Cluster of Legionellosis Cases Associated with Manufacturing Process, South Carolina, USA, 2022

Abstract

Evolving technology and the development of new devices that can aerosolize water present a risk for new sources of Legionella bacteria growth and spread within industrial settings. We investigated a cluster of legionellosis among employees of a manufacturing facility in South Carolina, USA, and found 2 unique equipment sources of Legionella bacteria. The cluster of cases took place during August-November 2022; a total of 34 cases of legionellosis, including 15 hospitalizations and 2 deaths, were reported. Legionella pneumophila was isolated from 3 devices: 2 water jet cutters and 1 floor scrubber. L. pneumophila sequence type 36 was identified in environmental isolates and 1 patient specimen, indicating that those devices were the likely source of infection. Remediation was ultimately achieved through the development and implementation of a device-specific water management program. Manufacturing facilities that use aerosol-generating devices should consider maintaining updated Legionella water management programs to prevent Legionella bacterial infections.

Keywords: Legionella pneumophila; Legionnaires’ disease; South Carolina; United States; bacteria; legionellosis; manufacturing facilities; occupational health; respiratory infections; water.

Figure 1

Classification of cases associated with a cluster of legionellosis in a manufacturing facility in South Carolina, USA, 2022. LTFU was defined as failure to reach a patient after 3 attempts within 1 week. Cases were excluded if either the case definition criteria were not met or if the patient had a clinically compatible illness and documentation of an alternative etiology or positive test for COVID-19 or influenza. LD, Legionnaires’ disease; LTFU, lost to follow-up.

Figure 2

Epidemic curve of reported cases of legionellosis associated with a manufacturing facility and timeline of corrective actions for potential exposure sources, South Carolina, USA, 2022. Of 34 total cases, 10 were confirmed LD cases, 20 probable LD cases, and 4 probable Pontiac fever cases. Red bar on x axis indicates when the cooling towers, water jet cutters, the chiller, and floor scrubbers were all shut off on September 18, 2022. The floor scrubbers were remediated on October 3, 2022. Blue bars on the x axis indicate remedial treatment of remaining water-processing devices on September 22; October 3, 14, 16, 17, 21, 27, and 28; and November 1, 2022. Date of death for 1 patient with probable LD was used as the illness onset date because we were unable to obtain a symptom onset date. LD, Legionnaires’ disease.

Figure 3

Usual work location of employees with confirmed and probable legionellosis according to shift and proximity to water jet cutters at a manufacturing facility in South Carolina, USA, 2022. Stars without circles indicate first shift workers. Facility is ≈1 × 10⁶ square feet with a ceiling height of 40 feet. Rooftop cooling tower is the primary source of cooling for the building, and air is circulated with industrial ceiling fans throughout the facility. Air flow studies were not performed. Patients reported working in various locations during the 14 days before illness onset. Facility is open-air with 1 interior wall separating the office space from the manufacturing side. Gray lines indicate production lines. Work location information was missing for 8 patients because of investigator inability to identify the location on the map, the employee reported moving throughout the facility, or inability to collect the information from either the employee or company management. Floor scrubbers are not shown because they were used throughout the facility.