WHAT’S IN AMERICA’S WATER


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Annual Water Quality Report for the City of:

San Diego

Los Angeles

San Francisco

Waterborne Disease Outbreaks Waterborne Disease Outbreaks in the U.S., 1971 through 1994

Etiology of Waterborne Outbreaks 
In the United States, 1971-1994 
Etiology 
Outbreaks 
Cases of Illness 
Gastroenteritis, undefined 
347 
83,107 
Giardia 
127 
27,259 
Chemical 
71 
4,333 
Shigella 
66 
10,731 
Hepatitis A 
30 
853 
Norwalk Agent 
24 
10,908 
Cryptosporidium 
19 
421,202 
Campylobacter 
16 
5,480 
Salmonella, non-typhoid 
13 
2,995 
Salmonella, typhi  
7 
293 
E. coli 0157:H7 
3 
489 
Other Etiologies 
17 
3,128 
Totals 
7140 
571,373 

An increasing number of outbreaks during recent years have been caused by Giardia lamblia and Cryptosporidum parvum. In 1991 and 1992 for the thirteenth and fourteenth consecutive years, Giardia lamblia was the most frequently identified etiology of waterborne outbreaks in the U.S. Cryptosporidum parvum was the second most commonly identified etiologic agent in 1991, 1992, and 1994. In 1993 it was the most frequently identified etiology due to the massive Cryptosporidiosis outbreak in Milwaukee (400,000 illnesses).