Prevalence of Barmah Forest Virus, Chikungunya Virus and Ross River Virus Antibodies among Papua New Guinea Military Personnel before 2019 †

Barmah Forest virus (BFV), Chikungunya virus (CHIKV) and Ross River virus (RRV) belong to the Alphavirus genus of the family Togaviridae. All three virus infections have been reported in Papua New Guinea (PNG) previously, but the exact prevalence and distribution of these three alphaviruses in PNG has not been established. Sera collected from 204 PNG Military Personnel (PNGMP) study participants in April 2019 was tested for the presence of anti-BFV, anti-CHIKV and anti-RRV immunoglobulin G (IgG) antibodies using commercially available enzyme-linked immunosorbent assay (ELISA) IgG detection kits, as well as for specific neutralizing antibodies (NAb) against individual viruses. Overall, sero-positivity of the sera was anti-BFV IgG 12.3% (25/204), anti-BFV NAb 8.3% (17/204); anti-CHIKV IgG 47.1% (96/204), anti-CHIKV NAb 34.8% (71/204); and anti-RRV IgG 93.1% (190/204), anti-RRV NAb 56.4% (115/204), respectively. Of the 137/204 participants that were Nab-positive for at least one virus, we identified 4 BFV, 40 CHIKV and 73 RRV single infections, and 9 RRV+CHIKV and 11 BFV+RRV double infections. The lower proportion of NAb sero-positive compared to the ELISA IgG sero-positive assay samples suggests that the currently available commercial ELISA detection kits for these three alphaviruses may not be suitable for diagnostic/surveillance purposes in endemic areas such as PNG, due to serological cross-reactivity among these three alphaviruses. Laboratory testing using known positive control sera indicated no cross-neutralization between BFV and RRV; however, some RRV or BFV single infection human sera demonstrated low-level cross-neutralization against CHIKV (the ratio of RRV/CHIKV NAb titers or BFV/CHIKV ≥ 4). Our preliminary results indicate that the majority of PNGMP have previously been exposed to RRV, with mild exposure to CHIKV and low-level exposure to BFV, suggesting that multiple alphaviruses have been circulating among PNGMP. The transmission landscapes of these three alphaviruses across PNG should be prioritized for further investigation, including identification of specific vectors and hosts that mediate human spillover in order to mitigate future outbreaks. Ongoing education regarding precautionary and protective measures are needed to better protect individuals who travel to PNG.