Hantavirus Diagnosis: Key Clinical Indicators and Laboratory Testing

What Is Hantavirus?

Hantaviruses are a family of viruses spread mainly by rodents. They can cause serious illness or death in people. Most hantaviruses are not transmitted from person to person. People get hantavirus from contact with rodents like rats and mice, especially when exposed to their urine, droppings, and saliva. It can also spread through a bite or scratch by a rodent, but this is rare.

In the United States, the primary strain causing human illness is Sin Nombre virus (SNV), carried by the deer mouse (Peromyscus maniculatus). This strain causes Hantavirus Pulmonary Syndrome (HPS) — a severe, rapidly progressive respiratory illness with a historical case fatality rate of approximately 38% in laboratory-confirmed U.S. cases, per CDC surveillance data.

Surveillance of hantavirus began in 1993, and as of the end of 2023, only 890 cases of hantavirus disease had been reported in the United States. These were all laboratory-confirmed cases and included both pulmonary and non-pulmonary hantavirus infection.

How Hantavirus Spreads

Most hantaviruses are not transmitted from person to person. The primary exposure routes confirmed by the CDC include:

• Inhalation of aerosolized particles from infected rodent urine, droppings, or saliva — the most common route
• Direct mucosal contact with rodent excreta, followed by touching the eyes, nose, or mouth
• Rodent bite or scratch — documented but rare

Risk is highest when disturbing rodent-infested enclosed spaces — cleaning cabins, sheds, attics, or storage areas — without appropriate respiratory protection. Populations with elevated exposure risk include agricultural workers, pest control workers, campers, hikers, and anyone opening or cleaning rural structures after long periods of disuse.

Recognizing Hantavirus: Symptoms and Clinical Presentation

Symptoms of HPS usually start to show 1 to 8 weeks after contact with an infected rodent. The clinical course of hantavirus pulmonary syndrome progresses through two distinct phases:

Early (Prodromal) Phase — Days 1 to 5

Early symptoms are nonspecific and frequently resemble influenza, COVID-19, or a gastrointestinal illness. They include:

• Fever and chills
• Fatigue
• Myalgia — particularly pronounced in the thighs, hips, back, and shoulders
• Headache
• Nausea, vomiting, diarrhea, and abdominal pain

The nonspecific nature of this phase is the primary reason laboratory confirmation is essential. Clinical presentation alone cannot reliably distinguish early HPS from influenza, COVID-19, leptospirosis, dengue, or sepsis.

Cardiopulmonary Phase

As disease progresses — typically 4 to 10 days after symptom onset — patients develop cough and increasing shortness of breath as fluid accumulates in the lungs. This phase can deteriorate rapidly into acute respiratory distress syndrome (ARDS) and cardiogenic shock. Most fatalities occur during this stage. Patients who reach this phase typically require intensive care, and some require extracorporeal membrane oxygenation (ECMO) support.

There is no specific antiviral treatment approved for hantavirus in the United States. Care is supportive, reinforcing the clinical importance of early identification and appropriate hospital-level escalation.

Diagnosing Hantavirus: Key Clinical Indicators and Laboratory Testing

Hantavirus infection cannot be confirmed on clinical presentation alone. Laboratory testing is required. Providers should consider hantavirus when a patient presents with all three of the following:

1. A history of known or suspected exposure to wild rodents or their excreta within the prior 1–8 weeks
2. A febrile illness with prominent myalgia and no identified alternative cause
3. Progressive respiratory symptoms or unexplained thrombocytopenia, elevated hematocrit, or bilateral pulmonary infiltrates

Primary Laboratory Tests

Repeat diagnostic testing is often performed 72 hours after initial symptom onset when initial results are equivocal, as early IgM titers may be below detection threshold. A negative initial serology does not rule out hantavirus in a patient with strong clinical and exposure history.

Hantavirus testing is specialized and is typically processed through public health laboratories, reference laboratories, or select academic medical centers. When ordering, providers should contact their state or local health department, as hantavirus is a nationally notifiable condition in the United States. State health departments coordinate specimen submission to the CDC for confirmation when needed.

U.S. Case Distribution and Surveillance Data

Hantavirus is a reportable disease in the United States. Key surveillance facts confirmed by the CDC:

• As of the end of 2023, 890 total laboratory-confirmed cases have been reported in the U.S. since 1993.
• Cases have been confirmed in 36 U.S. states, concentrated primarily in the rural West and Southwest.
• Over the five-year period from 2020 to 2025, Arizona led all states with 26 confirmed cases, followed by New Mexico (25) and Colorado (13).
• The historical case fatality rate for HPS in the U.S. is approximately 38%, per CDC data.
• In 2025 across the Region of the Americas, eight countries reported 229 cases and 59 deaths (PAHO/WHO).

The 2026 Outbreak: What Providers Need to Know

In May 2026, a cluster of severe acute respiratory illness caused by Andes hantavirus was linked to passengers and crew of the Dutch expedition cruise ship MV Hondius. As of May 26, 2026, the WHO and CDC confirmed 13 cases (11 confirmed, 2 probable) across multiple countries, including 3 deaths.

Seventeen American passengers were repatriated on a U.S. government medical flight to a Nebraska quarantine facility. On May 18, 2026, the CDC issued a Health Alert Network (HAN) notice providing updated testing guidance for clinicians managing recently repatriated passengers. As of May 31, 2026, monitoring of U.S. repatriates remains ongoing.

This outbreak has generated significant public attention due to the involvement of Andes virus — the only hantavirus strain with documented person-to-person transmission under specific conditions of close, prolonged contact.

When to Order Hantavirus Testing

The CDC recommends considering hantavirus laboratory testing for patients who meet the following criteria:

• Symptoms compatible with HPS: febrile illness, significant myalgia, and new or worsening respiratory symptoms
• Known or suspected exposure to wild rodents or rodent-contaminated environments within the prior 1–8 weeks
• No alternative diagnosis that adequately explains the full clinical picture

Supportive laboratory findings that raise clinical suspicion include: thrombocytopenia (a hallmark early finding), leukocytosis with a left shift, hemoconcentration (elevated hematocrit), hypoalbuminemia, and bilateral pulmonary infiltrates on imaging. These findings — combined with a relevant exposure history — should prompt serologic testing and early specialist consultation.

For suspected cases, report to your state or local health department. The CDC maintains updated clinical guidance for providers at cdc.gov/hantavirus. Additional patient education materials are available via the CDC Hantavirus Brochure (PDF).

Prevention: What to Advise Patients

No FDA-approved hantavirus vaccine exists in the United States. Prevention depends on reducing rodent exposure. The CDC recommends the following for individuals at risk:

• Seal gaps and holes in building foundations, walls, and rooflines to prevent rodent entry
• Use gloves and N95 or higher respiratory protection when cleaning areas with known or suspected rodent activity
• Wet contaminated surfaces with a disinfectant before sweeping to prevent aerosolization of dried viral particles
• Use rodent traps and follow proper disposal protocols — do not handle dead rodents without protection
• Air out enclosed structures (cabins, sheds, storage areas) for at least 30 minutes before cleaning if rodent activity is suspected
• Avoid sleeping on bare ground in areas with rodent activity; use a ground cover or elevated cot

Providers serving patients with occupational or recreational exposure risk — including agricultural workers, pest control professionals, wildlife biologists, military personnel, and outdoor recreationists in endemic regions — should maintain hantavirus awareness as part of the differential diagnosis for compatible febrile illness.