CDC Emerging Infectious Diseases Seroprevalence of Heartland Virus Antibodies in Blood Donors, Northwestern Missouri, USA Feb 2019 Estimated the seroprevalence of Heartland virus antibodies is 0.9% in a sample of blood donors from northwestern Missouri, … where human cases and infected ticks have been identified. Although these findings suggest that some past human infections were undetected, the estimated prevalence is low.