Revisiting the risk of introduction of Japanese encephalitis virus (JEV) into the United States – An updated semi-quantitative risk assessment

Authors: DIXON, ANDREA - Kansas State University; OLIVEIRA, ANA - University Of California, Davis; Cohnstaedt, Lee; Mitzel, Dana; Mire, Chad; CERNICCHIARO, NATALIA - Kansas State University

Submitted to: One Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2024
Publication Date: 8/17/2024
Citation: Dixon, A.L., Oliveira, A.R., Cohnstaedt, L.W., Mitzel, D.N., Mire, C.E., Cernicchiaro, N. 2024. Revisiting the risk of introduction of Japanese encephalitis virus (JEV) into the United States – An updated semi-quantitative risk assessment. One Health. 19. Article 100879. https://doi.org/10.1016/j.onehlt.2024.100879.
DOI: https://doi.org/10.1016/j.onehlt.2024.100879

Interpretive Summary: Japanese encephalitis virus (JEV) is associated with illness in humans and pigs. The virus has spread outside of southeast Asia and has been detected in Europe (2010), Africa (2016), and most recently mainland Australia (2021-2022). The introduction of JEV into the United States (US) is a public and animal health risk, but also a threat to the food supply. Understanding how and where the virus will be introduced, transmitted, and spread is required to optimally prepare the United States for a JEV introduction and allow the public health infrastructure to respond rather than react to an introduction. The past risk assessment was updated using an established semi-quantitative risk assessment tool (MINTRISK) to compare the risk of JEV introduction and impact in seven US regions. Risk of introduction was considered negligible for the Rocky Mountain, Alaska, and Hawaii regions and non-negligible in the Northeast, Midwest, South, and West regions. After introduction of the virus, it must establish, and the South had a very high risk for establishment given it has similar environments to the native range of the virus in Asia. Risk of establishment on the West coast was considered moderate and very low for the Northeast and Midwest regions. The work also identified the most likely source of introduction to be infected mosquito eggs and larvae introduced via imported used tires and plant goods, and infected adult mosquitoes via ships. The Southern United States will be the most likely area for introduction and establishment; therefore surveillance and response plans should be focused in this area. The West, Midwest, and Northeast should be prioritized for surveillance activities for early JEV detection. Surveillance should focus on infected mosquitoes carried on ships and goods arriving in these regions. More information is needed about feral pig and wild bird populations in and around ports, as well as evidence on wild wading birds such as cranes and storks which contribute to transmission in South Asia.

Technical Abstract: Japanese encephalitis virus (JEV) is associated with encephalitis in humans and reproductive and neurological illness in pigs. JEV continues spread outside its native distribution of southeast Asia, and has been identified in Europe (2010), Africa (2016), and most recently mainland Australia (2021-2022). The introduction of JEV into the United States (US) is a public health risk and could also impact animal health and the food supply. To efficiently and cost-effectively manage risk, a better understanding of how and where diseases will be introduced, transmitted, and spread is required. To achieve this objective, we updated our group’s previous qualitative risk assessment using an established semi-quantitative risk assessment tool (MINTRISK) to compare the risk of JEV introduction and impact in seven US regions. The rate of introduction from the current region of distribution was considered negligible for the Rocky Mountain, Alaska, and Hawaii regions. The Northeast, Midwest, South, and West regions had non-negligible rates of introduction. Infected mosquito eggs and larvae introduced via imported used tires and plant goods, and infected adult mosquitoes via ships had the highest median risk score for rate of introduction, which ranged from low to high. The overall risk estimate for the South was very high (95% CI = all within very high), moderate for the West (95% CI = very low to very high), and very low for the Northeast (95% CI = negligible to high) and Midwest (95% CI = negligible to moderate/high) regions. Based on this risk assessment, the US South should be prioritized for preparedness to mitigate the impact of a potential JEV introduction and the West, Midwest, and Northeast should be prioritized for surveillance activities for early JEV detection. Furthermore, for managing risk, efforts should be targeted towards infected mosquitoes carried on ships and goods arriving in these regions. More information is needed about feral pig and wild bird populations in and around ports, as well as evidence on non-ardeid wild bird transmission effectiveness to accurately estimate JEV transmission risk.