Evaluation of Hospitalizations for Tick-Borne Diseases in the United States from 2002 to 2021

Tick-borne diseases (TBDs) are a growing public health concern in the United States. This study analyzed 261,630 weighted hospitalizations from the Healthcare Cost and Utilization Project (HCUP) Nationwide Inpatient Sample (NIS) database between 2002 and 2021 to evaluate trends, coinfections, demographic disparities, and financial impacts. Lyme disease was the most common cause, accounting for 65% of hospitalizations (171,328 admissions), followed by ehrlichiosis/anaplasmosis (46,446), babesiosis (18,057), rickettsial diseases (16,412), tularemia (2428), and other TBDs (19,435). Hospitalizations increased 2.5-fold over the study period, with the Northeast region bearing 52.9% of the burden and peaking in July. Males (53.9%), Caucasians (81.4%), and residents of higher-income zip codes were predominant, though rickettsial diseases showed elevated Hispanic representation (18.4%). Coinfections were common, with 35.8% of babesiosis and 15.6% of ehrlichiosis/anaplasmosis cases involving another TBD, suggesting that routine testing may be warranted. Median hospital charges rose from USD 9433 in 2002 to USD 35,161 in 2021, totaling USD 1.265 billion in 2021. In-hospital mortality was 1.1%, with the highest cause of mortality being babesiosis (2.06%). Future areas for research include characterizing the burden of disease in an outpatient setting, understanding the causes of racial disparities in hospitalizations, and testing strategies to identify coinfection.