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Infectious diseases

Infectious diseases Medical education 4 September 2023 Open Access

Breakthrough mpox despite two‐dose vaccination

Clinicians should be aware of the possibility of breakthrough infection in patients with epidemiological risk factors and a characteristic vesiculopustular rash, irrespective of a history of previous vaccination

Madhara N Weerasinghe · Catriona Ooi · George Kotsiou · Vincent J Cornelisse · Arran Painter · Madhara N Weerasinghe · Catriona Ooi · George Kotsiou · Vincent J Cornelisse · Arran Painter

Mja2 52076
Infectious diseases Letters 3 July 2023 Free

Early detection of Murray Valley encephalitis virus activity in Victoria using mosquito surveillance

To the Editor: The flavivirus Murray Valley encephalitis virus (MVEV) was isolated in 1951 from the brain tissue of fatal cases of encephalitis.1 Subsequent work by Australian investigators established MVEV as the likely aetiological pathogen of the severe encephalitis “Australian X disease”.1 MVEV is enzootic in northern Western Australia and the Northern Territory, resulting in sporadic human cases.2 In south‐east Australia, however, MVEV activity can be absent for decades only to reappear with significant human outbreaks. The three most recent outbreaks in Australia were in 1951 (45 cases), 1974 (58 cases) and 2011 (17 cases).1,2,3 The case fatality rate is about 18% in hospitalised patients, reflecting the severity of disease.4 Since 1974, Victoria has employed vertebrate and invertebrate surveillance methods to detect MVEV activity before human cases.5 Until 2021, sentinel chicken flocks were placed along the Murray River and tested weekly for MVEV seroconversion during the mosquito season, which runs from November to April. The most recent seroconversions were in 2011, along the Murray River, in Greater Bendigo, and in Greater Shepparton.6 This testing strategy was limited by biological and logistic delays, diminishing the system as an early warning tool. In 2021, sentinel chickens were retired, with flavivirus testing combined into the long‐standing alphavirus mosquito trapping program when polymerase chain reaction (PCR) assays replaced labour‐intensive and insensitive cell culture methods.7 For the 2022–2023 mosquito season, in the setting of Japanese encephalitis virus activity and historic floods, the Victorian Department of Health supported 15 councils to trap mosquitoes as part of the Victorian Arbovirus Disease Control Program (VADCP). Trapped mosquitoes were pooled and submitted for PCR testing. The size and composition of these varied depending on the number of collected mosquitoes, with a preference for analysis of speciated mosquitoes if possible. Detections were confirmed with sequencing at a reference laboratory. As of 23 January 2023, we have detected MVEV in 14 mosquito traps across four local government areas (Box). The positioning and density of the traps are influenced by proximity to population centres and resource considerations, which may influence the likelihood of virus detection in different localities. The first detection was in mosquitoes collected on 4 January 2023. New South Wales and South Australia have also reported MVEV detections in multiple locations. Subsequently, on 17 February 2023 the first human case of MVEV infection in Victoria since 1974 was confirmed after lengthy investigation of a person with illness onset on 16 January 2023. This represents the first detections of MVEV in south‐east Australia in the 2022–2023 mosquito season, the first surveillance detections in Victoria since 2011, and the first confirmed human case in Victoria since 1974. The timing of these signals is notably earlier in the season than previous sentinel chicken seroconversions, which occurred in February 2011, supporting mosquito PCR testing as a rapid surveillance tool. This difference in timing may, however, be explained by inter‐year environmental or sampling factors, and a controlled comparison between mosquito and sentinel chicken surveillance, in the context of subsequent human cases, is required to demonstrate the most useful surveillance tool. Nonetheless, the presence of virus and capable vectors suggests the risk for human infection is present, and, importantly, informs public health actions. MVEV in south‐east Australia is rare and the time between outbreaks is measured in decades. These early mosquito surveillance signals have preceded a human health event which has not occurred in Victoria since 1974. In the absence of an effective vaccine, prevention relies on vector control and health promotion, while case detection requires clinician awareness. Retrospectively, a serosurvey will be essential to measure the extent of human exposure during this period of MVEV activity. Finally, given our understanding of MVEV in Victoria is limited by a paucity of historical events to analyse, researchers should engage in this rare opportunity to study MVEV epidemiology and ecology. Box – Victorian local government areas (LGA) with the first 14 polymerase chain reaction (PCR) detections of Murray Valley encephalitis virus in trapped mosquitoes in 2023 (shaded in red). LGAs where surveillance was undertaken are outlined. The inset shows the Australian state of Victoria shaded‐in and the dates of mosquito collection and notification to the Department of Health * Greater Bendigo LGA.

Maxwell Braddick · Aidan Yuen · Rebecca Feldman · N Deborah Friedman

Mja2 51987
Infectious diseases Medical education 5 June 2023 Open Access

Locally acquired respiratory diphtheria in Australia

A 32-year-old woman from a remote Indigenous community in Far North Queensland presented to her local health clinic with a one-day history of odynophagia

Simon Smith · James Stewart · Joshua Hanson · Julian Harris · Fred JJ Chuang · Gavin Quail · Bryan Hawarden · Roshni Lad · Shannon McNee · Benjamin McCartney · Tonia Marquardt · Ian Wilson · Catherine Tacon · Bernard CS Whitfield

Mja2 51938

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