Locally acquired hantavirus case in King County

Actions requested

• Be aware of a recent case of locally acquired Hantavirus Pulmonary Syndrome (HPS) reported in a resident of southeast King County.
• Maintain a high index of suspicion in patients with compatible clinical syndrome of HPS and risk factors for exposure to hantavirus. Patients present with a nonspecific clinical syndrome that progresses in severity.  
• Prodrome involves 3-5 days of symptoms that may include fatigue, fever, myalgias (large muscle groups), headache, dizziness, chills, nausea, vomiting, diarrhea, abdominal pain.  
• Pulmonary symptoms appear 4-10 days after prodrome, including cough, shortness of breath, rapidly progressive acute respiratory distress syndrome (ARDS), hemodynamic compromise. Chest imaging may show interstitial infiltrates.  
• Take a thorough history regarding exposures for hantavirus infection.  
• Risk factors include direct contact with rodents and exposure to areas with rodent infestation, nesting materials, and excreta. Deer mice are the primary carrier in Washington state.  
• Ask about the home, recreational or occupational activities, entering seasonally closed structures or buildings, infested automobiles. Consider air filters, vents, ducts, attics and crawl spaces. Because many HPS patients do not report explicit exposure to rodents, living or working in a heavily wooded, rural area should be considered a potential exposure risk.  
• Incubation varies between 1 – 8 weeks (average 2 weeks). 
• If HPS is suspected, repeat CBC and blood chemistry every 8-12 hours.  
• Platelet count <150,000 units is seen during the prodromal period in about 80% of cases. A dramatic decrease in platelet count may indicate transition from prodrome to pulmonary edema phase of illness.  
• A decrease in serum albumin and an increase in hematocrit may indicate a fluid shift from the patient's circulation into the lungs. 
• WBC count tends to be elevated with a marked left shift, frequently with atypical lymphocytes and immature precursor cells as high as 50%; this is usually seen at time of onset of pulmonary edema.  
• Obtain commercial hantavirus serology (Hantavirus Ab IgM and IgG) in patients suspected to have HPS and an exposure risk associated with hantavirus infection. Submission of all positive specimens to the Washington State Public Health Laboratory is required.  
• Consider consultation with an ID specialist and initiate supportive treatment. There are no effective antiviral therapies available. Person-to-person transmission has not been documented in North America.