What Are the First Symptoms of Hantavirus in Adults?

If you’ve recently been around mouse droppings (or cleaned them up) and now you’re wondering about hantavirus, you’re in the right place.

In this article, we’ll cover the first symptoms of hantavirus in adults, what the timeline can look like after exposure, and the key signs that mean you should seek medical care quickly. We’ll also answer the questions people ask most: how you get hantavirus, how likely it is, whether it’s contagious, and how to prevent it in the first place.

First Symptoms of Hantavirus in Adults (Early Stage)

The tricky thing about the early stages of hantavirus is that the symptoms aren’t particularly unique, and they can begin showing themselves anywhere between 1-8 weeks after exposure. For most people, it can feel like a generic flu-like illness — the kind where you feel wiped out, achy, and off … but not necessarily sick enough to raise immediate red flags.

That’s why, if you know you’ve been around mice (or cleaned up droppings), it’s important to be a little more aware of how you’re feeling over the next month or more.

The 3 Most Common Early Symptoms

Most people who develop Hantavirus Pulmonary Syndrome (HPS) start with:

• Fatigue (the “hit by a truck” feeling)
• Fever
• Muscle aches (often in large muscle groups like thighs, hips, back, or shoulders)

Other Early Symptoms That Can Show Up

Not everyone gets all of these, but early symptoms can also include:

• Headache
• Chills
• Dizziness
• Nausea or vomiting
• Diarrhea
• Abdominal (stomach) pain

Can You Have Hantavirus Without a Fever?

Yes — it’s possible.

Fever is very common, but the absence of a fever isn’t enough to rule it out. If you’re experiencing other symptoms and you’ve had a meaningful rodent exposure, continue paying attention.

How to Know When Symptoms Are Serious?

The early phase typically lasts a few days, and this is where many people assume it’s just a bad cold or flu. In a lot of cases, it is just that — and people recover normally.

But if symptoms continue to escalate after day four, it's possible that you may be developing Hantavirus Pulmonary Syndrome (HPS) a much more serious (and deadly) condition.

You may experience:

• Cough
• Shortness of breath
• Chest tightness
• A feeling like they “can’t catch a full breath”

Breathing symptoms after a rodent exposure should be treated as urgent. This is when you should begin seeking immediate medical attention.

What Is Hantavirus Pulmonary Syndrome (HPS)?

When most people say “hantavirus,” what they’re usually talking about is Hantavirus Pulmonary Syndrome (HPS) — a serious illness that can develop after someone is exposed to certain hantaviruses carried by rodents.

Here’s the simplest way to think about it:

• Early on, HPS can look like the flu (fatigue, fever, muscle aches).
• The danger is when it shifts to the lungs. In the later phase, the body can start reacting in a way that makes it harder to breathe — and that’s when symptoms can escalate towards being life threatening.

How Dangerous is HPS?

HPS is rare, but it can become life-threatening quickly once it reaches the cardiopulmonary stage. Fluid can build up in the lungs and the body can struggle to get enough oxygen — which can lead to respiratory failure and the need for intensive hospital care.

According to the CDC, 35% of reported cases in which someone reached this stage of the virus resulted in death.

How Do You Contract Hantavirus?

Hantavirus is most often the result of exposure to a rodent-infested space, not necessarily to the rodent itself. This can happen when contaminated areas get disturbed, causing tiny particles from rodent urine, droppings, saliva, or nesting material to get stirred up and breathed in. 

(Are you in a HPS hotspot? Check our guide on Hantavirus Cases by State)

Most Common Ways Exposure Happens:

• Breathing in contaminated dust while cleaning or disturbing droppings/nests (especially in enclosed spaces)  
• Sweeping, vacuuming, or dry-sweeping droppings (this can kick particles into the air) 
• Opening and cleaning a long-closed shed, garage, cabin, barn, crawlspace, or storage area with signs of rodents  

Less Common, but Possible:

• Touching contaminated surfaces and then touching your mouth, nose, or eyes  
• Rodent bites (rare)  

In the U.S., hantaviruses aren’t known to spread from person to person. The notable exception is Andes virus (ANDV) in parts of South America, which can spread between people in close-contact situations.  

How to Prevent Hantavirus Infection

Preventing hantavirus really comes down to two simple ideas: keep rodents out, and don’t breathe in contaminated dust if you find droppings or nesting material.

1) Keep Rodents Out (reduce the chances of exposure)

• Seal entry points (gaps around doors, vents, pipes, and garages are common culprits).
• Remove attractants (food, trash, clutter, nesting materials).
• Address activity early (if you’re seeing droppings, set traps and keep checking them).
• Install a physical deterrent like the Box-Kat mouse barrier (particularly useful for garages and storage units)

2) Clean Up Droppings Safely (avoid stirring particles into the air)

• Don’t sweep or vacuum droppings. That’s the big mistake.
• Ventilate first, then wet everything down with disinfectant/bleach solution, let it soak, and wipe it up with paper towels while wearing gloves.
• Bag the waste, wash up, and launder anything that may have been contaminated.

Prevention isn’t about doing a hundred things perfectly. It’s about avoiding one risky step — dry cleanup. When in doubt: wet it, disinfect it, wipe it up.