Hantavirus Pulmonary Syndrome --- Vermont, 2000

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In 1993, an outbreak of an unexplained pulmonary illness occurred in the southwestern United States. This outbreak led to the first description of hantavirus pulmonary syndrome (HPS), a rodentborne hantaviral infection. Hantaviruses have been found in rodents in rural areas throughout the United States, but most infection has occurred in the southwest (1,2). This report describes the first HPS case in Vermont and underscores the importance of preventing exposure to peridomestic rodents and recognizing the signs and symptoms of HPS.

On February 17, 2000, a 61-year-old previously healthy Vermont resident was hospitalized following three syncopal episodes and 1 week of chills, fever (<102 F ([<39 C]), nausea, vomiting, anorexia, and right knee pain. Upon admission, the patient's temperature was 99.3 F (37.4 C), pulse rate was 90 beats per minute, and blood pressure was 135/90 mm Hg. On examination, the lungs were clear to auscultation, a 2 x 2 cm nontender lymph node was identified at the angle of the left jaw, and a mild effusion was present in the right knee. A complete blood count included a hematocrit of 55.6% (normal: 36%--52%), a platelet count of 99,000/mm³ (normal: 150,000--400,000/mm³), and a white blood cell count of 6900/mm³ (normal: 4,000--10,000/mm³) with 83% granulocytes, 8.0% lymphocytes, and 8.0% monocytes. Chest radiographs were clear without infiltrates. However, 1 day after admission, the patient's condition deteriorated with onset of respiratory failure, profound hypoxemia, and hypotension requiring mechanical ventilation. Subsequent chest radiographs revealed bilateral interstitial edema consistent with acute respiratory distress syndrome (ARDS). The patient also developed disseminated intravascular coagulation and renal insufficiency (peak blood urea nitrogen: 62 mg/dL [normal: 7--18 mg/dL] and peak creatinine 2.9 mg/dL [normal: 0.5--1.4 mg/dL]). After 23 days in the hospital, including 16 days in intensive care, the patient was discharged with a diagnosis of ARDS and sepsis of uncertain etiology.

During the 2 months preceding hospitalization, the patient, who resided in a house on four rural acres, had cleaned a mouse nest from a woodpile, observed mice in the basement, and trapped two mice under the kitchen counters. The patient's reported symptoms and exposure to rodents led to the collection of two serum specimens on April 6 and 17, which were submitted to CDC for hantavirus diagnostic testing. Using an enzyme-linked immunosorbent assay, immunoglobin M (IgM), and immunoglobin G (IgG), antibodies to Sin Nombre virus were detected; these antibodies indicated recent hantavirus infection (3).

During an onsite investigation conducted April 21 by the Vermont Department of Health, mice droppings were observed under the kitchen counter and in the cellar. In April and May, the wildlife services program of the U.S. Department of Agriculture trapped rodents within a 5-mile radius of the patient's house to estimate the prevalence of hantavirus infection in local rodent populations. After 1632 trapnights (i.e., number of traps times the number of nights), 46 rodents were captured, including six deer mice (Peromyscus maniculatus), 13 white-footed mice (P. leucopus), 21 woodland jumping mice (Napaeozapus insignis), one meadow jumping mouse (Zapus hudsonius), four chipmunks (Tamias striatus), and one vole (Microtus sp.). Because cases of hantavirus infection are new among humans and the rodent reservoir is not well described, especially in the northeast, most of these rodents were tested serologically at CDC for hantaviral antibodies. Among 43 rodents tested, two of five deer mice were positive for hantaviral antibodies; all other rodents were negative.

Reported by: W Craig, MD, Plainfield Health Center, Plainfield; K Cook, MD, J Carney, MD, S Schoenfeld, MSPH, B Wilcke, PhD, Vermont Dept of Health. T Algeo, Wildlife Svcs Program, Animal and Plant Health Inspection Svc, US Dept of Agriculture. Special Pathogens Br, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC.

Editorial Note:

This report describes the first case of HPS acquired in New England; only 15 (5%) of the 284 cases confirmed by CDC have occurred east of the Mississippi River. Hantaviruses known to cause HPS in the United States include Sin Nombre, New York, Monongahela, Bayou, and Black Creek Canal viruses. Because rodent species that host one or more viruses are found throughout the contiguous United States, sporadic cases may occur anywhere on the mainland (4). Among approximately 115 (75%) of 153 patients with documented exposure to rodents or rodent droppings, exposure had occurred in and around the house. In Vermont, the primary rodent reservoirs of these hantaviruses are likely to be the deer mouse (P. maniculatus) and the white-footed mouse (P. leucopus). Other rodent species known to carry HPS-associated hantaviruses include the rice rat (Oryzomys palustris) and cotton rat (Sigmodon hispidus) (5,6).

Although it was not reported in the 1993 outbreak (2), renal impairment is a component of disease associated with Sin Nombre viral infection and related viruses, as indicated in the case in this report. Renal impairment also has been predominant in disease caused by Black Creek Canal and Bayou viruses. Another component recognized since the first outbreak is disease accompanied by frank hemorrhage (7).

The case described in this report demonstrates the importance of considering hantavirus infection when diagnosing an unexplained acute respiratory distress syndrome or bilateral interstitial pulmonary infiltrates (8). Although the Vermont patient had symptoms unrelated to hantavirus infection (e.g., a nontender lymph node and knee pain), other signs, symptoms, and environmental circumstances suggested HPS. When patients may have been exposed to rodents or rodent droppings, especially in and around the house, clinicians should request serologic testing to detect hantavirus-specific IgM and IgG. Information about testing is available from local or state health departments, and testing is available at CDC. Additional information about hantaviruses and HPS is available at http://www.cdc.gov/ncidod/diseases/hanta/hantvrus.htm; telephone (877) 232-3322 or (404) 639-1115.

References

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