July 2022

Highlights: Emerging Infectious Diseases, Vol. 28, No. 7, July 2022

The articles of interest summarized below will appear in the July 2022 issue of Emerging Infectious Diseases, CDC’s monthly peer-reviewed public health journal. This issue will feature parasitic infections. The articles are embargoed until June 15, 2022, at noon Eastern time.

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1. Deaths from Tick-Borne Encephalitis, Sweden
   Tick-borne encephalitis (TBE) is a viral infection transmitted to people usually by the bite of an infected tick and is endemic in parts of Asia and Europe, including Sweden. On rare occasions, people also have been infected through eating or drinking raw milk products from infected goats, sheep or cows. TBE typically begins with fever and flu-like illness but can progress to a second phase with neurological symptoms of varying severity. The overall case-fatality rate in TBE in Europe is below 1 percent. Older adults who are infected are more at risk for severe disease and death. To investigate the relative contribution of TBE to the overall death rate in Sweden, researchers calculated a standardized mortality ratio (likelihood of death for a specific population compared with a reference population) for persons with TBE during 2004–2017. TBE patients in Sweden were 4 times more likely to die within 3 months after diagnosis than those in the control population (same age, sex, and county of residence). Risk for death was highest among TBE patients older than 60. There were no reported fatal cases in patients under the age of 40. Those findings demonstrate the need to increase TBE vaccination efforts in Sweden, especially for older persons.
   
   Contact: Jonas Klingström, Center for Infectious Medicine, Stockholm, Sweden; email: jonas.klingstrom@ki.se
   
   Note: A vaccine for TBE has recently been licensed in the United States and is recommended for some travelers visiting endemic areas in parts Europe and Asia.
2. One Health Genomic Analysis of Extended-Spectrum β-Lactamase‒Producing Salmonella enterica, Canada, 2012‒2016, Amrita Bharat et al.
   Extended-spectrum β-lactamases (ESBLs) are enzymes that are found inside some bacteria. ESBLs confer resistance to extended-spectrum cephalosporins, which are a major class of antimicrobial drugs. Researchers used genetic analysis to investigate whether domestic food animals, meat products, and pets were potentially infecting humans with ESBL-producing Salmonella in Canada. Among 30,303 Salmonella isolates tested during 2012–2016, the researchers detected 95 ESBL-producers. ESBL types were mostly different between humans and animals or meat, but two types were found in both sources. The most common ESBL-producer in humans was Salmonella Infantis carrying the bla_CTX-M-65 gene, which has since emerged in poultry in other countries. The study also detected a few instances of similar isolates and plasmids, suggesting that domestic animals and retail meat might have been minor sources of ESBL-producing Salmonella that infected humans in Canada during 2012–2016. Although levels of ESBL-producing Salmonella detected in this study were low, continued surveillance is essential, given that extended-spectrum cephalosporins are a major treatment option for serious or invasive Salmonella infections. Like ESBL-producing Escherichia coli and Klebsiella pneumoniae, ESBL-producing Salmonella could become a healthcare challenge because treatment options are limited.
   
   Contact: Media Relations, Public Health Agency of Canada, email: media@hc-sc.gc.ca, phone: 613-957-2983