Sources of Waterborne Disease Outbreaks,GWS, 1971-1994

Table 1.

Type of Contamination	Total Number of Outbreaks	Percentage of Total
Source Contamination	287	81%
Untreated Ground Water	158	45%
Disinfected Ground Water	126	35%
Filtered Ground Water	3	1%
Distribution System Contamination	50	14%
Inadequate Control of Chemical Feed	8	2%
Miscellaneous, Unknown Cause	11	3%
Total	356	100%

Table 2. Sources of Waterborne Disease Outbreaks in Community, GWS, 1971-1994

 

Type of Contamination	Outbreaks in Community Systems	Percentage of Total
Source Contamination	70	62%
Untreated Ground Water	31	27%
Disinfected Ground Water	36	32%
Filtered Ground Water	3	3%
Distribution System Contamination	35	31%
Inadequate Control of Chemical Feed	5	4%
Miscellaneous, Unknown Cause	3	3%
Total	113	100%

Table 3. Sources of Waterborne Disease Outbreaks in Non-Community, GWS, 1971-1994

 

Type of Contamination	Outbreaks in Non-Community Systems	Percentage of Total
Source Contamination	217	89%
Untreated Ground Water	127	52%
Disinfected Ground Water	90	37%
Filtered Ground Water	0	0%
Distribution System Contamination	15	7%
Inadequate Control of Chemical Feed	3	1%
Miscellaneous, Unknown Cause	8	3%
Total	243	100%

Note: The source water could not be identified for 21 community and 6 non-community systems experiencing outbreaks; therefore, these systems are not included in Tables 1-3.

Table 4. Etiology of Waterborne Disease Outbreaks in Community and Non-Community Systems 1971-1994

 

Etiologic Agent	Outbreaks in Community Systems	Outbreaks in Non-Community Systems
Campylobacteria	5	5
Chemical	17	5
Cryptosporidium	3	1
E. coli	1	1
E. histolytica	1
Gastroenteritis, Undefined	40	183
Giardia	15	7
Hepatitis A	8	9
Norwalk virus	4	12
Salmonella	5	1
Salmonella, non-typhoid	4
Shigella	10	17
S. typhi		1
Yersinia		1
TOTAL	113	243

Note: The source water could not be identified for 6 non-community and 21 community systems experiencing outbreaks; therefore, these systems are not included in the table.