Heartland Virus in Humans and Ticks, Illinois, USA, 2018–2019

Holly C. Tuten; Kristen L. Burkhalter; Kylee R. Noel; Erica J. Hernandez; Seth Yates; Keith Wojnowski; John Hartleb; Samantha Debosik; April Holmes; Christopher M. Stone


Emerging Infectious Diseases. 2020;26(7):1548-1552. 

In This Article

Abstract and Introduction


In 2018, Heartland disease virus infected 2 persons in Illinois, USA. In 2019, ticks were collected at potential tick bite exposure locations and tested for Heartland and Bourbon viruses. A Heartland virus–positive pool of adult male Amblyomma americanum ticks was found at 2 locations, 439 km apart, suggesting widespread distribution in Illinois.


Heartland virus (HRTV), a phlebovirus in the order Bunyavirales, is an emerging zoonotic pathogen. In 2009, after 2 cases were identified in persons in Missouri, additional cases were subsequently reported from Kansas, Oklahoma, Arkansas, Missouri, Tennessee, Kentucky, Indiana, Georgia, and South Carolina. Disease onset was most often during April–September.[1] HRTV symptoms can initially resemble those of ehrlichiosis[2] and include fatigue, fever, leukopenia, and thrombocytopenia.[3] Human illness caused by HRTV infection often requires hospitalization and has resulted in death.[1]

After 2 persons infected with HRTV in northwestern Missouri reported having noticed attached ticks before symptom onset,[4] subsequent entomologic studies detected HRTV in nymphal Amblyomma americanum ticks. Laboratory studies confirmed the competence of A. americanum ticks for transmitting HRTV transstadially and horizontally.[5] This body of evidence led to the implication of A. americanum ticks as the putative vector of HRTV.[2,6] Serologic surveys of mammals and birds subsequently detected HRTV-specific neutralizing antibodies in a variety of mammals, including raccoons and white-tailed deer, suggesting that various medium- and large-sized mammals may serve as hosts.[3,7]

A. americanum ticks are vectors of public health concern because of their aggressive biting behavior, willingness to feed on humans, and abundance. Over the past century, their distribution range has expanded northward,[8] and population establishment continues to increase because of climate change.[9] Habitat suitability models have suggested that this species' fundamental niche should reach the center of Illinois[10] or eventually encompass the state entirely.[9]

In July 2018, a Kankakee County, Illinois, resident (case-patient 1) reported having incurred multiple tick bites while camping on private residential property. The patient was hospitalized with fever, headache, myalgia, nausea, diarrhea, and a diffuse maculopapular rash. In September 2018, a Williamson County, Illinois, resident (case-patient 2) noticed tick bites while staying at a campground near home. The patient was hospitalized with fever, headache, myalgia, fatigue, decreased appetite, nausea, and diarrhea. The Centers for Disease Control and Prevention (CDC) confirmed that clinical samples from both patients were positive for HRTV. We subsequently performed entomologic investigations to determine tick density and HRTV prevalence among tick populations at the likely sites of exposure.