Wednesday, June 1, 2011


  Viruses, especially the enveloped viruses, are generally fairly labile and do not survive too well outside their host cells. However, some (eg. hepatitis B virus) are very resistant to inactivation, and health care workers need to take special precautions to avoid transmitting such infections.
  Means of prevention of the spread of infection, and sterilisation and disinfection of viruses, are very similar to those principles that are applied in bacteriology.

Spread may be by

1) inhalation of aerosolised "droplets";

2) ingestion;

3) direct contact (skin/mucous membrane to skin/mucous membrane), or

4) indirect contact via intermediate "fomites".

Moist heat (autoclaving 120*C x 20 minutes) or dry heat (oven, 180*C for 60 minutes) are effective against all viruses - lesser degrees of heat may inactivate many viruses (eg. simple boiling) but may not reliably inactivate resistant viruses especially if times of exposure are short.

Chemicals: halogens, especially chlorine as hypochlorite are effective against viruses but corrosive on instruments where activated gluteraldehyde ("Cidex") is preferred.

Detergents and lipid solvents inactivate readily the enveloped viruses which need an intact envelope for effective cell adsorption.

Phenolic disinfectants damage proteins and thus inactivate bacteria but do not affect nucleic acids. Phenolics are not recommended for viral disinfection.


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