Potential high arbovirus exposure in INDOPACOM during U.S. service member deployment or exercises in Papua New Guinea.

Arboviruses pose a significant health threat to U.S. military personnel deployed in the U.S. Indo-Pacific Command (INDOPACOM) region. In 2023 we conducted a sero-epidemiological study to determine the arboviruses circulating in 185 Papua New Guinea military personnel (PNGMP), using the neutralizing antibody (NAb) assay. Overall, sero-positivity rates among the 185 PNGMP tested were: anti-Zika virus (ZIKV), 87% (n=161); anti-Japanese encephalitis virus (JEV), 62.2% (n=115); anti-Ross River virus (RRV), 44.3% (n=82); anti-Murray Valley encephalitis virus (MVEV), 39.5% (n=73); anti-chikungunya virus (CHIKV), 33.5% (n=62); anti-Barmah Forest virus (BFV), 10.8% (n=20); and anti-West Nile virus (WNV), 5.9% (n=11). The monotypic NAb sero-positivity rates for dengue virus (DENV) serotypes were: anti-DENV-1 94.6% (n=175), anti-DENV-2 93% (n=172), anti-DENV-3 95.1% (n=176), and anti-DENV-4 31.4% (n=57). These findings indicate that the majority of PNGMP had prior exposure to DENV and ZIKV, with a notable proportion exposed to CHIKV, RRV, JEV, and MVEV, and lower levels of exposure to BFV and WNV. Low or moderate prior exposure may leave individual PNGMP immunologically naïve and more susceptible to infection and disease upon first exposure. Furthermore, secondary DENV infections with a different serotype can increase risk of severe disease due to immune enhancement mechanisms such as antibody-dependent enhancement. Understanding these exposure patterns is crucial for assessing population risk and informing surveillance and prevention strategies. U.S. soldiers exercising or deploying to Papua New Guinea should adhere to strict preventive measures for minimizing mosquito bites and reducing their risk of arboviral infections. To our knowledge, this study provides the first comprehensive examination of arbovirus sero-positivity rates in Papua New Guinea military personnel (PNGMP) following the COVID-19 pandemic. After examining sero-positivity of 11 arboviruses, we found a majority of PNGMP with neutralizing antibodies (NAb) to dengue and Zika viruses, with some NAb to chikungunya, Japanese encephalitis, Ross River, and Murray Valley encephalitis viruses. Sero-prevalence to Barmah Forest and West Nile viruses was less common.