The basics

Hantaviruses are a family of viruses (genus Orthohantavirus) carried mainly by wild rodents. Different rodent species carry different hantavirus strains, and people usually get sick after breathing in tiny particles from rodent urine, droppings or saliva. Hantaviruses cause two main illness patterns in humans.

The two main diseases

1. Hantavirus Pulmonary Syndrome (HPS)

Found mostly in the Americas. Caused by New World hantaviruses such as Sin Nombre virus (United States) and Andes virus (South America). HPS attacks the lungs and can progress rapidly from flu-like symptoms to severe respiratory failure.

2. Hemorrhagic Fever with Renal Syndrome (HFRS)

Found mostly in Europe and Asia. Caused by Old World hantaviruses such as Hantaan, Seoul, Puumala and Dobrava. HFRS primarily affects the kidneys and blood vessels and ranges from mild to severe.

Known strains worth knowing

Sin Nombre virus — main HPS strain in the United States; carried by deer mice.
Andes virus — circulates in Argentina and Chile; the only hantavirus with documented person-to-person transmission. Read more about how it spreads.
Seoul virus — carried by brown rats worldwide; usually causes milder HFRS.
Puumala virus — common in northern Europe; causes a milder form of HFRS sometimes called nephropathia epidemica.

A brief history

Hantaviruses were first identified in the late 1970s near the Hantan River in Korea after outbreaks among soldiers during the Korean War. HPS emerged in the public eye in 1993, after an outbreak in the Four Corners region of the U.S. led to the discovery of Sin Nombre virus. Andes virus was identified shortly after in South America, where person-to-person spread was documented for the first time.

How worried should I be?

Human cases are rare overall, but the illness can be serious. The risk depends heavily on your environment (rodent exposure), location, and which strain is circulating. See symptoms, transmission, and prevention for what matters most day-to-day.

Sources

U.S. Centers for Disease Control and Prevention — Hantavirus.
World Health Organization — Hantavirus disease.
Pan American Health Organization — Andes virus surveillance.