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No statistically significant duration ratios and SDs ratios were observed among NEEAR water recreators swallowing water and swimming compared to waders for all semi-continuous severity outcomes using the ZINB model (Table 4). However, enterococci by qPCR appeared to be an important predictor of duration of GI symptoms (duration ratio = 1.54 (95% CI: 1.04, 2.28)) and GI SDs (SDs ratio = 1.42 (95% CI: 1.10, 1.84)) in the ZINB models (Table 4). Results of logistic regression showed that major responses to symptoms (hospitalization, ED visit, HCP visit or phone call, prescription medication use, or missing work or missing daily activities, vs. only taking OTC medications or having no response to symptoms) were more likely among those with greater water exposure. Greater water exposure among NEEAR participants (swimming with swallowing water vs. wading) was associated with increased odds of reporting major responses to symptoms (OR = 1.57 (95% CI: 1.27, 1.95)). However, microbial measures of water quality concentrations were not associated with a major response to symptoms among NEEAR participants. No differences were observed for any outcome when assessing water quality in quartiles, rather than a dichotomous outcome among NEEAR participants (Supplementary Table S2, available with the online version of this paper).

Table 4

Relationship between symptom severity and water exposure or water quality among NEEAR water recreators

Severity outcomeExposureZINBLogistic regression
Ratioa (95% CI)Odds ratiob (95% CI)
Duration of GI symptoms 
n = 16,386 Water ingested vs. wading 0.89 (0.59, 1.33) – 
Swimming vs. wading 0.97 (0.71, 1.34) – 
n = 16,378 Enterococci qPCR, 75th percentile 1.54 (1.04, 2.28) – 
n = 16,378 Enterococci culture, 75th percentile 1.31 (0.96, 1.78) – 
GI SDs 
n = 16,386 Water ingested vs. wading 0.99 (0.74, 1.32) – 
Swimming vs. wading 1.05 (0.83, 1.31) – 
n = 16,378 Enterococci qPCR, 75th percentile 1.42 (1.10, 1.84) – 
n = 16,378 Enterococci culture, 75th percentile 1.18 (0.96, 1.45) – 
Total SDsc 
n = 17,061 Water ingested vs. wading 1.02 (0.85, 1.25) – 
Swimming vs. wading 0.93 (0.81, 1.08) – 
n = 16,868 Enterococci qPCR, 75th percentile 1.16 (0.98, 1.38) – 
n = 16,898 Enterococci culture, 75th percentile 0.98 (0.85, 1.12) – 
Major vs. minor responses to symptomsd 
n = 17,037 Water ingested vs. wading – 1.57 (1.27, 1.95) 
Swimming vs. wading – 1.12 (0.95, 1.32) 
n = 16,842 Enterococci qPCR, 75th percentile – 1.12 (0.93,1.35) 
n = 16,842 Enterococci culture, 75th percentile – 1.00 (0.84, 1.17) 
Severity outcomeExposureZINBLogistic regression
Ratioa (95% CI)Odds ratiob (95% CI)
Duration of GI symptoms 
n = 16,386 Water ingested vs. wading 0.89 (0.59, 1.33) – 
Swimming vs. wading 0.97 (0.71, 1.34) – 
n = 16,378 Enterococci qPCR, 75th percentile 1.54 (1.04, 2.28) – 
n = 16,378 Enterococci culture, 75th percentile 1.31 (0.96, 1.78) – 
GI SDs 
n = 16,386 Water ingested vs. wading 0.99 (0.74, 1.32) – 
Swimming vs. wading 1.05 (0.83, 1.31) – 
n = 16,378 Enterococci qPCR, 75th percentile 1.42 (1.10, 1.84) – 
n = 16,378 Enterococci culture, 75th percentile 1.18 (0.96, 1.45) – 
Total SDsc 
n = 17,061 Water ingested vs. wading 1.02 (0.85, 1.25) – 
Swimming vs. wading 0.93 (0.81, 1.08) – 
n = 16,868 Enterococci qPCR, 75th percentile 1.16 (0.98, 1.38) – 
n = 16,898 Enterococci culture, 75th percentile 0.98 (0.85, 1.12) – 
Major vs. minor responses to symptomsd 
n = 17,037 Water ingested vs. wading – 1.57 (1.27, 1.95) 
Swimming vs. wading – 1.12 (0.95, 1.32) 
n = 16,842 Enterococci qPCR, 75th percentile – 1.12 (0.93,1.35) 
n = 16,842 Enterococci culture, 75th percentile – 1.00 (0.84, 1.17) 

aRatio refers to duration ratio or SDs ratio, control for beach as a fixed effect.

bOdds ratio evaluating odds of severe illness in exposed versus unexposed (reference group), control for beach as a fixed effect and household clustering.

cIncludes GI and non-GI symptoms.

dED or hospitalization, contact with HCP, take prescription, lost work or daily activities vs. OTC use only or no response.

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