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General Biosafety Training (EHS 0739)
EHS 0739 SITE MAP
BIOSAFETY TRAINING INTRODUCTION
PERSONAL PROTECTIVE EQUIPMENT & EXPOSURE CONTROL
BIOSAFETY INCIDENT AND ACCIDENT RESPONSE
QUESTIONS
BIOSAFETY MANUAL
 
 

Infectious Dose

The infectious dose for man varies and is dependent on the type of agent, the route of exposure, and the health status of the host in addition to dose.  This interrelationship is important because it helps to explain why not all laboratory workers who handle infectious agents become ill.  Viruses pose a greater hazard than the other agents because the infectious dose for man is lower than that for other agents.  Data to illustrate this are presented in the following Table.

Infectious Dose for Man

Disease or Agent

Dosea

Route of inoculation

Scrub typhus

3

Intradermal

Q fever

10

Inhalation

Tularemia

10

Inhalation

Malaria

10

Intravenous

Syphilis

57

Intradermal

Typhoid fever

105

Ingestion

Cholera

108

Ingestion

Escherichia coli

108

Ingestion

Shigellosis

109

Ingestion

Measles

0.2b

Inhalation

Venezuelan encephalitis

1c

Subcutaneous

Polio virus 1

2d

Ingestion

Coxsackie A21

18

Inhalation

Influenza A2

790

Inhalation

 

  1. Dose in number of organisms.
  2. Median infectious dose in children.
  3. Guinea pig infective dose.
  4. Median infectious dose.

With the current expansion of interest in diagnostic and research virology, and in view of the aerosol production capability of standard laboratory techniques as mentioned previously, a corresponding increase in laboratory-acquired viral illnesses would be expected among personnel who handle these agents. 

The large doses of bacterial agents required to produce disease via ingestion help to explain why all microbiologists do not become clinically ill from their cultures.  In addition, the very low inhalation dose for certain agents (e.g., F. tularensis, C. burnetti, measles virus, and coxsackie A21 virus) points out the importance of preventing aerosol formation in the laboratory environment and illustrates why the direct cause of the majority of laboratory associated infections may go undetected.

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