Leptospirosis in Hawai'i: A Retrospective Study within a Health Care System, 2010-2021

Leptospirosis is a worldwide zoonotic disease with diverse clinical manifestations, ranging from mild flu-like symptoms to a life-threatening illness. It is often misdiagnosed or underreported due to the non-specific and overlapping clinical presentations with other febrile illnesses. Hawai'i has the highest incidence of leptospirosis in the United States, but there is a paucity of data regarding recent incidence and the current leptospirosis trends in Hawai'i. The objective of this study was to determine the epidemiology of patients with leptospirosis at one of the largest health care systems in Hawai'i and to identify risk factors associated with the severe illness. A retrospective study was conducted on patients with clinically suspected or confirmed leptospirosis diagnosis from 2010-2021. Of the 164 patients identified during the timeframe, 81 were outpatients with mild illness and 83 were inpatients exhibiting a more severe infection. Patients with the severe infection had a higher frequency of abnormal laboratory tests, including abnormal electrolytes, kidney and liver function tests. This group was more likely to suffer from acute kidney disease, sepsis, and rhabdomyolysis. More cases of leptospirosis were observed in the drier summer months of Hawai'i, and there were more cases in the areas with heavier rainfall on the island of Kaua'i. Risk factors for severe leptospirosis included being Native Hawaiian/Pacific Islander and elevated body mass index. Further studies on leptospirosis may reveal how patients with the above risk factors may benefit from early detection and treatment, potentially leading to reduced disease severity, and decreased hospitalization length.