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Respiratory Viruses and SARS on the Wing

  
  
  
  
  

While winter is on the wane, our viruses of winter are still not finished with us yet. With a few more months of the cold and flu season left, SARS (Severe Acute Respiratory Syndrome) is trying to rear its all too ugly head. As the CDC pointed out in the video attached to the blog of a few weeks ago, besides norovirus, wintertime brings a host of respiratory infections including Influenza, respiratory syncytial virus (RSV), rhinovirus, and viruses responsible for viral pneumonia. 

 

Coronaviruses in Viral Pneumonia and SARS

 

Respiratory Viruses and SARS on the WingOf winter visitors (all of which spill into spring) respiratory viruses are responsible for approximately a third of all adult cases of pneumonia and 15% of childhood infections reported.  These are classed as viral pneumonias with the most commonly implicated viruses being: rhinovirus, coronaviruses, influenza virus, RSV, adenovirus, human parainfluenza virus (hPIV) and the recently identified human metapneumovirus (hMPV).

 

Besides the coronavirus types causing common colds, we are seeing headlines from the UK for the 12th case of SARS caused by another virus in the group. Six of the 12 cases seen globally (8 in the Middle East & 4 in the UK) have been fatal (50% mortality) and is all too reminiscent of the 2002 SARS outbreak, that infected some 8000 and claimed around 800 lives.  The WHO is referring to this as a novel coronavirus or NCoV and while concerned, public health authorities are not seeing sustained transmissions but recommend testing and investigation for the virus if any unexplained pneumonia cases or clusters of severe acute respiratory infections are experienced regardless of where they occur.  Britain's Health Protection Agency has said while it appears the virus can spread from person to person, "the risk of infection in contacts in most circumstances is still considered to be low."

 

Understanding Winter Viral Infections

 

Why winter?  Well first off, viruses like our DNA and protein containing foods such as fruit, vegetables, meat, fish and eggs survive better refrigerated.  Indeed these cold dry conditions increase survival times for all viruses across the board but there are also other factors favoring transmission.  

 

In addition, cold dry conditions pull moisture out of aerosolized droplets released by coughs and sneezes, resulting in respiratory viruses (and norovirus) able to float in the air for longer periods during the winter. 

 

These same conditions also tend to dry out the nasal passages with negative consequences making virus transmission more successful.  It seems the mucous membrane in our noses serve as a primary defense with mucous being a rich source of antibodies and natural antimicrobial molecules.  In addition damaged mucosal cells, permit easier entry of upper respiratory viruses such as those causing the common cold and flu, into the body. 

 

Cold winter climates cause large numbers of people to stay indoors in more habitable temperature controlled environments. This means people are crowded into highly populated places where opportunities for transmission of infectious pathogens is increased via sneezing and coughing and contaminated surfaces.

And finally, if all of the above were not enough, all of our respiratory viruses of winter are easily inactivated by sunlight, in short supply in winter months.

 

What Makes these Respiratory Viruses Tick

 

There is a great deal of commonality with all of these viral infections of winter.  All of these viral infections are spread by:

 

  1. Direct contact with an infected person,
  2. Indirect contact such as touching a contaminated surface, and/or
  3. Exposure to an infected person who may be coughing or sneezing.

 

Sneezing is an efficient method for dispersal, as a single sneeze can cause an expulsion of air traveling at initial velocities of over 200 miles per hour containing up to 100,000 droplets and 10 million virus particles. These droplets can end up in other people's mouths or noses, where they can cause infection. The droplets can also land on objects that people touch, utilize hand transfer from contaminated surfaces to eyes, nose or mouth providing access to mucous mambranes where they spread along the respiratory tract epithelium, mostly by cell to cell transfer. A recent discovery regarding the NCoV causing SARS-like infections is that it spreads more quickly between cells reaching its peak ability to replicate in 2 days instead of 4 days with SARS virus. 

 

Survival in the Environment

 

CDC and other sources state that "80% of all infections are transmitted by hands, this includes all of the viruses of this group.  All but rhinovirus and adenovirus posses lipid envelopes resulting in poor survival on hands but lasting long periods in the environment.  RSV can persist for several hours on toys or other objects, which explains the high rate of nosocomial RSV infections, particularly in pediatric wards with up to 50% of the personnel in wards becoming infected during an outbreak.  Viruses having lipid envelopes are easily inactivated by soap and water and alcohol sanitizer. Rhinovirus is the best survivor in this group and because of this, the majority of colds are transmitted by autoinoculation by contact with contaminated surfaces and then by touching eyes, nose or mouth.

 

Effective Hand Hygiene Measures

 

Hand HygieneWe are all capable of overcoming these pathogens using simple standard, contact, and airborne precautions including hand hygiene and surface disinfection.  For influenza, respiratory syncytial virus (RSV), human parainfluenza virus, coronaviruses, metapneumovirus, adenovirus and rhinovirus, hand hygiene consisting of careful and frequent hand washing with  soap and water is the first step to limit the spread and prevent infections.  

