Published online by Cambridge University Press: 04 May 2016
Seasonal variation is a characteristic of many infectious diseases, but relatively little is known about determinants thereof. We studied the impact of place of acquisition and patient characteristics on seasonal variation of bacteremia caused by the 3 most common pathogens.
Seasonal variation analysis.
In 3 Danish health regions (2.3 million total inhabitants), patients with bacteremia were identified from 2000 through 2011 using information from laboratory information systems. Analyses were confined to Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae. Additional data were obtained from the Danish National Hospital Registry for the construction of admission histories and calculation of the Charlson comorbidity index (CCI). Bacteremias were categorized as community acquired, healthcare associated (HCA), and hospital acquired. We defined multiple subgroups by combining the following characteristics: species, acquisition, age group, gender, CCI level, and location of infection. Assuming a sinusoidal model, seasonal variation was assessed by the peak-to-trough (PTT) ratio with a 95% confidence interval (CI).
In total, we included 16,006 E. coli, 6,924 S. aureus, and 4,884 S. pneumoniae bacteremia cases. For E. coli, the seasonal variation was highest for community-acquired cases (PTT ratio, 1.24; 95% CI, 1.17–1.32), was diminished for HCA (PTT ratio, 1.14; 95% CI, 1.04–1.25), and was missing for hospital-acquired cases. No seasonal variation was observed for S. aureus. S. pneumoniae showed high seasonal variation, which did not differ according to acquisition (overall PTT ratio, 3.42; 95% CI, 3.10–3.83).
Seasonal variation was mainly related to the species although the place of acquisition was important for E. coli.
Infect Control Hosp Epidemiol 2016;37:946–953
PREVIOUS PRESENTATION. Gradel KO, Nielsen SL, Pedersen C, Knudsen JD, Østergaard C, Arpi M, Jensen TG, Kolmos HJ, Søgaard M, Lassen AT presented these data in part as Poster P0012, “Seasonal variation in blood stream infection in relation to bacterial agents and acquisition” at the 25th European Congress of Clinical Microbiology and Infectious Diseases, April 25–28, 2015, in Copenhagen, Denmark.