Last updated: May 17, 2026, Peer-reviewed by Dr. Sabrina Berdouk.
Hantavirus is one of those diagnoses most emergency physicians may never personally see—but when it matters, it matters fast.
The early presentation can look like influenza, COVID-19, gastroenteritis, sepsis, pneumonia, myocarditis, or pulmonary edema. Then, in a subset of patients, the disease can abruptly transition into severe hypoxemia, shock, myocardial depression, dysrhythmia, renal failure, or hemorrhage. The ED challenge is not to diagnose every viral syndrome as hantavirus. The challenge is to recognize the rare patient whose viral prodrome plus exposure history plus early cardiopulmonary deterioration should trigger isolation, public health notification, and aggressive supportive care.
This post is based on the uploaded EM clinical summary and current CDC/WHO guidance.
The two major clinical patterns
Hantaviruses are rodent-borne viruses that cause two major clinical syndromes.
The first is hemorrhagic fever with renal syndrome, classically associated with “Old World” hantaviruses in Europe, Asia, and parts of Africa. These patients may develop fever, thrombocytopenia, bleeding, acute kidney injury, oliguria, fluid overload, and shock.
The second is hantavirus pulmonary syndrome, also called hantavirus cardiopulmonary syndrome, classically associated with “New World” hantaviruses in the Americas. This is the syndrome most relevant to the recent Andes virus concern. CDC notes that HPS can begin with nonspecific flu-like symptoms and may progress to severe respiratory disease; it is fatal in nearly 4 in 10 infected patients.
Andes virus: the important exception
Most hantaviruses are acquired from rodents through contact with urine, feces, saliva, nesting material, contaminated dust, or, less commonly, rodent bites or scratches. People are usually infected by inhaling aerosolized virus during activities like cleaning rodent-infested spaces, staying in cabins, camping, hiking, or working in rodent-exposed environments.
Andes virus is different. It is a South American hantavirus that can cause HPS and is the only hantavirus currently known to spread person-to-person. CDC describes this spread as rare and usually limited to close contact with a sick person, including direct physical contact, prolonged time in close or enclosed spaces, or exposure to body fluids.
That point matters for ED risk communication. Andes virus is dangerous for the individual patient, but it does not behave like COVID-19. CDC’s current guidance states that person-to-person transmission appears relatively rare, generally associated with prolonged close contact, and that there is no documented evidence of presymptomatic transmission.
For the current cruise-associated Andes virus outbreak, CDC states that the risk of a pandemic from this outbreak and the overall risk to the American public and travelers remains extremely low.
The physiology: capillary leak plus cardiac dysfunction
The key pathophysiology is endothelial dysfunction.
Hantaviruses target small vessels and capillaries. In HPS, the pulmonary capillary bed becomes leaky. Plasma moves out of the intravascular space and into the lungs, creating rapidly progressive noncardiogenic pulmonary edema. At the same time, patients may develop myocardial depression and shock.
A useful mental model:
The tank is leaking, the lungs are flooding, and the pump may be failing.
That is why large-volume fluid resuscitation can be dangerous. These patients may be hypotensive, but their vascular permeability is abnormal. Too much crystalloid can worsen pulmonary edema. The ED approach is careful fluid, early vasopressors when needed, close cardiopulmonary monitoring, and early escalation to ICU or ECMO-capable care. CDC emphasizes careful fluid administration, oxygen, ventilation when needed, and monitoring/adjustment of cardiac function.
The timeline: the clue is often in the story
The incubation period is long enough that the exposure may not be obvious unless we ask.
For Andes virus, CDC lists an incubation period of 4 to 42 days, with a median of 18 days. Compatible symptoms include fever, myalgias, chills, GI symptoms, cough, shortness of breath, chest pain, and difficulty breathing after exposure.
The classic clinical pattern has two phases:
Early phase: fever, chills, fatigue, headache, myalgias, back pain, nausea, vomiting, diarrhea, abdominal pain, and decreased appetite.
Cardiopulmonary phase: cough, chest pain, dyspnea, hypoxia, pulmonary edema, hypotension, myocardial depression, and dysrhythmia.
The danger is the transition. A patient may initially look like they have a routine viral illness, then rapidly develop hypoxemic respiratory failure and shock.
When should an ER doctor think of hantavirus?
Do not screen every patient with fever for hantavirus. Instead, look for the pattern:
Viral prodrome + exposure risk + respiratory symptoms, shock, thrombocytopenia, hemoconcentration, renal injury, or unexplained pulmonary edema.
Ask specifically about:
Recent camping, hiking, cabins, barns, sheds, farms, or rodent-infested buildings
Cleaning or sweeping enclosed spaces with rodent droppings
Occupational exposure to rodents or contaminated environments
Travel to endemic areas, especially rural South America for Andes virus
Close contact with a symptomatic suspected or confirmed Andes virus patient
Cruise, aircraft, household, or enclosed-space exposure during a known outbreak
The uploaded clinical summary also highlights a practical ED point: in undifferentiated sick patients, keep evaluating for common diagnoses—sepsis, influenza, COVID-19, pneumonia, pulmonary embolism, myocarditis, cardiogenic pulmonary edema, leptospirosis, Legionella, Q fever, and other viral syndromes—while assessing hantavirus exposure risk.
