Public health and economic costs of investigating a suspected outbreak of Legionnaires' disease

Epidemiology and direct health care costs of hospitalised legionellosis in New Zealand, 2000-2020

BACKGROUND

Legionellosis is a collective term used for disease caused by Legionella species which result in community and hospital acquired pneumonia worldwide. The aim of this analysis was to describe the epidemiology of legionellosis hospitalisations in Aotearoa New Zealand (NZ) over a 21-year period and quantify the health care costs.

METHOD

This study combined national legionellosis notification and hospital discharge data that were linked via the National Health Index (NHI) to provide a more complete dataset of hospitalised cases. The direct cost of hospital care was estimated by multiplying the diagnosis-related group cost-weight by the national price and inflating to 2020/2021 values.

RESULTS

There were 1479 records matched across notifications and discharge databases, including 990 with principal and 489 with additional diagnosis of legionellosis. Incidence rose to an average of 143 cases per annum for 2016-2020, a rate of 3·2/100,000. The median LOS was 6 days (IQR 4-13·5) with direct costs of $2·1 million per annum over that period. Rates were highest in those aged 65 years and above, male, and of European/Other ethnicity. Hospitalisations showed a peak in spring and summer.

CONCLUSION

The rate of hospitalised legionellosis in New Zealand rose from 2000 to 2015, largely reflecting improved diagnosis. This preventable disease results in substantial health care costs. Greater efforts are needed to identify and control sources of exposure. Surveillance could be improved by routine integration of notification and hospital discharge data.

Investigation of a cluster of Legionnaires' disease during the outbreak of coronavirus disease 2019 pandemic in northeastern Taiwan, June 2021

PURPOSE

To describe the investigation and intervention of a cluster of Legionnaires' disease detected during the outbreak of coronavirus disease 2019 (COVID-19) pandemic.

METHODS

From June 7 to 22, 2021, 15 cases in the neighborhood near our hospital were detected. Information about residence, workplace, hospital visit, and potential exposures was collected. Sampling and decontamination were performed for potential sources.

RESULTS

All 15 patients had pneumonia when visiting the emergency room with negative COVID-19 test results. Most patients were male (73.3%) with the mean age of 65.7 years. The most common comorbidities were diabetes mellitus (40.0%) and hypertension (40%). The most common symptom was fever (93.3%). Two (13.3%) patients needed mechanical ventilators. Fever subsided within 2 days of treatment for most cases (85.7%). Five cases had exposure history at our hospital, and the other 10 lived or worked in the area within 2 km of our hospital, mostly in buildings A and B. Water sampling was carried out for our hospital, buildings A and B; one water sample from a cooling tower in our hospital cultured positive for Legionella bacteria. Early testing and treatment for suspected cases were carried out for the outbreak, and all cases were discharged with pneumonia resolution.

CONCLUSION

This was a community outbreak of Legionnaires' disease near our hospital. COVID-19 tests were repeated frequently before testing for Legionnaires' disease during the COVID-19 pandemic. Early recognition of Legionnaires' disease and timely treatment improved outcome.

Environmental Investigation during Legionellosis Outbreak, Montérégie, Quebec, Canada, 2021

In August 2021, a legionellosis outbreak involving 7 persons occurred within a 500-meter radius in the Montérégie region of Québec, Canada. Near real-time modeling of wind direction along with epidemiologic and environmental investigations identified the possible source. Modeling wind direction could help identify likely Legionella pneumophila sources during legionellosis outbreaks.

Travel-associated cases of Legionnaires' disease in the United States, 2015-2016

BACKGROUND

Recent travel is associated with ~20% of reported Legionnaires' disease (LD) cases worldwide.

METHODS

We analyzed LD cases reported to the Centers for Disease Control and Prevention (CDC) during 2015-2016. Travel-associated cases met case criteria for confirmed LD in someone who spent ≥1 night away from home during the 10 days before symptom onset. Most analyses were limited to travel-associated, public accommodation stay (TAPAS) cases. We used reported travel dates to estimate the number of TAPAS cases acquired during travel.

RESULTS

Of 12,200 LD cases reported among U.S. residents, 12.3% were travel-associated; 8.7% were TAPAS. Median patient age for TAPAS cases was 61 years; 64.4% were male; 67.3% were white; 77.9% were non-Hispanic; 96.1% were hospitalized; 4.5% died. Among 887 TAPAS cases involving U.S. destinations, an estimated 29.8% were acquired during travel; 4.28 TAPAS cases were reported, and an estimated 1.10 TAPAS cases were acquired during travel, per 10,000,000 hotel room nights booked. Sixty-eight U.S. TAPAS clusters were detected.

CONCLUSIONS

While acquisition during travel accounted for a relatively small proportion of all LD cases, clusters of TAPAS cases were frequently detected. Prompt notification of these cases to CDC facilitates cluster detection and expedites intervention.

