HANTAVIRUS
SYMPTOMS & WHEN TO ACT

Hantaviruses cause two main illnesses in humans, and which one you're at risk for depends on geography. In Canada and the rest of the Americas, the concern is Hantavirus Pulmonary Syndrome (HPS), which attacks the lungs. In Europe and Asia, the same family of viruses tends to cause Hemorrhagic Fever with Renal Syndrome (HFRS), which goes after the kidneys and blood vessels. Symptoms typically begin one to eight weeks after exposure to rodent droppings, urine, or saliva.

Hantavirus Pulmonary Syndrome (HPS)

HPS usually shows up two to four weeks after exposure, though the incubation can stretch from one week to two months. It moves through two phases, and the gap between them is short.

The first phase: feels like the flu

For three to five days, HPS is almost indistinguishable from a bad case of influenza. The hallmarks are fever, chills, and severe muscle aches that concentrate in the large muscle groups — the thighs, hips, lower back, and shoulders. Most people also feel exhausted and develop a headache. Around half experience nausea, vomiting, diarrhea, or abdominal pain. There's no cough yet, which is what makes the diagnosis so easy to miss in this window.

The second phase: the lungs fill

Four to ten days in, the disease turns. Patients develop a dry cough and increasing shortness of breath as fluid begins to accumulate in the lungs. From there, deterioration can be rapid — often within 24 hours — with the heart rate climbing, blood pressure dropping, and breathing becoming severely impaired. Most people who reach this stage need to be hospitalized, and many require an ICU. There is no specific antiviral; treatment is supportive, focused on oxygenation and circulation, which is why getting in early matters so much.

Hemorrhagic Fever with Renal Syndrome (HFRS)

HFRS has a shorter incubation, usually one to two weeks, and tends to follow a more drawn-out course than HPS. Severity ranges widely depending on which strain is responsible — Hantaan and Dobrava viruses can be life-threatening, while Puumala (common in northern Europe) is often relatively mild.

The illness opens with sudden high fever, an intense headache, and aching in the back and abdomen, often with nausea and vomiting. A distinctive feature in this phase is visual disturbance — blurred vision is reported in a significant fraction of cases. As things progress, the face flushes, the eyes redden, and small red or purple spots (petechiae) may appear on the skin from blood vessel damage. Blood pressure can drop sharply, kidney function falters, and in severe cases there is internal bleeding.

Clinically, HFRS is often described as moving through five phases: an initial febrile stage, a hypotensive stage where blood pressure crashes, an oliguric stage where the kidneys produce little urine, a polyuric recovery stage where urine output rebounds, and a long convalescent stage. Not every patient passes through all five clearly, but the pattern helps doctors anticipate what comes next.

When to get help

The single most useful thing you can do at the hospital is tell the clinician about the rodent exposure. Hantavirus is rare enough that it's not on most doctors' first list of suspects when someone walks in with flu symptoms, and the diagnosis hinges on knowing to test for it. There is no specific cure, but early supportive care — fluids, oxygen, ICU monitoring when needed — substantially improves the chances of survival.