Analysis of Confirmed Leptospirosis Cases in Hawai'i Identifies Spatial and Environmental Patterns of Incidence

Leptospirosis is a neglected zoonotic disease caused by pathogenic Leptospira species, and it is one of the leading causes of zoonotic bacterial infections globally. It is routinely underdiagnosed or misdiagnosed as other febrile infections, like dengue or malaria. Hawai'i has consistently had one of the highest rates of leptospirosis in the United States. Here, we present the trends associated with cases of confirmed leptospirosis that were acquired in the state of Hawai'i between 2012 and 2024. County-level analysis shows consistency with previously observed spatial trends, identifying higher case rates on the islands of Kaua'i and Hawai'i ranging from 17.74 to 30.90 cases per 100,000 population. To increase spatial resolution, cases were analyzed at the Moku level (i.e., district), identifying localized rates up to 244.78 cases per 100,000 population. This analysis identified that the northeastern region of Maui has the highest case rate in Hawai'i, which has the highest case rate of all states. The northeastern coasts of each island tend to have higher rates of leptospirosis that also correlate with higher annual rainfall. Serological analysis identified that the dominant serogroups in human disease were Australis and Icterohaemorrhagiae. The main infecting Leptospira serovars were Bratislava, Icterohaemorrhagiae, Georgia, Canicola, and Australis. Dominant infecting serovars were associated with infections throughout the state, except in the case of Canicola, which was localized to the islands of Maui and Hawai'i. Overall, this work identified regions of higher human leptospirosis incidence throughout the Hawaiian Islands, correlating clinical incidence with precipitation and serovar reactivity across the state.