Oral Presentation 12th Australasian Virology Society Meeting 2024

Phylogenomics of Murray Valley encephalitis genotypes of the 2023 Australian outbreak (#104)

Jackie E Mahar 1 , John-Sebastian Eden 2 3 , Matthew J Neave 1 , Patrick Mileto 1 , Annaleise R Howard-Jones 2 4 5 , Rebecca Rockett 2 6 , Tanya Golubchik 2 6 , Chuan K Lim 7 , Leon Caly 7 , Ammar Aziz 7 , Chisha Sikazwe 8 9 , Avram Levy 8 9 , Peter T Mee 10 , Natasha D Brohier 10 , Andrew Vickers 11 , Michaela Hobby 11 , Vicki Burns 11 , Alyssa Pyke 12 , John S Mackenzie 13 , Ashmita Thomas 14 , Kate Proudmore 15 , Grace Butel-Simoes 7 , Kevin Freeman 15 , Justin Ellem 4 , Nina Kurucz 16 , Kirsten Smyth 12 , Amy Jennison 17 , Peter Moore 12 , Rose Wright 18 , Rebecca Feldman 19 , Dominic E Dwyer 2 4 6 , Matthew V O’Sullivan 2 4 6 , Andrew A Mahony 14 20 , Morgyn S Warner 21 22 , Lito E Papanicolas 21 , Sanmarie Schlebusch 23 , Robert Baird 15 , David Smith 8 24 , David Speers 8 , Bart J Currie 25 , Jen Kok 2 4 6 , David T Williams 1
  1. Commonwealth Scientific and Industrial Research Organisation, East Geelong, VIC, Australia
  2. Sydney Institute for Infectious Diseases, The University of Sydney, Sydney, NSW, Australia
  3. Westmead Institute for Medical Research, Centre for Virus Research, Westmead, NSW, Australia
  4. Centre for Infectious Diseases & Microbiology Laboratory Services, New South Wales Health Pathology – Institute of Clinical Pathology & Medical Research, Westmead Hospital, Westmead, NSW, Australia
  5. Centre for Infectious Diseases & Microbiology Laboratory Services, New South Wales Health Pathology – Institute of Clinical Pathology & Medical Research, Westmead Hospital, Westmead, NSW, Australia
  6. Centre for Infectious Diseases and Microbiology – Public Health, Westmead Hospital, Westmead, NSW, Australia
  7. Victorian Infectious Diseases Reference Laboratory, The Royal Melbourne Hospital, at the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, Australia
  8. Department of Microbiology, North West Network, PathWest Laboratory Medicine Western Australia, QEII Medical Centre, Nedlands, WA, Australia
  9. School of Biomedical Sciences, University of Western Australia, Perth, WA, Australia
  10. Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, VIC, Australia
  11. Health Protection, Public Health Division, SA Health, Adelaide, SA, Australia
  12. Public Health Virology, Public and Environmental Health Reference Laboratories, Department of Health, Queensland Government, Coopers Plains, QLD, Australia
  13. Faculty of Health Sciences, Curtin University, Bentley, WA, Australia
  14. Department of Infectious Diseases and Immunology, Austin Health, Heidelberg, VIC, Australia
  15. Territory Pathology, Royal Darwin Hospital. Department of Microbiology, Tiwi, NT, Australia
  16. Centre for Disease Control, Public Health Division, NT Health, Tiwi, NT, Australia
  17. Public and Environmental Health, Pathology Queensland, Queensland Health, Coopers Plains, QLD, Australia
  18. Office of Health Protection and Response, Australian Government Department of Health, Canberra, ACT, Australia
  19. Communicable Diseases Section, Health Protection Branch, Victorian Department of Health, Melbourne, VIC, Australia
  20. Infectious Diseases Unit, Bendigo Health, Bendigo, VIC, Australia
  21. Microbiology & Infectious Diseases Directorate, SA Pathology, Royal Adelaide Hospital, Adelaide, SA, Australia
  22. School of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia
  23. Public and Environmental Health Reference Laboratories, Queensland Health, Coopers Plains, QLD, Australia
  24. School of Medicine, University of Western Australia, Perth, WA, Australia
  25. Global and Tropical Health Division, Menzies School of Health Research Charles Darwin University, Infectious Diseases Department, Royal Darwin Hospital, Tiwi, NT, Australia

Murray Valley encephalitis virus (MVEV) is a mosquito-borne orthoflavivirus endemic to northern Australia and Papua New Guinea. MVEV circulates between mosquitoes and waterbirds, while humans are dead-end hosts. Infection in humans is usually asymptomatic, however a small number of cases are symptomatic with a proportion resulting in mortality. There is currently no treatment or vaccine and its control relies on public health warnings and mosquito management. MVEV was first isolated in 1951 during a large outbreak in southeastern Australia and has since caused sporadic cases and epidemics in northern Australia. Two additional large national outbreaks occurred in 1974, and 2011. In 2023, a fourth nation-wide outbreak of MVEV occurred in Australia, with 27 encephalitic cases in humans, the largest number of cases since 1974. We conducted a genomic analysis of the 2023 outbreak MVEVs to characterize the genotypes involved and determine the extent and direction of spread. We sequenced the MVEV genomes from 5 clinical cases (from NT, VIC) and more than 40 mosquito pools from VIC, NSW, NT, WA, SA and QLD using Illumina sequencing. We determined that two genotypes, G1A and G2 were involved in the 2023 outbreak. G2 was only detected in the northern endemic regions in WA and the NT, consistent with previous reports. Conversely, despite previously being detected only in northwest Australia, G1A was found to have spread into southern and eastern areas, including QLD, NSW, VIC, and SA. In the genome phylogeny, we found that the human-derived sequences clustered amongst the mosquito-derived sequences, as expected for a mosquito-borne virus, and clustering within genotypes did not correlate with geography. The 2023 MVEV outbreak was associated with La Niña climatic conditions, highlighting the impact of environmental factors on zoonotic diseases and the importance of One Health surveillance as climate events increase due to global warming.