Modelos por enfoque

Overview

We addressed the two aims using data from the National Epidemiological and

Environmental Assessment of Recreational (NEEAR) Water study, a prospective cohort study of 50,000+ visitors to four US freshwater and five marine beaches during 2003-2009. The aims estimated the association between exposure to human-associated Bacteroides (Aim 1) and chemical (Aim 2) fecal indicators in recreational waters and 10-12 day risk of self-reported illnesses. In our examination of these aims, we assessed type of water, level of swimming exposure, and additive interaction by the general fecal indicator, Enterococcus. Since the investigation of these aims involved secondary de-identified data analysis of NEEAR

participants, the UNC Public Health-Nursing institutional review board granted an exemption because it did not constitute human subjects research (13-2274).

Parent Study: National Epidemiological and Environmental Assessment of Recreational (NEEAR) Water Study

1. Study design and population

The NEEAR water study was a prospective cohort study that enrolled 54,250 men, women and children visiting four US freshwater and five marine beaches during 2003-2009 to

examine associations between swimming exposure, water quality and swimming-associated illnesses. The study also collected and analyzed numerous chemical and microbial fecal indicators of water quality. Study design, population, and data collection details have been previously published (56,57,96) but is summarized in detail below.

2. Beach descriptions

The NEEAR study focused on beaches impacted by nearby sewage effluents because such pollution is believed to contain potential human fecal contamination and cause the highest human illness risks (97). Although it was conducted at nine beaches, this secondary analysis focuses on the seven beaches studied between 2003 and 2007. In 2003 and 2004, NEEAR studies were conducted at four freshwater beaches: Huntington Beach on Lake Erie near Cleveland, Ohio; West Beach on Lake Michigan at Indiana Dunes National Seashore in Portage, Indiana; Silver Beach on Lake Michigan near St. Joseph, Michigan; and Washington Park Beach on Lake Michigan in Michigan City, Indiana. In 2005 and 2007, NEEAR studies were conducted at three temperate marine beaches: Edgewater Beach near Biloxi, Mississippi; Fairhope Municipal Beach in Fairhope, Alabama; and Goddard Beach near Warwick, Rhode Island.

Beaches that were impacted by sources of human fecal contamination were specifically selected. All of the beaches were located within 7 miles of WWTPs or sewage effluent

discharges providing a point source that discharged into a receiving stream, or one of its tributaries, in the beach watershed. All beach sites were selected so that they had sufficient variability in water quality so that the relationship between water quality and illness could be investigated without a control beach. Each beach also had to be generally compliant with local or

state water quality guidelines. Beach site locations and descriptions are shown in Figure 4.1 and Table 4.1.

3. Data collection: Health surveys

Trained interviewers approached all beach visitors as they arrived between 11:00 AM and 5:00 PM, and were enrolled if they provided verbal informed consent. Each participant

completed three surveys, with an adult (≥18 years old) answering questions for other household members. At baseline, each participant completed an enrollment questionnaire about illnesses in the three days prior to their beach visit. Upon departure, participants completed a beach

questionnaire about beach activities, water exposure (extent, time, duration and location), presence of underlying acute and chronic health conditions (including allergies), food and drink consumption, animal contact in the past 48 h, contact with sick persons in the past 48 h, other swimming in the past week, and demographics. A low-cost incentive was offered after

completion of the beach questionnaire. Follow-up telephone interviews were conducted 10–12 days after the beach interview to collect information about the enteric and non-enteric illnesses (gastrointestinal, diarrhea, upper respiratory, skin rash, ear, eye, urinary tract infection) each beachgoer experienced since the beach visit, burdens experienced as a result of illness (e.g. missed days of work), and other swimming or water related activities, contact with animals, and consumption of high-risk foods since the beach visit. Interviews were conducted on weekends and holidays between May and September. Because of the acute nature and short duration of the enteric and non-enteric symptoms and illnesses in this study, repeated enrollment of participants was allowed. However, participants were ineligible if they had already completed the study in

the previous 28 days, were unaccompanied minors (<18 years), or did not speak English or Spanish.

4. Data collection: Outcome assessments

In a telephone interview 10-12 days following beach exposure, interviewers asked beachgoers to self-report if they had experienced any gastrointestinal illness, diarrhea, upper respiratory illness, eye ailments, earache, skin rash or urinary tract infection since their beach interview. The time period accounts for pathogens with longer incubation times, such as

Cryptosporidium spp., a common waterborne pathogen. These heath outcomes are consistent with previous reports investigating the association between fecal indicator organisms and illness, to facilitate comparison (56,57,62,65,98,99). Responses to questions about symptoms or illness could take the form of Yes, No, Refused, or Don't know.

“Gastrointestinal illness” (GI illness) refers to any of the following: diarrhea (≥3 loose stools in a 24-hour period); vomiting; nausea and stomachache; or nausea or stomachache and interference with regular activities (missed time from work/regular activities due to illness).

‘‘Respiratory illness’’ refers to any two of the following: sore throat, cough, runny nose, cold, or fever.

‘‘Rash’’ refers to a rash or itchy skin.

‘‘Eye ailments’’ refers to eye infection or watery eye.

‘‘Earache’’ refers to earache, ear infection, or runny ears.

“Urinary tract infection” (UTI) refers to urinary tract infection or burning sensation when urinating.

Diarrhea was also be considered as a stand-alone outcome because it is frequently used as a definition of gastroenteritis in population-based surveillance e.g.(100,101).

Participants ill within the three days prior to their beach visit were excluded from analysis of the health outcome related to their baseline symptoms, but were eligible to be included in analyses of other outcomes.