Hantavirus (Hantavirus Pulmonary Syndrome)

**Hantaviruses** are RNA viruses belonging to the family Hantaviridae that primarily infect rodents and other small mammals. Humans are accidental hosts, typically infected through inhalation of aerosolized particles from rodent urine, droppings, or saliva. Different hantavirus species cause different clinical syndromes based on their geographic distribution and tissue tropism. **Two Main Clinical Syndromes:** **1. Hantavirus Pulmonary Syndrome (HPS) — The Americas:** - Primary syndrome in North and South America - Caused by Sin Nombre virus (USA), Andes virus (South America), and others - Predominantly affects the lungs causing severe respiratory failure - Case fatality rate 30-40% - Examples: Sin Nombre virus, Andes virus, Black Creek Canal virus **2. Hemorrhagic Fever with Renal Syndrome (HFRS) — Europe/Asia:** - Primary syndrome in Europe and Asia - Caused by Hantaan virus, Seoul virus, Puumala virus, Dobrava virus - Predominantly affects the kidneys causing renal failure - Case fatality rate varies 1-15% depending on strain - Examples: Hantaan virus, Puumala virus, Dobrava virus, Seoul virus **The Andes Virus — A Unique Concern:** The Andes hantavirus, found primarily in Argentina and Chile, is the ONLY hantavirus known to be capable of person-to-person transmission. This makes it uniquely concerning for several reasons: - **Limited human-to-human spread** documented through close prolonged contact - **Healthcare workers** at risk caring for infected patients without proper PPE - **Household contacts** can become infected - **Cruise ship spread** documented (May 2026 MV Hondius outbreak) - Spread still requires close contact — NOT easily transmitted in casual settings **Transmission Routes (Standard for Most Strains):** **Primary Route - Aerosol Inhalation:** - Inhalation of aerosolized virus particles - Released when rodent urine, droppings, or nesting materials are disturbed - Common in poorly maintained sheds, garages, storage areas - Highest risk during cleaning of rodent-infested spaces **Direct Contact:** - Direct contact with rodents (handling, bites) - Contact with rodent excretions through skin breaks - Contact with mucous membranes (eyes, nose, mouth) - Consumption of food/water contaminated by rodent droppings **NOT Transmitted Through:** - Casual human contact - Air conditioning systems - Insect bites - Touching contaminated surfaces (for most strains) - Sexual contact (not significant route) **The 2026 MV Hondius Outbreak Context:** The May 2026 outbreak that brought hantavirus back into global awareness: - Originated aboard MV Hondius cruise ship departing Argentina - Caused by Andes virus strain - 8 cases identified across 6 countries (as of May 11, 2026) - 3 deaths reported, 2 Andes-confirmed - WHO contact tracing initiated globally - US CDC and Singapore joined surveillance efforts - Overall global risk assessed as LOW - No community transmission documented - All cases linked to original cruise ship cluster This outbreak demonstrated the unique transmission potential of Andes virus while reinforcing that even this strain spreads only through close contact, not casual exposure.

## Root Causes **Hantavirus infection occurs through specific exposure routes, almost always involving infected rodents:** **Primary Source: Infected Rodents** *North America (Sin Nombre virus):* - **Deer mouse** (Peromyscus maniculatus) — primary reservoir - White-footed mouse, cotton rat, rice rat (other species) - Mice asymptomatic carriers shedding virus in urine, droppings, saliva *South America (Andes virus):* - **Long-tailed pygmy rice rat** (Oligoryzomys longicaudatus) - Multiple other rodent species - Higher density in rural and wilderness areas - Cyclic population expansions increase outbreak risk *Europe (Puumala virus, others):* - **Bank vole** (Myodes glareolus) — primary for Puumala - Yellow-necked mouse, striped field mouse (other species) - Forest habitats common reservoirs *Asia (Hantaan, Seoul viruses):* - **Striped field mouse** (Apodemus agrarius) — Hantaan - **Norway rat** (Rattus norvegicus) — Seoul - Urban populations can carry Seoul virus **Exposure Mechanisms:** **1. Aerosol Inhalation (Most Common):** - Disturbing rodent nests, droppings, urine - Cleaning poorly maintained spaces - Sweeping or vacuuming infested areas without precautions - Vehicle interior with rodent activity **2. Direct Contact:** - Handling infected rodents - Rare rodent bites - Skin contact with broken skin and rodent material **3. Food/Water Contamination:** - Food stored without rodent protection - Water contaminated by rodent droppings - Less common but documented **4. Person-to-Person (Andes Virus Only):** - Close prolonged contact with infected patient - Respiratory droplet exposure - Healthcare workers without proper PPE - Household contacts **Risk Factors:** *Geographic:* - **Living in or visiting endemic areas** (rural Americas, certain European/Asian regions) - **Wilderness activities** in known habitats - **Recently disturbed areas** with rodent populations *Occupational:* - **Agricultural workers** - **Forestry workers** - **Wildlife professionals** - **Pest control workers** - **Military personnel** in field training - **Construction workers** in rural areas - **Cleaning workers** of long-abandoned spaces *Recreational:* - **Hikers and campers** in endemic areas - **Hunters** - **Researchers** studying wildlife - **Renovation of vacation cabins** *Environmental:* - **Recent rodent population expansion** (often weather-driven) - **Poor pest control** in dwellings - **Long-vacant structures** with rodent invasion - **Poor food storage practices** **Why Outbreaks Occur:** Hantavirus outbreaks are typically associated with environmental conditions that favor rodent population expansion: - **Heavy rainfall** leading to abundant food sources - **Mild winters** with high rodent survival - **Drought conditions** that drive rodents toward human dwellings - **Agricultural cycles** with abundant grain - **Natural disturbances** (fires, floods) altering habitats The El Niño Southern Oscillation has been linked to rodent population dynamics and hantavirus emergence in the Americas.

