state epidemiology sta interviewed LD cases using the standard questionnaire with a supple- mental LD form and developed a line list that included information pertinent to the investi- gation: demographics, home address, symptom onset date, UAT results date, interview status, Legionella culture status, and local travel his- tory. Sta members from the Bureau of Water Supply Protection were notified and given a summary of the outbreak. In total, 25 potential cases were evaluated during the investigation (Table 1). Potential cases were ruled out based on negative UAT results, interviews, and travel history. By 2021, 17 cases were associated with the outbreak (Table 1) and 74 total environ- mental samples were collected (Table 2). Based on the interview data, home addresses of all confirmed cases were plot- ted, and a centroid (i.e., geometric center) of the combined case travel area was gener- ated using ArcGIS 10.8. Using this centroid, a 1-mi radius map was generated that displayed compliant and noncompliant cooling towers (via the state cooling tower registry). Initially, this map contained seven noncompliant and four compliant towers within a 1-mi radius of the four initial cases. This map was distrib- uted to NYSDOH and CCHD sta . Cooling towers that were noncompliant were given priority for contact. When the majority of the noncompliant cooling towers within the 1-mi radius did not appear to be problematic, an investigation of compliant and out-of-service cooling towers within the geo- graphic area was conducted. These towers were visited by NYSDOH and CCHD sta to review maintenance and management plans, check records, and collect samples. A total of seven towers were investigated and sampled during the first visit. A total of 11 towers were sampled over the course of the investigation including cooling tower E, which was ultimately identi- fied as the likely exposure source for numerous cases. Cooling tower E was one of three year- round towers located on the grounds of a heat treatment and processing plant located within 2 mi of residences of the four LD cases. In 2019, a Chemung County wastewa- ter treatment plant was sampled to continue evaluating potential environmental exposures. Outbreaks related to such plants have been reported previously in the literature (Caicedo et al., 2019). Sampling points were determined according to which part in the process was most likely to harbor Legionella and cause it to
TABLE 1
Cases Investigated for Legionnaires’ Disease in New York During the 2019–2021 Outbreak
Test Result
# of Cases Investigated
# of Cases Related to the Outbreak
# of Cases Ruled Out*
UAT+
Lp1 isolated, genetically related** Lp1 isolated, not genetically related** No Legionella isolated ** No sputum collected Sputum tested negative
5
5
0
4
2
2
3
2 8 0
1 2 3 8
10
UAT- Total
3
25
17
* Cases were ruled out due to travel history or a UAT- result. ** Isolates were from collected sputum samples. Note. Lp = Legionella pneumophila ; UAT+ = urine antigen test positive; UAT- = urine antigen test negative.
TABLE 2
Type of Environmental Sample Collected and Analysis Performed for Legionella in New York During the 2019–2021 Outbreak
Sample Type
# of Samples Collected
Analysis Method**
Standard Culture (ISO 11731)
Standard qPCR
Rapid qPCR
Wastewater treatment plant
3
3
3
0
Cooling tower basin Cooling tower swab
22 10 29
22 10 29
13
16
0
3 9 0 0 2
Residence
25
Hot tub water Hot tub swab
2 3 5
2 3 5
1 2 1
Other nonpotable water source*
Total
74
74
45
30
* Noncooling tower swab samples (e.g., decorative fountains, baseball field irrigation system). ** Multiple methods of analysis could have been performed on each sample. Note. qPCR = quantitative polymerase chain reaction.
Methods
whole genome sequencing of clinical and environmental samples. The WC-EBL was responsible for analyzing environmental samples. The extent and size of the outbreak, coupled with the relatively high number of sputum samples, made finding the potential exposure source a priority.
Environmental Investigation Steps An investigation was initiated after four LD cases in the area were reported on August 21, 2019, with symptom onset dates ranging from August 1, 2019, to August 18, 2019. Local and
17
May 2024 • Journal of Environmental Health
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