Isolation: act before the test comes back
If hantavirus—especially Andes virus—is clinically plausible, isolation should not wait for confirmation.
For known or suspected Andes virus infection in healthcare settings, CDC recommends placement in an airborne infection isolation room when available, with gown, gloves, eye protection, and an N95 or higher-level respirator when entering the room.
A practical ED workflow:
Recognize: compatible symptoms plus exposure risk.
Isolate: airborne room if available; PPE with respiratory and eye protection.
Notify: call the local/state health department early.
Support: oxygen, cautious fluids, pressors, ventilation, and early ICU/ECMO planning.
This is not because the ED should panic. It is because early containment protects staff and patients, and early consultation helps with testing, monitoring, and disposition.
Diagnosis: public health needs to be involved
Hantavirus testing is not usually an ED “send it and forget it” test.
CDC advises clinicians with compatible symptoms and exposure risk to contact their state, tribal, local, or territorial health department. CDC’s Viral Special Pathogens Branch can provide consultation through the CDC Emergency Operations Center, and CDC notes that specimens are not accepted without prior consultation.
Diagnostic confirmation may include:
IgM positivity
Rising IgG titers
PCR positivity
Immunohistochemistry in fatal cases
One important pearl: early testing can be falsely negative. CDC’s Andes virus guidance states that if serum collected within 72 hours of symptom onset is negative for New World hantavirus IgM and IgG, a second specimen collected more than 72 hours after symptom onset should be submitted to rule out infection.
Treatment: supportive care is the treatment
There is no licensed specific antiviral treatment or vaccine for hantavirus infection. WHO states that care is supportive and focuses on close clinical monitoring and management of respiratory, cardiac, and kidney complications.
For the ED, this means:
Give oxygen early.
Use noninvasive ventilation or intubation when appropriate.
Treat shock with cautious fluid and early vasopressors.
Avoid reflexive large-volume crystalloid if pulmonary edema is developing.
Use broad-spectrum antibiotics if the patient is undifferentiated and bacterial sepsis remains possible.
Avoid NSAIDs when thrombocytopenia, renal injury, or hemorrhage is a concern.
Transfer early to an ICU or ECMO-capable center if the patient is deteriorating.
CDC notes that early ECMO at the first sign of decompensation has been associated with an 80% survival rate despite cardiopulmonary collapse.
Ribavirin has been studied in HPS but has not been shown to be effective for HPS treatment.
Disposition: don’t be reassured too easily
A symptomatic patient with suspected or confirmed hantavirus generally needs admission, often ICU-level care, because deterioration can be abrupt.
Patients with suspected HPS should be treated as potentially unstable even before confirmation. CDC notes that most HPS patients develop some degree of hypotension within 24 hours of initial evaluation, with progressive pulmonary edema and hypoxia often requiring mechanical ventilation. Fatal cases may involve severe myocardial depression progressing to bradycardia, electromechanical dissociation, ventricular tachycardia, or ventricular fibrillation.
For asymptomatic exposed patients, disposition should be guided by public health. CDC’s current Andes virus guidance recommends monitoring for 42 days after last potential exposure, with symptom monitoring and instructions to self-isolate immediately if symptoms develop.
POCUS-guided resuscitation: leaking, failing, bleeding, or mimicking?
POCUS can play an important role when a suspected hantavirus patient begins to deteriorate.
It does not diagnose hantavirus.
It helps the emergency physician identify the dominant shock physiology before the patient abruptly crashes.
The key question is:
Is the patient leaking, failing, bleeding, or mimicking another emergency?
Lung ultrasound may detect early interstitial edema, diffuse B-lines, or pleural effusions before the chest radiograph fully declares itself.
This matters because repeated crystalloid boluses may worsen oxygenation if the pulmonary capillaries are already leaking.
Cardiac views can identify myocardial depression, low stroke volume, RV strain, tamponade, or another obstructive or cardiogenic mimic.
IVC assessment may suggest low effective circulating volume, but this is the major pitfall.
In hantavirus cardiopulmonary syndrome, the patient can be vascularly dry but lung-wet.
A small, collapsible IVC should not automatically trigger large-volume fluid resuscitation.
Instead, use small fluid challenges only when appropriate.
Then reassess repeatedly:
the lungs,
the heart,
the blood pressure,
and the oxygenation.
If pulmonary edema, shock, or myocardial dysfunction is emerging, move early to vasopressors, ventilatory support, ICU care, and ECMO-capable transfer.
In this setting, POCUS is the bedside physiology monitor.
It helps us avoid flooding a leaking capillary bed while detecting the weak pump or dangerous mimic early.
The ED bottom line
Hantavirus is rare, but it is an emergency medicine diagnosis because the patient can crash quickly.
The pattern to remember is:
Exposure risk + viral prodrome + pulmonary edema/hypoxia/shock = think hantavirus.
The action plan is:
Isolate early. Call public health early. Support the physiology early. Transfer early if cardiopulmonary failure is developing.
For the worried well, assess exposure risk and coordinate with the health department. For the crashing patient, do not wait for the test. Treat the lungs, support the circulation, protect the team, and get help early.
