Originally posted by Mellie at FluTrackers
wearing a N-95 mask helps reduce infection
http://www.flutrackers.com/forum/showthread.php?t=6473
A friend wrote asking for information to help convince a co-worker that wearing a N-95 mask helps reduce infection. Here's what I wrote.
For the person saying "There's no evidence that masks help... why should I wear one?..."
The person is right. There is no definitive evidence that N95 or N100 masks can be guaranteed to prevent H5N1. We say that in the Pandemic Response Plan. The reason there's no evidence is we have not had an influenza pandemic recently to compare infection and mortality rates of those who wore them with rates of those who did not. (grin) A disposable N95 or N100 mask is breathable. The disposable mask is a level of protection intended to reduce the amount of contamination, not eliminate it. (You'd need a SCBA for that.)
N-95: The N stands for Niosh approved. The number tells you filtration efficiency, about 95% in this case. N-100 has a filtration efficiency of around 98%. Neither is 100% efficient. The key is to get properly fitting masks. You should do a fit test on the mask for best results.
In one Canadian study, Canadian nurses who wore N95 masks during the SARS outbreak became infected with SARS significantly less frequently than those who did not. (Can't find the Canadian one.)
Here's another study originally published in The Lancet and done in Hong Kong -- Face masks are best protection against SARS:
http://www.newscientist.com/article.ns?id=dn3692 "Wearing a N-95 mask can give a person dealing with SARS patients in hospital up to 13 times more protection compared with not wearing one." and "Not one of the 69 staff who used all four recommended protection measures - wearing a mask, gloves, gowns and washing their hands - contracted the virus.")
Note also that the SARS virus is a Corona virus (not Influenza A virus), and is larger than the H5N1 virus. Both viruses can catch a ride on water droplets expelled in coughs, sneezes and in talking or breathing. But H5N1 viruses are so small they can also float freely in the air for a while. A person who is shedding H5N1 virus is contributing to viral load in the air. (see attached cough photo) You're more likely to become infected if breathing air high in viral load than low in viral load.
When you inhale, you draw the virus in the air toward you with a degree of "pull" that helps it penetrate through a protective material. So to be effective, the mask material needs to be tightly woven enough to filter out certain size particles. That's also why labs and hospitals where dangerous organisms are present maintain negative air pressure and have a hepa filtering process.
Masks are a big part of the protection equation. Equally important are eye barrier goggles and gloves, and something protective to cover your clothes.
Gown or jumpsuit first... A Tyvek gown or Tyvek biohazard jumpsuit is also breathable and slightly more penetrable than the N-95 mask. In my opinion and I am not a physician, if you were without tyvek suit, you could probably also get away with wearing a cheap rain suit, shower cap and boot covers. You could decontaminate the rain suit with a bleach solution and reuse -- since the suit is protecting only your skin and reducing virus on your clothing. Flu virus on skin is not so dangerous if you wash well with soap and water. Viruses landing on either kind of protective suit usually stay on the surface, reducing contamination to your clothes or skin if you remove the suit and wash properly with soap and water. The flu virus, while not much risk for intact skin, is a big problem for eyes, nose and mouth mucosa.
So you also need barrier goggles (swim goggles work) or faceplate.
You should wear gloves, maybe 2 layers of gloves to reduce the chance those floating H5N1 virus particles will get on your hands that then touch some mucous membrane in enough viral load to infect you. Check the 2 attached photos of people working with H5N1 patients or patient samples to get an idea of their PPE. H5N1 is a biohazard level 3 organism (like ebola, but more infectious than ebola).
I think if people must work and cannot distance themselves socially, they are most likely to avoid getting sick if they follow standard precautions for dealing with an infectious person:
--wear and handle their PPE properly;
--wash hands before and after EVERY contact;
--remain more than 3 feet (or further) from the infectious person and only when absolutely necessary; and
--clean all potentially contaminated surfaces regularly.
The mask is part of reducing the viral load that can get you infected. The lower the viral load in the air you breath in or the air that otherwise touches your mucosa and conjunctiva, the better. Definitive study or no study, I plan to wear a N-95 mask or N-100 mask if/when the time comes that I need it. I'm gonna wear the other gear too and practice how to put it on and take it off safely.
Here's what CDC says
http://www.cdc.gov/flu/professionals...skguidance.htm
[snip] ... PS If those infected could wear surgical masks (without respirator in them), it would restrict the virus in the air too, which would protect others breathing the same air.
sameo416:
Fla_Medic @ Avian Flu Diary