Hantavirus and the Andes Virus Outbreak

What Maryland Physicians Need to Know

An active multi-country outbreak of Andes virus, the only hantavirus strain capable of person-to-person transmission, has prompted the Maryland Department of Health (MDH) to begin monitoring two state residents following potential exposure. While confirmed cases remain far from Maryland and the risk to patients is considered very low, the outbreak warrants clinical awareness. Here is what you need to know to recognize, evaluate, and appropriately manage potential cases.

The Maryland Situation

On May 11, 2026, MDH confirmed it is monitoring two Maryland residents who were on a flight that briefly included a passenger from the M/V Hondius, a cruise ship at the center of a documented Andes virus cluster. Neither resident was a cruise ship passenger. MDH is coordinating with federal partners including the CDC and with Regional Emerging Special Pathogen Treatment Centers.

Key facts:

• No confirmed hantavirus cases in Maryland since 2019.
• Andes virus has never been detected in Maryland.
• Asymptomatic individuals are not considered infectious and passive monitoring is appropriate.
• MDH characterizes the current public risk in Maryland as very low.

Physicians who see patients presenting with fever, fatigue, myalgia, or respiratory distress following recent international travel, particularly travel to South America or potential contact with cruise ship passengers, should consider Andes virus in the differential and contact MDH. The incubation period for Andes virus ranges from 4 to 42 days.

MDH Contact for Reporting / Clinical Consultation

Maryland Department of Health — Infectious Disease Epidemiology & Outbreak Response: 410-767-6700

After hours (24/7): 410-795-1616

MDH Newsroom: health.maryland.gov

Background: Hantavirus and the Andes Strain

Hantaviruses are a group of viruses spread primarily through contact with infected rodent urine, feces, or saliva. In the Americas, hantavirus infection most commonly causes hantavirus pulmonary syndrome (HPS), a severe, potentially fatal respiratory illness. From 1993 through 2023, a total of 890 laboratory-confirmed HPS cases were reported in the United States making imported, person-to-person transmission a rare but recognized exception.

Andes virus is the only hantavirus known to spread from person to person. That transmission is rare and requires close, prolonged contact with a symptomatic individual including direct physical contact, time in enclosed spaces, or exposure to respiratory secretions or other bodily fluids. It does not spread through casual contact.

The outbreak is tied to the M/V Hondius, a cruise ship that departed Ushuaia, Argentina on April 1, 2026, and traveled across the South Atlantic. As of the CDC Health Alert Network advisory issued May 8, 2026 (HAN-00528), WHO had reported 8 cases (6 confirmed, 2 suspected) and 3 deaths.

Clinical Presentation

Per the CDC HAN-00528 advisory, HPS caused by Andes virus follows two phases:

Early phase (symptoms appear within 4–42 days post-exposure):

• Fever, fatigue, muscle aches particularly in large muscle groups (thighs, hips, back, shoulders)
• Headache, chills, dizziness
• GI symptoms (nausea, vomiting, diarrhea) in approximately half of patients
• Easily confused with influenza or other viral illness at onset

Late phase (4–10 days after initial symptoms):

• Cough, shortness of breath, chest tightness
• Rapid progression to respiratory failure and cardiogenic shock possible

Case fatality rate is approximately 38% among patients with severe respiratory symptoms. Early diagnosis is difficult — PCR and serology may not be accurate within the first 72 hours of symptom onset; repeat testing at 72+ hours is often necessary.

According to CDC clinical guidance, physicians should not wait for a confirmed diagnosis before initiating intensive supportive care if HPS is clinically suspected.

Testing, Reporting, and When to Suspect Hantavirus

Per the CDC Clinical Overview, test a patient for hantavirus if they present with HPS-compatible symptoms and have had:

• Rodent exposure (urine, droppings, saliva, nesting materials)
• Recent international travel particularly to South America or contact with the M/V Hondius outbreak cluster
• Close, prolonged contact with a known or suspected Andes virus case

Hantavirus is a nationally notifiable condition. Report suspected cases to MDH immediately (contact above). Specimens can be submitted to the state laboratory and the CDC can assist with confirmation and specimen submission.

Treatment and Clinical Management

There is no specific antiviral treatment for hantavirus. Early, aggressive supportive care is the most critical intervention including ICU admission for any patient with suspected HPS, ideally before diagnosis is confirmed.

Key management points (CDC HAN-00528):

• Initiate broad-spectrum antibiotic therapy while awaiting diagnosis as early symptoms overlap with bacterial illness
• Manage fever and pain with appropriate analgesics
• Anticipate rapid deterioration and have ventilator support ready
• ECMO can significantly improve survival (up to ~80%) in severe cases if initiated early
• Survivors typically recover quickly once the critical phase passes

For Andes virus specifically, CDC recommends the following inpatient precautions given its person-to-person transmission potential:

• Place patient in an airborne infection isolation room
• PPE: gown, gloves, eye protection, N95 or higher-level respirator upon room entry

CDC Guidance: Infection Control for Andes Virus in Healthcare Settings

Per CDC HAN-00528: patients with suspected or confirmed Andes virus should be placed in an airborne infection isolation room. Healthcare workers entering the room should use gown, gloves, eye protection, and an N95 or higher-level respirator.

Full precautions table: CDC Appendix A — Precautions for Selected Infections

Clinical Resources

• CDC HAN-00528: 2026 Multi-country Hantavirus Cluster Linked to Cruise Ship — Full health advisory with clinical guidance, testing, and biosafety recommendations (issued May 8, 2026)
• CDC Clinician Brief: Hantavirus Pulmonary Syndrome — Clinical overview, case definition, specimen submission guidance
• CDC Clinical Overview of Hantavirus — Broad clinical reference including HFRS and HPS
• CDC Hantavirus: Current Situation — Ongoing outbreak updates
• CDC Hantavirus Disease Trainings for Healthcare Providers — Free CME-eligible on-demand training modules on HPS diagnosis and treatment
• CDC Andes Virus Outbreak FAQ — Clinician and patient-facing FAQs on the cruise ship outbreak
• MDH Press Release: May 11, 2026 — Official MDH statement on Maryland monitoring situation
• Maryland Department of Health — health.maryland.gov — Monitor for ongoing MDH updates