Hantavirus pulmonary syndrome
Hantavirus pulmonary syndrome: Excerpt from Handbook of Diseases
Mainly occurring in the southwestern United States, Hantavirus pulmonary syndrome was first reported in May 1993. The syndrome, which rapidly progresses from flulike symptoms to respiratory failure and, possibly, death, is known for its high mortality.
The Hantavirus strain that causes disease in Asia and Europe — mainly hemorrhagic fever and kidney disease — is distinctly different from the one described in North America.
Causes
A member of the Bunyaviridae family, the genus Hantavirus (first isolated in 1977) is responsible for Hantavirus pulmonary syndrome. Disease transmission is associated with exposure to infected rodents, the primary reservoir for this virus.
Data suggest that the deer mouse is the main source, but pinion mice, brush mice, and western chipmunks in proximity to humans in rural areas are also sources.
Infected rodents manifest no apparent illness but shed the virus in feces, urine, and saliva. Human infection may occur from inhalation, ingestion (of contaminated food or water, for example), contact with rodent excrement, or rodent bites. Transmission from person to person or by mosquitoes, fleas, or other arthropods has not been reported.
Hantavirus infections have been documented in people whose activities are associated with rodent contact, such as farming, hiking, or camping in rodent-infested areas, and occupying rodent-infested dwellings.
Signs and symptoms
Noncardiogenic pulmonary edema distinguishes the syndrome. Common chief complaints include myalgia, fever, headache, nausea, vomiting, and cough. Respiratory distress typically follows the onset of a cough. Fever, hypoxia and, in some patients, serious hypotension typify the hospital course.
The first signs of illness appear within 1 to 5 weeks of exposure, especially fever and muscle aches. This is followed by coughing and shortness of breath. At this point, the disease progresses rapidly, necessitating ventilation within 24 hours.
Other signs and symptoms include a rising respiratory rate (less than 28 breaths/ minute) and an increased heart rate (greater than 120 beats/minute).
Diagnosis
Despite efforts to identify clinical and laboratory features that distinguish Hantavirus pulmonary syndrome from other infections with similar features, diagnosis is based on clinical suspicion along with a process of elimination developed by the Centers for Disease Control and Prevention (CDC) with the Council of State and Territorial Epidemiologists. (See Screening for Hantavirus pulmonary syndrome.)
Laboratory tests usually reveal an elevated white blood cell count with a predominance of neutrophils, myeloid precursors, and atypical lymphocytes; elevated hematocrit; decreased platelet count; prolonged partial thromboplastin time; and a normal fibrinogen level.
Usually, laboratory findings demonstrate only minimal abnormalities in renal function, with serum creatinine levels no higher than 2.5 mg/dl.
Chest X-rays eventually show bilateral diffuse infiltrates in almost all patients (findings consistent with adult respiratory distress syndrome).
Treatment
Primarily supportive, treatment consists of maintaining adequate oxygenation, monitoring vital signs, and intervening to stabilize the patient’s heart rate and blood pressure.
Drug therapy includes administering vasopressors, such as dopamine or epinephrine, for hypotension. Fluid volume replacement may also be ordered (with precautions not to overhydrate the patient).
I.V. ribavirin early in the illness has shown benefit.
Special considerations
❑ Assess the patient’s respiratory status and arterial blood gas values often.
❑ Maintain a patent airway by suctioning. Ensure adequate humidification, and check ventilator settings frequently.
❑ In the patient with hypoxemia, assess neurologic status frequently along with heart rate and blood pressure.
❑ Administer drug therapy, and monitor the patient’s response.
❑ Monitor the patient’s serum electrolyte levels, and correct imbalances as appropriate.
❑ Provide I.V. fluid therapy based on the results of hemodynamic monitoring.
❑ Provide emotional support for the patient and his family.
Clinical tip Report cases of Hantavirus pulmonary syndrome to the state health department.
❑ Provide prevention guidelines. (Until more is known about Hantavirus pulmonary syndrome, preventive measures focus on rodent control.)
Pictures
Book Source Details
- Book Title: Handbook of Diseases
- Author(s): Springhouse
- Year of Publication: 2003
- Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
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