HANTAVIRUS
HOW IT SPREADS & WHAT IT DOES

What hantavirus actually is

Hantaviruses are a group of viruses (genus Orthohantavirus) that live in rodents and a handful of other small mammals. The animals themselves don't get sick — they carry the virus quietly for life, shedding it in their urine, saliva, and droppings. People are the unlucky bystanders. When humans pick it up, it can cause anything from a flu-like illness to a serious, sometimes fatal disease of the lungs or kidneys.

How people get infected

Almost every human case starts with rodent waste. The most common route is breathing in tiny airborne particles after that waste gets disturbed — sweeping out a shed, opening up a cabin in the spring, moving boxes in a garage, or pulling apart insulation in a barn. The virus rides along on the dust.

Less often, people are infected by touching contaminated surfaces and then their mouth, eyes, or nose, or by eating food or drinking water that rodents have gotten into. Rodent bites can transmit the virus too, but they're an uncommon cause.

The illnesses it causes

Different hantaviruses cause different diseases, and which one you get depends largely on where you are in the world.

Hantavirus Pulmonary Syndrome (HPS)

This is the form found in the Americas, and it's what Canadians need to know about. After an incubation period of one to several weeks, it starts looking like the flu — fever, muscle aches, fatigue. Then, often abruptly, the lungs begin to fill with fluid and breathing becomes difficult. HPS is dangerous: roughly a third to half of hospitalized patients don't survive, and there is no specific antiviral treatment, only supportive care. In Canada and the United States, the culprit is almost always Sin Nombre virus.

Hemorrhagic Fever with Renal Syndrome (HFRS)

HFRS is the Eurasian counterpart, common across parts of Europe, Russia, China, and Korea. It targets blood vessels and the kidneys rather than the lungs, with symptoms ranging from mild fever to severe bleeding, shock, and kidney failure. Severity depends heavily on which strain is involved — Hantaan and Dobrava viruses are the more dangerous ones, while Puumala (the most common cause in northern Europe) is generally milder.

One strain, Seoul virus, is carried by Norway rats and brown rats, which means it shows up wherever those rats live — essentially everywhere. It usually causes a milder version of HFRS but is worth knowing about given how widespread its host is.

The rodents that carry it

Each hantavirus has co-evolved with a particular rodent species, and the geography of the disease tracks the geography of the host.

In Canada, the main concern is the deer mouse (Peromyscus maniculatus), which carries Sin Nombre virus and is found across most of the country, particularly in rural, wooded, and prairie areas. The white-footed mouse and the red-backed vole can also carry hantaviruses and overlap with the deer mouse's range in parts of southern and eastern Canada. Further south, cotton rats and rice rats carry their own strains in the United States.

Outside the Americas, the cast of carriers changes: bank voles in Scandinavia and central Europe (Puumala virus), striped field mice in East Asia (Hantaan virus), yellow-necked mice in the Balkans (Dobrava virus), and various long-tailed rice rats and their relatives in South America (Andes virus and others).