Environmental sources of community-acquired legionnaires' disease: A review

BACKGROUND

Most Legionnaires' disease in the US and abroad is community-acquired and believed to be sporadic, or non-outbreak associated. Most patients are exposed to numerous water sources, thus making it difficult to focus environmental investigations. Identifying known sources of sporadic community-acquired Legionnaires' disease will inform future sporadic Legionnaires' disease investigations as well as highlight directions for research. The objective is to summarize and rank sporadic Legionnaires' disease sources based on the level of linkage between the environmental source and cases.

METHODS

A PubMed search was conducted using the search terms legion* and (origins or source or transmission) and (sporadic or community-acquired). Studies of nosocomial and/or outbreak-associated disease were excluded from this review. Definite, probable, possible and suspect ranks were assigned to sources based on evidence of linkage to sporadic Legionnaires' disease.

RESULTS

The search yielded 196 articles and 47 articles were included in the final review after application of exclusion criteria. A total of 28 sources were identified. Of these, eight were assigned definite rank including residential potable water and car air-conditioner water leakage. Probable rank was assigned to five sources including solar-heated potable water and soil. Possible rank was assigned to nine sources including residential potable water and cooling towers. Suspect rank was assigned to 20 sources including large building water systems and cooling towers.

CONCLUSION

Residential potable water, large building water systems and car travel appear to contribute to a substantial proportion of sporadic Legionnaires' disease. Cooling towers are also a potentially significant source; however, definitive linkage to sporadic cases proves difficult. The sources of sporadic Legionnaires' disease cannot be definitively identified for most cases.

Lessons Learned From Implementing an Incident Command System During a Local Multiagency Response to a Legionnaires' Disease Cluster in Sydney, NSW

The incident command system (ICS) provides a common structure to control and coordinate an emergency response, regardless of scale or predicted impact. The lessons learned from the application of an ICS for large infectious disease outbreaks are documented. However, there is scant evidence on the application of an ICS to manage a local multiagency response to a disease cluster with environmental health risks. The Sydney Local Health District Public Health Unit (PHU) in New South Wales, Australia, was notified of 5 cases of Legionnaires' disease during 2 weeks in May 2016. This unusual incident triggered a multiagency investigation involving an ICS with staff from the PHU, 3 local councils, and the state health department to help prevent any further public health risk. The early and judicious use of ICS enabled a timely and effective response by supporting clear communication lines between the incident controller and field staff. The field team was key in preventing any ongoing public health risk through inspection, sampling, testing, and management of water systems identified to be at-risk for transmission of legionella. Good working relationships between partner agencies and trust in the technical proficiency of environmental health staff aided in the effective management of the response. (Disaster Med Public Health Preparedness. 2018;12:539-542).

Eliminating Legionella by inhibiting BCL-XL to induce macrophage apoptosis

Human pathogenic Legionella replicate in alveolar macrophages and cause a potentially lethal form of pneumonia known as Legionnaires' disease(1). Here, we have identified a host-directed therapeutic approach to eliminate intracellular Legionella infections. We demonstrate that the genetic deletion, or pharmacological inhibition, of the host cell pro-survival protein BCL-XL induces intrinsic apoptosis of macrophages infected with virulent Legionella strains, thereby abrogating Legionella replication. BCL-XL is essential for the survival of Legionella-infected macrophages due to bacterial inhibition of host-cell protein synthesis, resulting in reduced levels of the short-lived, related BCL-2 pro-survival family member, MCL-1. Consequently, a single dose of a BCL-XL-targeted BH3-mimetic therapy, or myeloid cell-restricted deletion of BCL-XL, limits Legionella replication and prevents lethal lung infections in mice. These results indicate that repurposing BH3-mimetic compounds, originally developed to induce cancer cell apoptosis, may have efficacy in treating Legionnaires' and other diseases caused by intracellular microbes.

Molecular diagnostics and the public health management of legionellosis

In 2009-2010, we investigated four legionella cases notified over an 8-month period in two adjacent villages in South East England. Molecular techniques enabled us to conclude that three of the cases had distinct infections. The absence of an adequate respiratory sample in one case necessitated epidemiological investigations to exclude a potential common environmental source of further infections. One of the cases had spent a part of their incubation period in a country in South East Asia. DNA-sequence-based typing of their isolate showed it to be of the Legionella pneumophila serogroup 1 (LP1) DNA-sequence type (ST) 481. Intriguingly, the only other two ST 481 isolates in the European Working Group for Legionella Infections database were among Dutch travellers to the same country in 2003 and 2006. This case makes clear the value of molecular diagnostics and the importance of obtaining adequate clinical specimens. The potential future uses for typing data are discussed.

Investigation of outbreaks: epidemiology

Outbreaks of Legionnaires' disease create high levels of public anxiety and media interest and inevitably consume a great deal of public health resources. Investigations should begin as early as possible in order to rapidly identify suspected sources of infection, control the outbreak and prevent further cases occurring. The investigations should be coordinated by an outbreak control team who work collaboratively within local/national/international public health guidelines and with clear terms of reference. The actions carried out by epidemiologists when investigating community-, hospital-, or travel-associated outbreaks are comprehensively outlined in this chapter. The microbiological and environmental actions that complement this work are discussed in the accompanying chapters.