 

If hands are not soiled, as a supplement to hand washing, alcoholic and chemical sanitizers are highly effective against enveloped viruses that act on the RNA core but first by disrupting the envelope.  With rhinoviruses and adenoviruses, alcohol sanitizer while not quite as effective, still provide high kill rates (< 3 Log 10 reduction) when used to compliment hand washing.

 

About Barry Michaels

 

Barry Michaels newBarry Michaels has over 30 years experience in the field of infectious disease investigation, control and prevention. His research work has involved a wide variety of viral, bacterial and fungal pathogens focused on antimicrobial intervention strategies.

 

Previously having worked as staff microbiologist for Georgia-Pacific Corp for over 14 years, he is now founder and director of B. Michaels Group Inc. a consultant group active in areas of product safety, product development, regulatory affairs and microbiology related to personal hygiene, surface sanitation and glove use in food, healthcare and various other occupational fields.

 

Considered the "Guru of Hand Washing" he has been cited widely in the popular press as well as published or participated in hundreds articles, abstracts, book chapters, presentations and forums on the subjects of skin care and infection control. When not working he can be found sailing, fishing or kayaking. Learn more about Barry and connect via Email or on Linkedin.

 

Comments

This is a great primer on how and why we (should) do what we do. Unfortunately, many healthcare providers conveniently ignore the science and contribute to the spread despite the warnings. An additional approach we are seeing as a result of the 2003 SARS outbreak is the use of oxygen therapy masks that contain an integral filter to decrease the spread of those droplets. Many healthcare protocols are written without consideration to those caring for patients with undiagnosed respiratory conditions who require oxygen therapy (and there are millions every day). If the patient requires an oxygen mask due to their illness, they cannot be effectively masked. An additional layer of containment adds to the existing multilayered strategy of decreasing the spread at the source.
Posted @ Wednesday, February 20, 2013 9:18 AM by Edward Reesor
Thanks for your comment Edward, I am sure everyone involved in hospital infection control is reviewing their airborne precautions. Masks and hand hygiene were an important ingredient in beating SARS the last time around. We are a bit ahead of the curve this time and have more tools to fight it, but with your comment I pulled out my old issue of Emerging Infectious Diseases Vol. 12, No. 6, June 2006: 1003-04, on how to make an N95 filtration mask out of a heavy T-shirt.
Posted @ Wednesday, February 20, 2013 11:01 AM by Barry Michaels
You mean our cucumber based, green cleaning chemicals aren't cleaning well enough to impede the transmission of disease???? NO KIDDING!  
 
It's not enough that every day schools all over the US are closing because too many kids are sick? What's a few dead kids anyway, as long as we can say we are "Green" the body count is strictly secondary to the elevation of the Green movement.
Posted @ Wednesday, February 20, 2013 11:09 AM by Ed Selkow
Another excellent and very informative article from Barry, thank you for that. 
This article highlights very well the fact that we cannot afford counting only on our first lines of defense (i.e. antibodies such as Immunoglobulin A contained in the nasal mucus), as well as the second ones (immune and non-immune systems) to fight infections. 
Without being absolutely obsessed by hygiene, there are elementary rules to respect to reduce the risk of getting infected. Direct contamination is sometimes difficult to avoid, especially in the kind of stuffy atmosphere you may have to deal with in buses in rush hours. 
Indirect contamination (from surfaces) is definitely easier to manage. Just think about the number of people who cough and sneeze in their hands and then touch surfaces like bus handles or trolley handles. Everyone should be scared of that. Anyway, I guess that, slowly but surely, more and more people will soon understand that, using prophylactic methods such as wearing protective masks (not yet in our occidental culture), as well as washing and sanitizing hands, not only means “self-protection” but also means “behaving in a socially conscious fashion”.
Posted @ Wednesday, February 20, 2013 11:38 AM by Dr Grascha Pierre
Excellent and informative article! I would not wish to draw any negative conclusions about the effectiveness or otherwise of so-called "green chemistry" in regard to antimicrobial effectiveness. These are two essentially unrelated aspects and it is perfectly possible for a formulation to be both effective and environmentally responsible. Firstly as the article points out, simple, frequent washing with soap and water is highly effective in many instances. Modern foaming soap formulations are especially low in environmental impact due to reduced requirement for chamical thickeners and much improved spreadability and rinsability.  
 
Alcohol sanitizers are also very useful and environmentally reasonable. While many historical antimicrobial actives do have environmental question marks as we learn more about their long term impacts, alternatives are available (e.g. Accelerated Hydrogen Peroxide) that are very safe, very effective and very green. 
 
Certainly one should avoid poor quality cleansing products where green claims stand in place of proper formulation, but one should not assume that genuine efforts on the part of industry to reduce environmental impact is necessarily at the expense of efficacy.
Posted @ Friday, February 22, 2013 4:05 PM by Dr John Hines
Nice article, thanks! Is viral meningitis spread in the same way as influenza, and is it something to worry about? I know bacterial meningitis can be dangerous, but not as sure about viral?
Posted @ Tuesday, March 12, 2013 12:24 PM by Chris Warford
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