The shift in seasonality of legionellosis in the USA

Abstract

According to the Centers for Disease Control and Prevention (CDC), from 2000 to 2014, reported cases of legionellosis per 100 000 population increased by 300% in the USA, although reports on disease seasonality are inconsistent. Using two national databases, we assessed seasonal patterns of legionellosis in the USA. We created a monthly time series from 1993 to 2015 of reported cases of legionellosis from the CDC, and from 1997 to 2006 of medical claims of legionellosis-related hospitalisation in older adults from the Centers for Medicaid and Medicare Services (CMS). We split the study time interval into two segments (before and after 2003), and applied a Poisson harmonic regression model to each dataset and each segment. The time series of monthly counts exhibited a significant shift of seasonal peaks from mid-September (9.676 ± 0.164 months) before 2003 to mid-August (8.452 ± 0.042 months) after 2003, along with an alarming increase in the amplitude of seasonal peaks in both CDC and CMS data. The lowest monthly reported cases of legionellosis in 2015 (281) exceed the maximum value reported before 2003 (206). We also observed a discrepancy between CDC and CMS data, suggesting that not all cases of legionellosis diagnosed by hospital-based laboratories were reported to the CDC. Improved reporting of legionellosis is required to better inform the public and organise disease prevention.

Legionella Diversity and Spatiotemporal Variation in the Occurrence of Opportunistic Pathogens within a Large Building Water System

“…Two percent of biofilm samples (1/57) and 12% of bulk water samples (14/114) were culture-positive for Legionella of which 57% (8/14) were isolated during the winter; 21% (3/14) during the summer; 14% (2/14) during the fall; and 7% (1/14) during the spring. Legionnaires’ disease (LD) cases typically peak during the summer and fall seasons [ 34 , 35 ]. However, other epidemiological studies reported a winter peak for non-travel related cases [ 36 ] and no monthly or seasonal correlations for nosocomial-acquired [ 37 ] and community-acquired Legionella pneumonia cases [ 38 ].…”

Assessing Seasonality Variation with Harmonic Regression: Accommodations for Sharp Peaks

“…It is well known that majority of infections exhibit strong seasonal patterns in disease incidence or prevalence [3][4][5][6][7][8][9][10][11]. Our own work illustrate that infections caused by bacteria, like Vibrio cholerae [4] and Salmonella [6]; by protozoa, like Giardia and Cryptosporidium [12]; and viruses, like Influenza [13,14] and Rotavirus [15,16] have well pronounced seasonal patterns, specific for the location, pathogenic strains, and the size and socio-demographic composition of the affected populations.…”

“…This lofty goal implies ability to describe, quantify, and examine temporal patterns, which include increasing or declining trends, seasonal patterns, unusual spikes associated with outbreaks or disappearance of periodic episodes that mark disease eradication. These temporal characteristics are often explored in order to detect emerging trends in populations of concern, determine the success of intervention programs on a population level, and to forecast the future temporal behaviors [1][2][3]. The temporal analyses are also performed to better understand the effects of contributing factors to changes over time.…”

Trends in Legionnaires’ Disease-Associated Hospitalizations, United States, 2006–2010

“…This observation may lead to unreliable estimates of the LD-associated hospitalization burden in race-specific groups. Third, seasonality studies have shown that LD patterns typically demonstrate a summer spike, with an increased incidence occurring during the warmer, more humid months of June–September [ 4 ]. With NHDS data, however, we cannot ascertain the precise time and location of the acquisition of infection.…”