TABLE 2. Rank order (most common to least common) of etiology, water system, water source, predominant illness, and deficiencies associated with 42 drinking water outbreaks and 1,006 outbreak-related cases of illness — United States, 2013–2014.
| Characteristic/Rank | Outbreaks (N = 42) |
Cases (N = 1,006) |
||
|---|---|---|---|---|
| Category | No. (%) | Category | No. (%) | |
|
Etiology
| ||||
| 1 |
Bacteria, Legionella |
24 (57.1) |
Chemical/Toxin |
499 (49.6) |
| 2 |
Parasites |
8 (19.1) |
Parasites |
289 (28.7) |
| 3 |
Chemical/Toxin |
4 (9.5) |
Bacteria, Legionella |
130 (12.9) |
| 4 |
Viruses |
3 (7.1) |
Viruses |
68 (6.8) |
| 5 |
Bacteria, non-Legionella |
1 (2.4) |
Multiple bacteria |
12 (1.2) |
| 6 |
Multiple bacteria |
1 (2.4) |
Bacteria, non-Legionella |
5 (0.5) |
| 7 |
Unknown |
1 (2.4) |
Unknown |
3 (0.3) |
|
Water system*
| ||||
| 1 |
Community |
30 (71.4) |
Community |
759 (75.4) |
| 2 |
Noncommunity |
5 (11.9) |
Individual |
124 (12.3) |
| 3 |
Individual |
3 (7.1) |
Noncommunity |
115 (11.4) |
| 4 |
Unknown |
3 (7.1) |
Unknown |
6 (0.6) |
| 5 |
Bottled |
1 (2.4) |
Bottled |
2 (0.2) |
|
Water source
| ||||
| 1 |
Ground water |
14 (33.3) |
Surface water |
795 (79.0) |
| 2 |
Surface water |
14 (33.3) |
Ground water |
157 (15.6) |
| 3 |
Unknown |
12 (28.6) |
Unknown |
39 (3.9) |
| 4 |
Mixed† |
1 (2.4) |
Mixed |
12 (1.2) |
| 5 |
Unreported |
1 (2.4) |
Unreported |
3 (0.3) |
|
Predominant illness
§
| ||||
| 1 |
ARI |
24 (57.1) |
AGI |
862 (85.7) |
| 2 |
AGI |
17 (40.5) |
ARI |
130 (12.9) |
| 3 |
AGI; Neuro |
1 (2.4) |
AGI; Neuro |
14 (1.4) |
|
Deficiency
¶
| ||||
| 1 |
Legionella spp. in drinking water system** |
23 (54.8) |
Treatment not expected to remove contaminant |
485 (48.2) |
| 2 |
Unknown/Insufficient information†† |
7 (16.7) |
Unknown/Insufficient information |
143 (14.2) |
| 3 |
Multiple§§ |
3 (7.1) |
Legionella spp. in drinking water system |
126 (12.5) |
| 4 |
Treatment not expected to remove contaminant¶¶ |
3 (7.1) |
Treatment deficiency |
119 (11.8) |
| 5 |
Untreated ground water*** |
3 (7.1) |
Untreated ground water |
70 (7.0) |
| 6 |
Distribution system††† |
1 (2.4) |
Multiple |
42 (4.2) |
| 7 |
Premises plumbing system§§§ |
1 (2.4) |
Premise plumbing system |
14 (1.4) |
| 8 | Treatment deficiency¶¶¶ | 1 (2.4) | Distribution system | 7 (0.7) |
Abbreviations: AGI = acute gastrointestinal illness; ARI = acute respiratory illness; Neuro = neurologic illnesses, conditions, or symptoms (e.g., meningitis).
* Community and noncommunity water systems are public water systems that have ≥15 service connections or serve an average of ≥25 residents for ≥60 days per year. A community water system serves year-round residents of a community, subdivision, or mobile home park. A noncommunity water system serves an institution, industry, camp, park, hotel, or business and can be nontransient or transient. Nontransient systems serve ≥25 of the same persons for ≥6 months of the year but not year-round (e.g., factories and schools) whereas transient systems provide water to places in which persons do not remain for long periods of time (e.g., restaurants, highway rest stations, and parks). Individual water systems are small systems not owned or operated by a water utility that have <15 connections or serve <25 persons.
† Includes outbreaks with mixed water sources (i.e., ground water and surface water).
§ The category of illness reported by ≥50% of ill respondents; all legionellosis outbreaks were categorized as ARI.
¶ Outbreaks are assigned one or more deficiency classifications. https://www.cdc.gov/healthywater/surveillance/deficiency-classification.html.
** Deficiency 5A. Drinking water, contamination of water at points not under the jurisdiction of a water utility or at the point of use: Legionella spp. in water system, drinking water.
†† Deficiency 99. Unknown/Insufficient information.
§§ Multiple deficiency classifications were assigned to three outbreaks. One outbreak had deficiency 2, 3 one had 3, 4, and one had 5a, 7 (deficiency in building/home-specific water treatment after the water meter or property line).
¶¶ Deficiency 13a. Current treatment processes not expected to remove a chemical contaminant: ground water.
*** Deficiency 2. Drinking water, contamination of water at/in the water source, treatment facility, or distribution system: untreated ground water.
††† Deficiency 4. Drinking water, contamination of water at/in the water source, treatment facility, or distribution system: Distribution system deficiency, including storage (e.g., cross-connection, backflow, and contamination of water mains during construction or repair).
§§§ Deficiency 6. Drinking water, contamination of water at points not under the jurisdiction of a water utility or at the point of use; plumbing system deficiency after the water meter or property line (e.g., cross-connection, backflow, or corrosion products).
¶¶¶ Deficiency 3. Treatment deficiency (e.g., temporary interruption of disinfection, chronically inadequate disinfection, or inadequate or no filtration).