Many of us are naturally concerned by the alarming spread of viruses in recent years, particularly the bird flu virus that is threatening to spread throughout Europe. The very young, the elderly and those with weakened immune systems are particularly at risk from these viruses.

Avian Flu

For more than a century, bird flu has circulated among birds, particularly domesticated fowl, but the new subtype A (H5N1) first appeared in 1997, the strain which can infect humans. The virus has strengthened and mutated, resulting in a contagion that can move from bird to human- but not yet from human to human. There is concern that if the virus infects someone who is already infected with a human flu virus, then a new highly virulent strain could result, that can be transmitted human to human.

Human cases of bird flu have caused infections and death across the globe as scientists struggle to identify the dangerous strains and prevent a fatal pandemic. About 20 million birds have been slaughtered in an attempt to stop the spread of the virus, which spreads by air, water, and soil. So far the virus can be caught only by people who are working with infected fowl, or in contact with infected rivers, poultry processing plants, etc. About 100 cases of the disease have been reported, resulting in about 50 deaths.

The symptoms range from fever, cough, sore throat, and muscle aches to eye infections (conjunctivitis), pneumonia, acute respiratory distress, viral pneumonia, and other severe and life-threatening complications.

Most health experts researching and fighting the incidence of human bird flu do not have an optimistic outlook. It is especially dangerous to humans as our immune system does not have the antibodies to handle something that used to be relegated to animals.

So far, doctors have been ineffective at treating the resultant respiratory infection, which can lead to fatalities as it takes hold with unprecedented force, settles in the lungs, and resists anti-viral and anti-bacterial medication.

Virus characteristics and heat instability.

Viruses aren’t considered living organisms, but they are very dependent on living cells to replicate. The structure of the virus includes the envelope which is constituted by proteins and the genetic material which can be DNA or RNA. All these components are thermosensible. The genetic material and the proteins have complex structures that are involved in their function and the change of their arrangements may result in lost of function. This process is called denaturation. There are two basic ways to do that: changing pH and temperature.

The avian virus, H5N1, is a negative-sense, single-stranded RNA virus 5, which has two types of proteins in its surface: hemagglutinin (HA) and neuraminidase (NA) 6. It is known from the literature that the virus can be inactivated by 56 oC in 3 hours and 60 oC in 30 minutes 1 . Thus, only four degrees of temperature elevation reduced the time of inactivation exposure about 85%.

About Viruses

What They Are
A virus is basically a tiny bundle of genetic material—either DNA or RNA—carried in a shell called the viral coat, or capsid, which is made up of bits of protein called capsomeres. Some viruses have an additional layer around this coat called an envelope. That's basically all there is to viruses. Viruses are strange things that straddle the fence between living and non-living. On the one hand, if they're floating around in the air or sitting on a doorknob, they're inert. They're about as alive as a rock. But if they come into contact with a suitable plant, animal or bacterial cell, they spring into action. They infect and take over the cell like pirates hijacking a ship.

What They Look Like
There are thousands of different viruses that come in a variety of shapes. Many are polyhedral, or multi-sided, a bit like a cut gem. Other viruses are shaped like spiky ovals or bricks with rounded corners. Some are like skinny sticks while others look like bits of looped string. Some are more complex and shaped like little lunar landing pods.

Where They're Found
Viruses are found on or in just about every material and environment on Earth from soil to water to air. They're basically found anywhere there are cells to infect. Viruses have evolved to infect every form of life, from animal to plant and from fungi to bacteria. However, viruses tend to be somewhat picky about what type of cells they infect. Plant viruses are not equipped to infect animal cells, for example, though a certain plant virus could infect a number of related plants. Sometimes, a virus may infect one creature and do no harm, but cause havoc when it gets into a different but closely enough related creature. For example, the Hantavirus is carried by deer mice without much noticeable effect on the rodents. But if Hantavirus gets into a person, it causes a dramatic and frequently deadly disease marked by excessive bleeding.

