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Infectious Disease and Microbiology: Hantavirus Pulmonary Syndrome (HPS)
Hantavirus pulmonary syndrome (HPS) is a severe and life-threatening cardiopulmonary disease caused by hantaviruses, most commonly the Sin Nombre virus in North America. First recognized in 1993 in the southwestern United States, the disease is associated with a high mortality rate and rapid clinical deterioration. It primarily affects previously healthy individuals who are exposed to infected rodents.
Epidemiologically, HPS is rare but has been reported in multiple regions across the Americas. Its occurrence is closely linked to the population dynamics of rodents, particularly deer mice and other species such as cotton rats and white-footed mice. Human infection typically results from inhalation of aerosolized particles contaminated with rodent urine, feces, or saliva. Individuals at higher risk include farmers, construction workers, campers, and those cleaning rodent-infested buildings. Although person-to-person transmission is extremely uncommon, it has been reported in certain regions with specific strains such as the Andes virus.
The pathophysiology of HPS involves viral infection of endothelial cells, especially within the lungs, leading to increased vascular permeability. This results in capillary leak syndrome, pulmonary edema, and impaired oxygen exchange. The disease is driven largely by the host immune response rather than direct viral destruction of tissues, leading to pneumonitis, shock, and respiratory failure.
Clinically, the illness begins with a prodromal phase lasting several days, characterized by nonspecific symptoms such as fever, myalgia, fatigue, headache, and sometimes gastrointestinal complaints. This is followed by an abrupt cardiopulmonary phase marked by cough and rapidly progressive shortness of breath, often leading to respiratory failure within a short time. Physical findings include tachypnea, hypoxia, pulmonary crackles, and signs of circulatory shock. Death may occur due to severe hypoxia, shock, or cardiac arrhythmias.
Laboratory evaluation typically reveals leukocytosis with a left shift, thrombocytopenia, hemoconcentration, and atypical lymphocytes. Elevated liver enzymes, creatine phosphokinase, and lactate dehydrogenase are also common. Imaging studies such as chest X-ray or CT scan demonstrate interstitial infiltrates, pulmonary edema, and pleural effusions. Diagnosis is confirmed through serologic testing detecting hantavirus-specific IgM or rising IgG titers, PCR identification of viral RNA, or immunohistochemical detection of viral antigens in tissue samples.
Management of HPS is primarily supportive, as no proven antiviral therapy exists. Patients often require hospitalization and close monitoring, with many needing intensive care, oxygen supplementation, or mechanical ventilation. Broad-spectrum antibiotics are usually started initially until other causes of severe pneumonia are excluded. In critical cases, advanced supportive therapies such as extracorporeal membrane oxygenation (ECMO) may be employed. Prevention relies on minimizing exposure to rodents and their excreta, as no vaccine is currently available.
The prognosis of HPS is guarded, with mortality rates ranging from 35% to 40%, especially in patients with severe disease. Early recognition and aggressive supportive care improve survival. Major complications include acute respiratory distress syndrome, myocardial dysfunction, shock, and death.
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