Viruses are generally transmitted via surfaces and therefore the use of viricidal disinfectants on hard surfaces and viricidal antiseptics on skin is important. In addition, viruses are often associated with organic materials, such as secretions from the host, blood....
VIRICIDAL EFFECTS OF CHEMICAL AND PHYSICAL AGENTS ON VIRUSES
Viruses are generally
transmitted via surfaces and therefore the use of viricidal disinfectants on
hard surfaces and viricidal antiseptics on skin is important. In addition,
viruses are often associated with organic materials, such as secretions from the
host, blood, faeces etc., which enable them to persist on surfaces for longer
periods of time (weeks, months, and rarely years) and to survive better
viricidal challenges.
In general, viruses are
not particularly resistant to chemical or physical agents, although some
exceptions exist. In terms of susceptibility to viricidal agents, small non-enveloped
viruses (e.g. poliovirus) are more resistant than large enveloped viruses (e.g.
HIV, influenza), the lipid rich envelope being damaged easily by chemical and
physical agents. The susceptibility of large non-enveloped viruses varies, but
it is generally considered to be between that of the small naked and large
enveloped viruses, however some rotaviruses are proving particularly difficult
to destroy.
The viricidal activity
of biocides (antiseptics, disinfectants) varies and not all biocides show a
strong viricidal activity against non enveloped viruses (e.g. cationic biocides,
phenolics and alcohols). In addition, biocidal activity depends upon a number
of factors, such as concentration, contact time, presence of soiling, and formulation
(Chapters 18 and 19). Soiling is particularly an issue with water and foodborne
viruses. Indeed, even enveloped viruses can survive for many days on a soiled
surface even when exposed to biocides. The interactions between biocides and
viruses have been poorly studied. In general, viruses present only a few target
sites to biocides, mainly the envelope (when present), glycoproteins, the capsid
and viral nucleic acid . Some biocides (e.g. cationic) are likely to interact
with the envelope and glycoproteins, inhibiting viral infectivity, without
altering the viral capsid and genome. The main target site is most probably the
capsid which has been shown to be severely damaged in the presence of highly
reactive biocides such as aldehydes (e.g. glutaraldehyde) and oxidizing agents
(e.g. peracetic acid, hydrogen peroxide). Less reactive biocides, such as
quaternary ammonium compounds (QACs) and biguanides (e.g. chlorhexidine) have
been shown to damage viral capsid to a lesser extent, explaining the limited
activity of these agents against non-enveloped viruses. The viral genome is the
infectious part of the virus and is the ideal target for biocides. The destruction/alteration
of the viral nucleic acid would ensure complete viral inactivation. However,
only a limited number of reactive biocides, mainly oxidizing agents (e.g.
hydrogen peroxide, chlorine dioxide) have been shown to penetrate within the
capsid and damage viral nucleic acid, or to damage viral nucleic acid released
from a damaged capsid. The nature of the association of the viral nucleic acid
with the capsid also plays a role in the susceptibility of the virus to
chemical and physical agents. Viruses with a helical capsid structure might be
more susceptible since the destruction/alteration of capsid is more likely to
cause damage to the viral nucleic acid which is closely associated to this type
of structure.
Physical agents such as
heat and irradiation are viricidal and play an important role in the control of
viral contaminants in pharmaceutical products. Most viruses are susceptible to
exposure to temperatures above 60 °C for 30 minutes. Such susceptibility is
used for the inactivation of viral contaminants, such as HIV, in blood
products. However, other viruses such as the hepatitis B virus are less
susceptible and appropriate assurance of the absence of such a virus is needed.
Viruses survive well at low temperatures and they can be routinely stored at −40 °C to −70 °C. In addition to thermal processes, UV irradiation and
ionizing radiation (γray and accelerated
electrons) are viricidal mainly following the destruction of the viral nucleic acid.
Ionizing irradiation and thermal processes are used for terminal sterilization
processes applied to medical and pharmaceutical products .
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