91 
The frequency of laboratory-acquired infections for four periods of 
operation at Ft. Detrick are summarized in the table below. These 
periods were selected because the safe laboratory practices and contain- 
ment equipment used during these periods approximate those required 
by the NIH Guidelines for Pi, P2, P3, and P4 physical containment 
levels. In considering this experience, it must be emphasized that the 
majority of agents handled at Ft. Detrick are now classified by the CDC 
as class 3 and class 4 human pathogens, the use of which is prohibited 
by the Guidelines in recombinant DNA research. 
ESTIMATED LABORATORY -ACQUIRED INFECTION RATES 
AMONG FORT DETRICK LABORATORY PERSONNEL 
Laboratory -acquired 
Approximate physical infections per million 
Period 
Group at risk 
containment level 
man-hours worked* 
1943- 
45 
All laboratory -admitted 
personnel** 
PI 
35^ 
1954- 
58 
All laboratory -admitted 
civilians 
P2 
1960- 
62 
All laboratory-admitted 
civilians 
P3 
2< 1 > 
1960- 
69 
All laboratory -admitted 
personnel in Building 
1412B 
P4 
i< 2 > 
* Includes subclinical infections and mild illnesses where hospitalization 
was not required. **During this time, personnel were predominantly 
military rather than civilian; after 1946 the reverse was true. 
This experience demonstrates a reduction in laboratory-acquired 
infections with increasing levels of physical containment. It also 
demonstrates that when known hazardous agents are handled, the risk 
of a laboratory-acquired infection cannot be totally eliminated. 
