2. Accidents as a cause of laboratory infections

A review of the available literature indicates that 80% of laboratory acquired infections are due to unknown or unrecognized causes. This means that only about 20% of laboratory- acquired infections can be related to some causative or defined event (or accident).

The majority of these accidents were caused by human error (about 80%), while about 20% were caused by equipment failure. Accidents may occur when the sequence of actions in the processes or the timing is wrong, when activities are executed at an abnormal speed, when there is a mistake in the quantities used, or when a combination of the above, in addition to other factors, occurs.

The common types of accidents that cause infections were reviewed by Collins and are shown in Table A. In an earlier survey of 3700 infections, oral aspiration through pipettes was one of the prime causes of laboratory-acquired infections.

Table A: Accidents that cause infection

Cause No.	Type of accident	No. of infected persons	%
1	Spillage and splashes	188	26.7
2	Needle and syringe	177	25.2
3	Sharp object, broken glass	112	15.9
4	Bite or scratch from animals or ectoparasites	95	13.5
5	Aspiration through pipette	92	13.1
6	Others	39	5.5
	T O T A L	703	100

The decrease in the percentage of accidents involving mouth pipetting can be attributed to the variety of pipetting aids developed and now commonly used by laboratory workers.