Non-Pharmaceutical Interventions – Part II
Posted by preparedcitizens on January 20, 2008
This is an update from the original post 12-14-2007 here
A report from the Council of Canadian Academies entitled:
There is an interesting discussion that I want to attempt to highlight.
The discussion is that there are 2 major modes of influenza transmission. Inhalation transmission and Contact transmission being those two modes.
The
“influenza virus exits the respiratory tract of an infected person: (i) expulsion of the virus into the air through sneezing, coughing, speaking, breathing or through aerosol-generating medical procedures, or (ii) by direct transfer of respiratory secretions to another person or surface. The new host acquires the virus either by inhalation of the infectious particles from the air or by contact with infectious material directly or via self-inoculation through a contaminated hand.”
This is where the two primary transmission modes, inhalation and contact, come into the picture.
In inhalation transmission there are ballistic particles and inhalable particles. Ballistic particles are more effected by gravity and have an infectious range of under 3 feet with a particle size of 100 μm¹. These particles may remain in the air from seconds to days. These particles are deposited on the mucous membranes (eyelids, lips and nostrils, etc.) and not inhaled.
“The inhalable particles can be classified into three size categories that have different deposition behaviour. Nasopharyngeal-sized particles range from approximately 20 to 100 μm in diametre and tend to travel no further than the upper respiratory tract. Tracheobronchial-sized particles have a diametre ranging approximately from 10 to 20 μm and are capable of depositing as far down as the tracheobronchial region. Alveolar-sized particles are less than approximately 10 μm in diametre. They are the only particles capable of reaching the alveolar region but can be deposited anywhere in the respiratory tract.”
The article goes on to state that there is evidence that the recommendation from the CDC described as the “three-foot-rule” is now practiced to be at around seven feet. There is thought that even long range inhalation transmission of influenza viruses is possible, how long that distance is is not clear to me but the article states that there is evidence that influenza is transmitted primarily at short range.
Contact transmission relies on transfer of the virus through direct contact with an infected individual through kissing or by touching a contaminated surface.
“The panel concluded that No evidence has been found that hand hygiene or other interventions that might prevent contact transmission (e.g., glove use in healthcare facilities) prevent the transmission of influenza.”
So, off with the gloves? Not necessarily. The last line of defense may be the only line of defense that the average citizen has.
In the absence of vaccines and antivirals the measures that we can take are temperature and humidity control (warm, humid environments inhibit viruses), quarantine and isolation methods, hand hygiene, respiratory etiquette, school closures and discouraging public gatherings.
The recommendation from the article:
Personal protective equipment (PPE) — e.g., goggles, gloves, gowns, surgical masks and respirators — is considered the “last line of defense” against exposure and supplements engineering and administrative controls. Personal protective respiratory equipment (PPRE) is a sub-category of PPE designed to block inhalation of hazardous airborne contaminants.
One point that is brought up in this article is the proper use and disposal of personal protective equipment. Masks must be fitted on the face correctly or they will not be useful.
From the CDC site:
Wearing a Facemask or a Respirator
Very little is known about the benefits of wearing facemasks and respirators to help control the spread of pandemic flu. In the absence of clear science, the steps below offer a “best estimate” to help guide decisions. They will be revised as new information becomes available.Consider wearing a facemask if:
• You are sick with the flu and think you might have close contact with other people.
• You live with someone who has the flu (you therefore might be in the early stages of infection) and need to be in a crowded place. Limit the amount of time you spend in these crowded places and wear a facemask while you are there.
• You are well and do not expect to be in close contact with a sick person but need to be in a crowded place. Limit the amount of time you spend in these crowded places and wear a facemask while you are there.
Consider wearing a respirator if:
• You are well and you expect to be in close contact with people who are known or thought to be sick with pandemic flu. Limit the amount of time you are in close contact with these people and wear a respirator during this time. These recommendations apply if you must take care of a sick person at home.
Surgical masks on the patient and careful respirator use of the caregiver may have some benefit.
What is a facemask?
Facemasks are loose-fitting, disposable masks that cover the nose and mouth. These include products labeled as surgical, dental, medical procedure, isolation, and laser masks.
Facemasks help stop droplets from being spread by the person wearing them. They also keep splashes or sprays from reaching the mouth and nose of the person wearing the facemask. They are not designed to protect you against breathing in very small particles. Facemasks should be used once and then thrown away in the trash.
What is a respirator?
A respirator (for example, an N95 or higher filtering facepiece respirator) is designed to protect you from breathing in very small particles, which might contain viruses. These types of respirators fit tightly to the face so that most air is inhaled through the filter material. To work the best way, N95 respirators must be specially fitted for each person who wears one (this is called “fit-testing” and is usually done in a workplace where respirators are used). Most of the time, N95 respirators are used in construction and other jobs that involve dust and small particles. Some healthcare workers, such as nurses and doctors, use these types of respirators when taking care of patients with diseases that can be spread through the air.If you have a heart or lung disease or other health condition, you may have trouble breathing through respirators and you should talk with your doctor before using a respirator.
From the Minnesota Department of Health:
Like surgical masks, N95 respirators should be worn only once and then thrown away in the trash.
To PPE or not to PPE, that is the question only you can answer for yourself.
