Hantavirus cardiopulmonary syndrome (HCPS) is a rare but frequently lethal acute zoonotic viral infection in rural North America. The rapidity of progression from febrile prodrome to cardiogenic shock and noncardiogenic pulmonary edema requiring intensive care creates high diagnostic urgency and a need for a rapid screening tool. In this retrospective cohort study, 2 pathologists scored blinded peripheral blood smears from 52 patients with HCPS and 128 seronegative patients referred for diagnosis of suspected hantavirus infection.

During the prodromal phase, thrombocytopenia was the only consistent abnormality and could be used to indicate hantavirus serologic testing. After the onset of pulmonary edema detected radiographically, the presence of 4 of 5 findings (thrombocytopenia, myelocytosis, hemoconcentration, lack of significant toxic granulation in neutrophils, and more than 10% of lymphocytes with immunoblastic morphologic features) has a sensitivity for HCPS of 96% and a specificity of 99% and missed no patients with HCPS who required intensive care. While each abnormality is commonly seen, the combination of at least 4 of these CBC count data and peripheral blood smear findings can guide early treatment and patient transport decisions until rapid, specific, serologic testing becomes widely available.

Author notes

Supported by grants P01 AI39780, “Emerging Viruses Research Center”; R01 AI36336 and R01 AI41692 from the US Public Health Service, Washington, DC; and by the Hantavirus Technical Services Agreement 95/665/14/010 from the Centers for Disease Control and Prevention, Atlanta, GA, and the New Mexico State Department of Health, Albuquerque.
Dr Chong is currently with the Department of Pathology, Case Western Reserve University, Cleveland, OH.