have your wits about you.
every second you need to think, ‘this is not normal world’.
On a related note, is it true that if you prick your finger with a pathogen-contaminated implement or get bitten by an infected animal, protocol is to amputate your finger immediately?
There have been four cases of lab workers exposed to ebola due to a needle stick injury. In none of these cases was the patient subject to an amputation.
If virus particles may have entered the bloodstream they could be carried far away from the exposure site long before you could amputate a finger, even by crude means.
If you mean how long it takes for a finger stick to be circulated around the body …
IANA medical anybody, but for round numbers your heart pumps the entire volume of your blood every 90 seconds. That’s if you’re at rest; if you’re exercising it’s about half that or 45 seconds. So any pollutant which got directly into a blood vessel would be pretty thoroughly distributed throughout your body in at most a few minutes.
I’m going to speculate that some pollutant injected just a bit into fat or skin or muscle which missed a significant vessel would diffuse a bit slower into the capillaries. But once it worked it’s way into a vessel, at least some of the sample is gonna be everywhere in the body almost immediately. If you poke yourself anywhere with a pin, blood emerges within a couple seconds; clearly the capillary beds are dense enough to give quick communication from the blood stream to any point on your surface. I have to assume communication speed the other way is broadly similar.
I think this is referring to how long it takes for the entry/exit procedures for a BSL3/BSL 4 lab. This virology blog provides descriptions of procedures at some other labs.
In that case, exit required four minutes plus time to change clothes - call it six to eight minutes total. Entry is generally quicker as there are not decontamination showers.
In the above reference article the author mentions the AAHL has Multiple waste cook tanks. Another smaller lab, NEIDL (National Emerging Infectious Diseases Laboratories in Boston), has three large 5600 liter collection tanks in the mechanical space. The cook tanks are used to autoclave waste. Having multiple tanks allows a lab to have one accumulating incoming waste while another is used as an autoclave to sterilize the liquid wastes. Additional tanks can be used for reserve capacity.
As for the air… the labs are kept in negative pressure. In the case of the AAHL (which is a particularly large lab) there is a stack of 1000 HEPA filters that the outgoing air must pass through. Though the article does not mention it, UV and/or heat treatment may be used at some labs before air exhaust is mixed with the outside air.
I don’t know about this particular question, but I will say that in general, UV needs to be really REALLY strong to be any use at all as a disinfectant. I used to work in a DNA lab with dead air boxes with built-in UV lights. Every night we’d turn on the UV lights to “disinfect” the boxes. One day, someone got curious and put a sensor in the box to see just how strong the light was. It turned out to be ridiculously weak, such that you’d need to shine it for several days straight before it would have a chance to kill even a single microbe. Similarly, there are water treatment facilities that pass the water through UV light to sterilize it. Unfortunately, it turns out that even strong UV can only penetrate something like a half-inch of water.
I guess what I’m saying is that although UV is often used as a disinfectant, in my experience, it’s more of a placebo than actually effective. I would hope, however, that the people designing BSL 3 and 4 labs are a bit more clever than that.
No one’s asked the guy if he needed answer fast.
About amputation immediately following needlestick, I know I’ve read some cases where AIDS workers have considered this, and (unverified by me) done this. A doctor decided not to amputate his arm and contracted AIDS–that was definitely in the mainstream news within the last year or two.
In discussing the U.S. Ebola virus case(s?) with my family, one thing I often say is that “Ebola is not magic”. That is, it has concrete physical limitations governing how it can spread.
Given that, I am wondering if the nurse in question meant she touched the skin on her face (say, her cheek) or if she touched “her eyes/inside her nose/inside her mouth”? Can any human pathogen infect a person by ONLY contacting intact, non-mucous skin? Through sweat glands or something?
Hard to blame him. I think amputating an arm would cause almost as much inconvenience to life as having AIDS - especially considering it wasn’t guaranteed he was going to get AIDS. Amputating a finger, perhaps yes, but an arm, no.
It only takes about 8 minutes, though can take longer depending on the respirator you use. I use a disposable one, but people with facial hair or asthma use a PAPR respirator that covers the whole face and delivers filtered air automatically. These come with filters that need replaced every so often and before putting one on, you need to do a filter test and a battery test and that process takes about five minutes on its own. I would think that if someone is needing to carry their own air to breathe, they’d have a similar testing process also.
Reversing the process takes a bit longer, because you’ve got to be so cautious when removing an outer garment that you don’t touch an inner garment, and then the whole showering process afterwards takes a bit of time.
My pathogen is resistant to UV light, but our BL3 lab suite is set up so that you can remotely regulate UV lights to decontaminate a room for agents that are susceptible to UV irradiation. We also have UV lights in the biosafety cabinets, but even our biosafety officer said that those are useless. I doubt that people working with ebola are subjected to UV light as the intensity would probably be so high that frequent exposure would result in melanoma. This is just a guess on my part, though. I know ebola is highly susceptible to UV irradiation so perhaps even a very low intensity would kill it?
While ebola is not spread through inhalation, there is the risk that aerosolization could spread the virus to other surfaces, not that this would pose a risk even if the suit was torn, due to the airflow out of the suit. Ebola doesn’t live long on fomites, but every surface should be treated as if it’s a potential source of exposure. When you’re wearing a respirator, goggles, and several layers of clothing, you get hot and sweaty, really, really hot and sweaty. I am guessing that if she touched her face while removing her suit, the virus was transported to her eyes or mouth by her perspiration.
Our lab suite has a series of HEPA filters that filter the air before it’s released to the environment. We have a reservoir that captures water from the showers and sinks and everything is chlorinated before release. Waste waters are also subjected to UV irradiation as they travel through the pipes to the reservoir, but our organism is resistant to UV. All of our other wastes get autoclaved and then sent to a biomedical waste facility where they’re incinerated. Once a year, or when needed to remove a piece of equipment or to decontaminate after a spill, the lab undergoes sterilization with vaporized hydrogen peroxide. At this time, the HEPA filters are replaced, biosafety cabinets are recertified, and an inventory of all of the equipment is done. Walls are also repainted at this time. The decontamination process takes three days and replacing all of the filters and doing everything else takes about three weeks. Our most recent decontamination was done to remove a -80 freezer that broke down. The really horrible thing about that is that it occurred just a couple of weeks after we’d been able to reopen the labs after the annual decontamination.
I don’t think this would do a lot of good, because it would take just seconds after infection before the organism entered your bloodstream. What we’re advised to do is to immediately milk the wound and to keep milking it at least 15 minutes. This reduces some of the risk, as you’re trying to reverse the flow of blood; instead of recirculating, the blood gets expelled. I don’t know how well this actually works and hopefully never will have cause to find out. We work on a buddy system, so that nobody is ever, under any circumstances, alone in the lab. If you’re stuck, while you’re milking the wound, your buddy is supposed to call our biosafety office and they’ll send someone to assist. Someone who shares our lab suite recently got stuck with a needle that had been used to infect a mouse with TB. She had to get a TB test and will be getting one each month for the next few months.
