CHEMICAL AND PHYSICAL PROPERTIES OF VIRUSES

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Table 1 outlines some of the basic chemical and physical properties of viruses. These chemical and physical properties of viruses are critical to their survival, replication and control in the environment. They also shed some light on how best viruses, especially pathogenic viruses can be adequately controlled and possibly eradicated or eliminated from inanimate objects, materials or surfaces. Viruses have several physicochemical properties including pH, molecular size or mass, stability to heat and susceptibility to organic solvents such as ether and other physical or chemical agents that may affect their proper development and replication. They react to various chemical and physical factors in their environment.

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 Table 1. Overview of the physical and chemical properties of viruses

PHYSICAL PROPERTIESCHEMICAL PROPERTIES
  
Temperature: Viruses can be inactivated at high temperatures. Several viruses are susceptible to varying degrees of temperature; and this has been successfully used to inactivate viruses for several virological manipulation and even to achieve sterility at a particular time or place. While some viruses can be inactivated at a shorter time (e.g., 30 min) at a temperature range of 50-60oC, others can be inactivated at the same temperature for a longer time. However, most viruses are inactivated at 100oC at a lesser time interval (e.g., 5-10 min).  Formaldehyde: Formaldehyde is a chemical that has strong inactivation property on virtually all viruses. Virtually all viruses are susceptible to formaldehyde; and this chemical is usually used as formalin in most disinfectants. Alcohol or ethanol, ethylene diamine and isopropanol are examples of other inactivating agents used to deactivate viruses but with low efficacy. Formaldehyde destroys viruses by reacting with viral genomes.   
Freezing and thawing: The infectivity or degree of virulence of pathogenic viruses can be inactivated when such viruses undergo freezing and thawing. Freezing and thawing are typical physical parameters that generally affect the infectivity and/or antigenic features of viruses. Therefore, frozen samples containing viruses are usually allowed to thaw on ice during experiments in order to avoid losing their physical and/or chemical properties.  Ether: Ether is another category of chemical agents that can inactivate viruses. Ether inactivate some classes of viruses especially those with envelopes. Some non-enveloped viruses (i.e., naked viruses) are ether-resistant. The susceptibility of viruses to ether is used to distinguish viruses since naked viruses are mostly ether-resistant while enveloped viruses are ether-sensitive.
Radiation: Radiation is generally used to inactivate various viruses. Ultraviolet (UV) light,x-rays, ultrasonicvibrations and sunlight are typical examples of different forms of radiation that can be used to inactivate a virus. However, the inactivation of the virus is largely dependent on the intensity of the radiation used. The higher the intensity of the radiation, the more effective the efficacy of the radiation on the virus. Radiation affects the replication processes of viruses.Chlorine compounds: Chlorine compounds including sodium hypochlorite or bleach are used to inactivate viruses. Bleach is a common household disinfectant that is also used in hospitals and industries to disinfect inanimate surfaces. They have the potential to inactivate viruses by interfering with the replication process of a virus.      

These chemical and physical factors of viruses as outline in Table 2.2 are used to determine the physical and chemical properties of viruses as well as to inactivate them in the hospital environment and elsewhere (Table 1).

METHODS USED FOR THE INACTIVATION OF VIRUSES

Several reasons exist for the inactivation of viruses, either to use them for a useful purpose such as in studying varying properties of viruses or to inactivate and attenuate their pathogenicity or virulence so that they do not cause harm to a living host including humans, animals and plants. Some of the major reasons for inactivating viruses so that they do not become pathogenic upon their usage for research or other activities are highlighted in this section.

  • Viruses are inactivated during vaccine production so that inactivated vaccines containing killed viruses can be produced.
  • Viruses are inactivated in order to make some human consumables such as water to be safe for consumption. This is usually applied in water producing industries and water distribution companies to inactivate pathogenic viruses that may be present in the water supply chain.
  • Viruses are inactivated during the disinfection of work benches or surfaces in the laboratory, hospitals and in our homes especially when disinfectants (with putative antiviral and/or antimicrobial action) are used for cleaning dirty surfaces.
  • They are also inactivated during the sterilization of hospital equipment, laboratory equipment and other health supplies. Some viruses lose their virulence when they are subjected to high temperature and pressure as that obtainable during the sterilization of heat-stable materials or equipment in the hospital or laboratory.      

Further reading

Acheson N.H (2011). Fundamentals of Molecular Virology. Second edition. John Wiley and Sons Limited, West Sussex, United Kingdom.

Brian W.J Mahy (2001). A Dictionary of Virology. Third edition. Academic Press, California, USA.

Cann A.J (2011). Principles of Molecular Virology. Fifth edition. Academic Press, San Diego, United States.

Carter J and Saunders V (2013). Virology: Principles and Applications. Second edition. Wiley-Blackwell, New Jersey, United States.

Dimmock N (2015). Introduction to Modern Virology. Seventh edition. Wiley-Blackwell, New Jersey, United States.

Kudesia G and Wreghitt T (2009). Clinical and Diagnostic Virology. Cambridge University Press, New York, USA. 

Marty A.M, Jahrling P.B and Geisbert T.W (2006). Viral hemorrhagic fevers. Clin Lab Med, 26(2):345–386.

Strauss J.H and Straus E.G (2008). Viruses and Human Diseases. 2nd edition. Elsevier Academic Press Publications, Oxford, UK.

Zuckerman A.J, Banatvala J.E, Schoub B.D, Grifiths P.D and Mortimer P (2009). Principles and Practice of Clinical Virology. Sixth edition. John Wiley and Sons Ltd Publication, UK.

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