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Viruses - What is a virus and can any
air purifier actually offer protection?
Viruses are not considered living organisms, however
they are dependent upon living cells for replication.
The structure of a virus includes the envelope
which constitutes proteins and genetic material, which can be DNA
or RNA. All these components are Thermo sensitive.
The genetic material and the proteins have complex
structures and a change in this structure may result in loss of
their ability to function. This process is called denaturizing.
There are two basic ways to to achieve this, either by changing
PH or temperature.
There are a great deal of studies focusing on
virus deactivation through heat. For example, the HIV virus can
be killed in blood when exposed for as little as 0.0006 seconds
at 77degrees C.(1)
In another study, it was discovered that exposure
of parvovirus and phage phiX174 for 90 seconds at 103 degrees C
completely deactivated those viruses (2).
SARS Virus
The SARS virus ( the agent of severe acute respiratory
syndrome) has thermo sensitive proteins in its envelope which can
be totally denaturized at 55 degrees C. The same temperature at
which the SARS virus was reported to be de-activated (5).
The Flu Virus
The Influenza virus, ( the main flu agent ) has proteins,
necessary for the infection that are sensitive to variations of
pH and temperature variable between 55-70 degrees C (6).
Herpes Virus
In the case of the herpes virus, high temperatures inhibit the release
of proteins neccessary for the success of the infection.
Sincytyal Virus
Airborne viruses are no different, One study of the respiratory
virus sincytyal ( the major cause of wheezing in children less than
2 years old ) showed that when the virus is exposed to 65 degrees
C for 45 minutes, the infection is affected and conformational proteins
are changed, resulting in less release by the host, of substances
responsible for the inflamation, hyper responsivness and damage
of the airways.
Avian Flu
The virus responsible for bird flu can be spread from poultry
to humans and up until now around 20 million chickens have been
killed in an attempt to control the virus (10).
Since 1997 , more than 100 cases of the disease
in humans have been reported, resulting in more than 50 deaths (8).
Experts are concerned about the production of a pandemic new strain
of the virus which could result from mixing avian and human strains
of the virus.
It is suspected that the virus could infect someone
who is already infected with a human influenza type A virus resulting
in genetic rearrangement and a highly virulent novel pathogen which
could be easily transmitted from human to human.
Transmission and Symptoms.
All birds are succeptible to the avian virus and some types
of wild bird are a natural carrier of the Infuenza type A virus.They
have a large amount of avian virus in their secretion, saliva and
feces that can contaminate domestic poultry upon contact.
In addition to this their droppings or saliva
may contaminate water, rivers, food and even humans. Infected droplets
may settle on conjunctival, nasopharyngeal or other respiratory
mucosal epithelium in humans leading to symptons ranging from typical
flu like symptons ( e.g ., fever, cough, sore throat and muscle
aches ) to eye infections ( conjunctivitis ), pneumonia, acute respiratory
distress, viral pneumonia and other severe and life threatening
complications. (13).
Avian Flu characteristics and heat sensitivity.
The avian virus, H5N1, is a negative sense single-stran
RNA virus (12), which has two types of proteins: hemagglutinin (HA)
and neuraminidase (NA)(13). It is known that the virus can be de-activated
by 56 degrees C in 3 hours and 60 degreesC in 30 minutes (8). Thus
an increase of only 4 degrees speeds the time of de-activation by
about 85%.
What type of Air Purifier will offer me
the best protection from the above viruses?
Above we have listed a only a few examples of virus de-activation
using heat.
Since 1977 studies have shown that the higher
the temperature the faster the proteins get denaturized(7).In all
of these cases the temperatures used were well below the 200 degrees
C which is generated by the HETD ceramic core which can only be
found inside Airfree air purifers.
Therefore we would infer that either the
Airfree
P80, P125
or WM60
air purifers which utilise heat up to 200 degrees C to destroy airborne
contamination may well be succesful in the de-activation of the
virus proteins in most cases resulting in the loss of their ability
to function.
Bibliographical references.
1- Charm SE, Landau S, Williams B, Horowitz B, Prince AM, Pascual
D. High-temperature short-time heat inactivation of HIV
and other viruses in human blood plasma. Vox Sang. 1992;62(1):12-20.
2- Lelie PN, Reesink HW, Lucas CJ. Inactivation of 12 viruses by
heating steps applied during manufacture of a hepatitis B
vaccine.
J Med Virol. 1987 Nov;23(3):297-301.
3- Morrison EE, Wang YF, Meredith DM. Phosphorylation of structural
components promotes dissociation of the herpes simplex
virus type 1 tegument. J Virol. 1998 Sep;72(9):7108-14.
4- Jaovisidha P, Peeples ME, Brees AA, Carpenter LR, Moy JN. Respiratory
syncytial virus stimulates neutrophil degranulation
and chemokine release. J Immunol. 1999 Sep 1;163(5):2816-20.
5 -Wang Y, Wu X, Wang Y, Li B, Zhou H, Yuan G, Fu Y, Luo Y. Low
stability of nucleocapsid protein in SARS virus. Biochemistry.
2004 Aug 31;43(34):11103-8.
6- Epand RM, Epand RF. The Thermal Denaturation of Influenza Virus
and its
Relationship to Membrane Fusion. Biochemical Journal Immediate Publication.
Published on 7 May 2002 as manuscript
BJ20020290.
7- Palumbo SA, Smith JL, Kissinger JC. Destruction of Staphylococcus
aureus During Frankfurter Processing. Applied and
environmental micorbiology, 1977:740-744.
8- Shih-Wen Hung, I-Yin Lin, Tzong-Luen Wang. Emerging Infectious
Disease (1): Avian Influenza. Med. 2005;3 Suppl 2:S40-
S46
9- Fleck, F. Avian flu virus could evolve into dangerous human pathogen,
experts fear. Bull World Health Organ, mar. 2004; 82
(3):236-237. ISSN 0042-9686.
10- Abott A., Pearson H. Fear of human pandemic grows as bird flu
sweeps through Asia. Nature, febr 2004; (427): 472-73.
11- Andresen M. Avian flu: WHO prepares for the worst. CMAJ. 2004
Mar 2;170(5):777.
12- KY Yuen, SSY Wong. Human infection by avian influenza A H5N1.
Hong Kong Med J 2005;11:189-99
13-Center for Disease Control and Prevention. Avian Influenza Infection
in Humans. October 17, 2005.
http://www.cdc.gov/flu/avian/gen-info/avian-flu-humans.htm
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