Case Presentation: A healthy 35-year-old female from eastern Arizona presented in February with two weeks of fever, headache, epigastric pain, decreased appetite, two episodes of non-bloody emesis, dyspnea, and with orthopnea. She was cleaning out a trailer with rodent droppings inside a few days prior to the onset of her symptoms. Her vitals were notable for a HR of 137 and hypoxia requiring 2L of oxygen via nasal cannula. On exam, she was obese, alert, and using accessory muscles to breathe. Her lung exam showed basilar crackles, and her heart exam was notable for tachycardia.
Diagnostic studies were notable for CBC and peripheral smear showing hemoglobin of 12.3, platelets of 33, no schistocytes, no toxic granulation, and 13% blasts. Chest X-ray showed diffuse reticular pulmonary opacities. Given her history of rodent dropping exposure, the time of year, and her clinical presentation, empiric supportive treatment for Hantavirus was begun.
The patient received fluid restriction, as well as azithromycin and ceftriaxone for possible bacterial pneumonia. She was placed on Optiflow 70% FIO2/40L. FIO2 was decreased as she clinically improved over the course of five days with supportive care. Sepsis physiology, leukocytosis, thrombocytopenia, and hemoconcentration gradually improved, and hypoxia resolved. The diagnosis was confirmed by positive IgM and IgG for Hantavirus. She was discharged to home without additional medications, and the Department of Health was notified.

Discussion: Hantavirus is a rare but potentially catastrophic infection affecting patients exposed to rodent droppings while living in or visiting in endemic areas. Most –but not all- cases have occurred in the southwestern United States (New Mexico, Arizona, and Colorado) and California. The most common manifestation of infection is Hantavirus Cardiopulmonary Syndrome. Infection can rapidly progress to cardiogenic shock and noncardiogenic pulmonary edema making urgent screening and diagnosis necessary. When clinical suspicion is high based on presentation in the patient who has had a possible exposure to rodent droppings while in the appropriate geographic area, hospitalists should screen for Hantavirus by looking for thrombocytopenia, myelocytosis, hemoconcentration, lack of significant toxic granulation in neutrophils, and more than 10% of lymphocytes with immunoblastic morphologic features. The presence of more than 3 out of 5 findings make the possibility of Hantavirus infection high, and the presence of five factors is diagnostic. The diagnosis then can be confirmed by serologic test to look for antiviral antibodies.

Conclusions: Hospitalists should be vigilant for Hantavirus when seeing patients who have visited endemic areas, are exposed to rodent droppings, and who present with fever and thrombocytopenia. Early diagnosis and consideration of transfer to hospitals with experience treating this highly morbid infection (including availability of ECMO) is critical.