## Treatment Approach **There is NO specific antiviral treatment approved for hantavirus infection. Management focuses on aggressive supportive care.** ## Critical Care Management (HPS Cardiopulmonary Phase) **Setting:** - **ICU admission essential** for cardiopulmonary phase - Most patients require mechanical ventilation - Many need vasopressor support - Some require ECMO (extracorporeal membrane oxygenation) **Respiratory Support:** - **Mechanical ventilation** with low tidal volume strategies (similar to ARDS) - **PEEP optimization** for oxygenation - **Prone positioning** in severe ARDS - **ECMO** for refractory respiratory failure (in centers with capability) **Hemodynamic Support:** - **Careful fluid management** — capillary leak makes balance critical - **Vasopressor support** — norepinephrine, vasopressin, epinephrine - **Cardiac monitoring** for shock states - **Avoid over-resuscitation** — exacerbates pulmonary edema **Coagulation Management:** - Monitor for disseminated intravascular coagulation (DIC) - Platelet transfusions if severe thrombocytopenia with bleeding - Fresh frozen plasma for coagulopathy - Address bleeding complications **Renal Support:** - Monitor for acute kidney injury - Dialysis if needed - Particularly important in HFRS (renal syndrome) ## Specific Pharmacological Approaches **Investigational/Limited Evidence:** *Ribavirin:* - **HFRS**: Some evidence for benefit, especially early administration - **HPS**: NOT effective for hantavirus pulmonary syndrome - Used in some centers experimentally *Immune Therapy:* - **Convalescent plasma** — experimental - **Hyperimmune globulin** — limited availability - Used in research settings *Methylprednisolone:* - Studied in clinical trials - No definitive benefit shown - Not standard treatment ## Critical Care Pearls **1. Recognize Capillary Leak Early:** - HPS patients have rapid plasma leak into tissues - Aggressive crystalloid resuscitation worsens pulmonary edema - Careful balance between perfusion and pulmonary congestion **2. Avoid Excessive Fluid Administration:** - Use vasopressors over fluid boluses when possible - Monitor central venous pressure - Daily fluid balance critical **3. Early ECMO Consideration:** - Patients who survive often need ECMO - Don't delay transfer to ECMO center - Refractory hypoxemia or hemodynamic instability indications **4. Infection Control (For Andes Virus):** - **Standard contact and droplet precautions** for confirmed Andes cases - **PPE for healthcare workers** during procedures - **Isolation of confirmed cases** - **Avoid close contact** in early symptomatic phase ## Prognosis **Factors Associated with Better Outcomes:** - Early recognition and ICU transfer - Younger age - No comorbidities - Access to ECMO if needed - Centers with hantavirus experience **Factors Associated with Worse Outcomes:** - Delayed recognition - Severe cardiopulmonary collapse at presentation - Multi-organ failure - Older age - Comorbid conditions **Mortality Rates:** - **Sin Nombre virus (North American HPS)**: 30-40% - **Andes virus**: 30-50% - **HFRS strains**: 1-15% depending on strain - **Puumala virus** (mildest): <1% ## Long-Term Effects in Survivors **Recovery Period:** - Initial diuretic phase 1-2 weeks - Gradual strength return over months - Most patients return to baseline by 3-6 months **Possible Sequelae:** - Reduced exercise tolerance - Some pulmonary function abnormalities - Fatigue - Most fully recover ## Prevention **The Key to Reducing Hantavirus is Prevention:** **Personal Protection:** - **Avoid contact** with rodents and rodent excretions - **Wear gloves and mask** when cleaning potentially infested areas - **Wet cleaning methods** rather than sweeping/vacuuming - **Use bleach solutions** (1:10) to disinfect surfaces - **Open windows** to ventilate before cleaning enclosed spaces **Home Protection:** - **Seal entry points** to keep rodents out - **Proper food storage** in rodent-proof containers - **Eliminate harborage** — clutter, debris piles - **Set traps appropriately** - **Professional pest control** for significant infestations **Travel Precautions:** - **Avoid rural rustic accommodations** in endemic areas when possible - **Inspect sleeping areas** for rodent activity - **Store food properly** during travel - **Use commercial accommodations** with active rodent control **Occupational Safety:** - **Proper PPE** for high-risk occupations - **Decontamination protocols** - **Training programs** - **Medical surveillance** **For Andes Virus (Person-to-Person Risk):** - **Healthcare PPE** for confirmed cases - **Household isolation** during illness - **Contact tracing** for known cases - **Avoid close contact** with symptomatic individuals from endemic areas ## When to Seek Medical Attention **Seek IMMEDIATE medical care for:** - Flu-like symptoms following rodent exposure or travel to endemic areas - Symptoms developing 1-6 weeks after potential exposure - Severe muscle aches, especially in thighs/back - Any respiratory symptoms following prodromal phase - Healthcare workers who cared for confirmed cases who develop symptoms