Single-Minded Mission
Viruses exist for one purpose only: to reproduce. To do that, they have to take over the reproductive machinery of suitable host cells.

Upon landing on an appropriate host cell, a virus gets its genetic material inside the cell either by tricking the host cell to pull it inside, like it would a nutrient molecule, or by fusing its viral coat with the host cell wall or membrane and releasing its genes inside. Some viruses inject their genes into the host cell, leaving their empty viral coats sitting outside.

If a virus is a DNA virus, its genetic material then inserts itself into the host cell's DNA. If the virus is an RNA virus, it must first turn its RNA into DNA using the host cell's machinery before inserting into the host DNA. The viral genes are then copied many, many times, using the machinery the host cell would normally use to reproduce its own DNA. The virus uses the host cell's enzymes to build new viral capsids and other viral proteins. The new viral genes and proteins then come together and assemble into whole new viruses. The new viruses are either released from the host cell without destroying the cell or eventually build up to a large enough number that they burst the host cell like an overfilled water balloon.

How to destroy Viruses

Viruses aren’t considered living organisms, but they are very dependent on living cells to replicate. The structure of the virus includes the envelope which is constituted by proteins and the genetic material which can be DNA or RNA. All these components are thermosensible. The genetic material and the proteins have complex structures that are involved in their function and the change of their arrangements may result in lost of function. This process is called denaturation. There are two basic ways to do that: changing pH and temperature.

The avian virus, H5N1, is a negative-sense, single-stranded RNA virus 5, which has two types of proteins in its surface: hemagglutinin (HA) and neuraminidase (NA) 6. It is known from the literature that the virus can be inactivated by 56 oC in 3 hours and 60 oC in 30 minutes 1 . Thus, only four degrees of temperature elevation reduced the time of inactivation exposure about 85%.

Viruses and heat inactivation

By Airfree Biological Division - Dr. Cristiane Minussi - October 4, 2005

-Overview

Viruses aren’t considered living organisms, but they are very dependent on living cells to replicate. The structure of the virus includes the envelope which is constituted by proteins and the genetic material which can be DNA or RNA. All these components are thermo sensible. The genetic material and the proteins have complex structures that are involved in their function and the change of their arrangements may result in lost of function. This process is called denaturizing. There are two basic ways to achieve it: change PH or temperature.

-Some examples: viruses and heat inactivation

There are many studies focusing in the viruses’ inactivation by applying heat. For example, the HIV virus can be killed in blood when exposed only for a 0.006 seconds at 77 degrees C1. In another study, the authors discovered that exposure of parvovirus and phage phiX174 for 90 seconds at 103 degrees C completely inactivated those viruses2. In the case of the Herpes virus, high temperatures inhibit the release of proteins necessary for the success of the infection3.

Airborne viruses aren’t different. One study with the respiratory sincytyal virus (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 ability is affected and conformational proteins are changed, resulting in less release, by the host, of substances responsible for the inflammation, hyper responsiveness and damage of the airways4. The SARS virus (causative agent of severe acute respiratory syndrome) has thermo sensible proteins in its envelope, which can be totally denaturized at 55 degrees C, the same temperature where SARS virus was also reported to be inactivated5. The influenza virus (the meaning flu agent), has proteins necessary for the infection, that are sensible to variations of pH and temperature (variation between 55-70 degrees C)6.

-Airfree and its HETD Ceramic Core internal temperature.

 Here, we have listed only few examples of viruses’ inactivation by heating and in all those cases, the temperatures were below the Airfree’s HETD ceramic core internal temperature of 200 degrees Celsius. Since 1977, studies have showed that the higher the temperature, the faster the proteins get denatured7. Therefore, we may infer that the Airfree purifier may be efficient in the inactivation of the virus proteins in most cases, resulting in the lost of the infection ability.

Bibliography

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.