Hemorrhagic fever with renal syndrome (HFRS) is a rare, life-threatening syndrome caused by an Orthohantavirus (family Hantaviridae, order Bunyavirales). Specific hantaviruses that have been identified as causes of HFRS are the Hantaan virus, Seoul virus, Puumala virus, and Dobrava / Belgrade virus. HFRS is primarily described in Eurasia and occurs most commonly in Asia with the highest prevalence in Korea, China, and eastern Russia. In Korea, most infections occur during the rodent breeding season in late autumn and early winter. 

In the United States, Seoul virus is the only form known to cause HFRS, and transmission to humans is rare. In 2016-2017, an outbreak of Seoul virus infections in humans, from exposure to pet rats, was identified in the United States and Canada and traced back to rat-breeding facilities.

Hantaviruses reside in rodent reservoirs and are excreted in rodent urine, feces, and saliva. Natural infection is acquired by exposure to contaminated rodent body fluids and droppings, inhalation of aerosol or dust containing rodent excreta, and by rodent bites. Person-to-person transition may occur but is extremely rare.

Patients present with a febrile illness. Anorexia, emesis, diarrhea, headache, abdominal pain, and conjunctival injection are all common concurrent symptoms. Symptoms typically develop 1-2 weeks after exposure, although the incubation period may be as long as 8 weeks. HFRS can progress to septic shock and renal failure, and overall mortality is estimated at approximately 1%-15%, depending on the specific virus.

Laboratory findings are relatively nonspecific, characterized by a leukocytosis, thrombocytopenia, acute kidney injury (elevated blood urea nitrogen and creatinine), and transaminase (aspartate aminotransferase and alanine aminotransferase) elevation. Diagnosis can be confirmed by immunologic or molecular testing specific for the presence of hantavirus in the serum or biopsied tissue.

Hantavirus cardiopulmonary syndrome (HCPS) is also caused by hantaviruses, albeit different viruses than those that cause HFRS, and is endemic in the Americas.