Environmental Investigation of a Campylobacteriosis Outbreak Among Wedding Attendees — York County, Pennsylvania, 2025

Investigation and Outcomes

Survey of Event Attendees

On June 30, PDOH sent a link to an online questionnaire to all wedding attendees to identify additional cases and characterize exposures. Because some attendees shared email addresses, the exact number of attendees who received the questionnaire could not be determined; however, 46 responses were received. Among these, 15 (33%) persons reported gastrointestinal illness 1–10 days after the event; however, no specific food item associated with illness was identified.

Use of On-Site Spring Water During the Event and Inspection of the Spring

The venue manager reported that the site normally relied on vendors to supply potable water and ice. However, after the vendor’s bottled water supply was exhausted during the event, employees of the vendor began drawing water from a kitchen tap connected to an on-site spring for food preparation and beverage service; no signage identified the water as nonpotable.

An onsite inspection by PDOH and PDA officials identified substantial deficiencies at the spring, including 1) a broken springhouse roof allowing entry of debris and animal feces (Figure), 2) a nonfunctional ultraviolet treatment unit (inoperable for ≥2 months), 3) evidence of animal activity, and 4) proximity of the spring to a chicken coop and an area occupied by horses.

Testing of Water Samples

On July 9, PDOH and PDA officials collected paired large-volume (100-L) ultrafiltered and (500-mL) grab samples^† from the spring and the kitchen tap (1); point-of-use ultraviolet filters^§ had been installed in the kitchen tap after the wedding but before sample collection. CDC’s Environmental Microbiology and Engineering Laboratory analyzed samples for Campylobacter spp. (2), culturable fecal indicator bacteria (total coliforms and Escherichia coli), and microbial source tracking^¶ molecular markers targeting fecal contamination from birds and ruminants (3,4), potential reservoirs of Campylobacter organisms present on the property.

Culturable Campylobacter organisms were not recovered from any sample, but Campylobacter DNA was detected in both spring and tap water. Fecal indicator bacteria were markedly elevated in spring water (total coliforms >2,419.6 most probable number [MPN]/100 mL; E. coli 547.5 MPN/100 mL)** but undetectable at the tap, suggesting that point-of-use treatment reduced but did not eliminate detectable Campylobacter DNA. Source tracking markers for birds and ruminants were not detected at either site, leaving the source or sources of fecal contamination undetermined.

Preliminary Conclusions and Actions

Epidemiologic linkage of illness to spring-water consumption, environmental deficiencies at the spring, and detection of Campylobacter DNA and fecal indicator bacteria in the spring water support untreated spring water as the most likely outbreak source. Absence of culturable pathogens does not rule out prior contamination, because Campylobacter organisms can enter a viable but nonculturable state (5), and sampling occurred after symptom onset. After the investigation, the venue installed two point-of-use water filters, repaired the springhouse roof, and posted signage identifying water from spring-fed taps as nonpotable. State officials recommended that the venue improve communication with external vendors to prevent future use of the nonpotable water source for food preparation and drinking.

Private springs are largely unregulated in the United States, and, in the absence of visible contamination, users might assume such water is safe. These findings suggest that timely environmental testing paired with epidemiologic investigation could improve source attribution and guide the development and implementation of remediation efforts at venues serving the public. Routine inspection and maintenance of untreated private water sources might reduce the risk for waterborne outbreaks.