Journal of the Louisiana State Medical Society
Table 1: Summary of the laboratory-confirmed cases of hantavirus pulmonary syndrome cases, United States, 1993-2013. 10 US hantavirus species Rodent reservoirs: Common name (Latin name) Number of US cases States of occurrence (unknown for 28 cases) Sin nombre (Spanish for “without a name”) Deer mouse ( Peromyscus maniculatus ) 658 Every US state except MI, OH, NH, CT, MA,
RI, NJ, DL, ML, MO, AR, KY, TN, LA, MS, AL, GA, FL, SC
Bayou
Marsh rice rat ( Oryzomys palustris )
5
TX, LA
Monongahela
Deer mouse ( Peromyscus maniculatus )
4
PA, WV
New York
White-footed mouse ( Peromyscus leucopus ) Hispid cotton rat ( Sigmodon hispidus )
2
NY
Black Creek Canal
1
FL
Hantavirus Outbreak: Hantavirus Pulmonary Syndrome - California, 2012 (Adapted from MMWR , November 23, 2012) 5
myscus maniculatus , in states west of the Mississippi River. 6 All 624 HPS cases in the US during the period 1993-2004 are depicted by cumulative case counts for each state in Figure 2. 6 Although the deer mouse ranges throughout the western US, it is not indigenous to the southeastern US or to the Atlantic seaboard states. 6 The few cases of HPS de- scribed in these areas (n=12) were caused by other species of hantaviruses, each having different, preferred rodent reservoirs (Table 1). 6 Bayou virus with a rodent reservoir in the marsh rice rat, Oryzomys palustris , was responsible for the second largest number of HPS cases in the US after Sin nombre virus; four in Texas and one in Louisiana in 1995 (Figure 3). 7-11 In 1996, Khan and co-investigators reported a fatal case of HPS associated with renal insufficiency in a 33-year-old Florida man caused by a newly identified hantavirus, the Black Creek Canal (BCC) virus (Figure 4). 8 A rodent reservoir in the indigenous cotton rat, Sigmodon hispidus , was suspected and established initially by a 13% seroprevalence of antihantaviral IgG antibodies in trapped cotton rats; it was later confirmed by the detection of BCC virus RNA in seropositive rats by reverse transcriptase- polymerase chain reaction (RT-PCR) assay. 8,12,13 Ravkov and co-investigators emphasized that the combination of the genetically diverse genome of the Black Creek Canal virus, the high seroprevalence of subclinical chronic infection in cotton rats, and the vast distribution range of the cotton rat in the Americas compared to the limited ranges of the deer mouse and the rice rat could pose a significant public health threat throughout the Americas (Figure 4). 14 Infectedmice copiously shed hantavirus in urine, feces, and saliva into the environment, with virions remaining viable and infective for up to 15 days. 15 All outdoor rodent populations are extremely sensitive to climatic conditions and will seek shelter, food, and water whenever forced into the built environment by heavy precipitation and floodwaters. 16 Engelthaler and co-investigators studied the environmental patterns associated with the initial HPS outbreak in the Four Corners region in 1993. 16 The investiga-
On August 16, 2012, after a mild winter and a rainy spring and summer, the California Department of Pub- lic Health in conjunction with the CDC announced two serologically-confirmed cases of hantavirus pulmonary syndrome (HPS) in two California residents who had stayed overnight in cabins in Yosemite National Park. Follow- ing this outbreak, the National Park Service contacted all 260,000 overnight visitors to Yosemite during the period, June 1-September 17, 2012; provided information on the transmission and presenting clinical manifestations of HPS; and requested immediate health status responses. This surveillance detected two cases of HPS in non-residents of California who had returned to their home states of Penn- sylvania and West Virginia after their summer vacations to Yosemite. By October 30, 2012, 10 cases of HPS with three deaths were confirmed among overnight visitors to the park during the period, June 1, 2012 to August 28, 2012; nine of whom spent at least one night in the same park village of 91 cabins. Since HPS was first described in California in 1994, there had been 58 cases of HPS in the state; only two of those were visitors to Yosemite. Environmental investigation of the cabins in the park village detected evidence of deer mouse infestation between the exterior and interior walls of all 91 cabins. In addition, several regional area deer mice ( Peromyscus maniculatus ) were seropositive for Sin nombre virus, the causative agent of HPS throughout the western US. The park’s cabin village was closed indefinitely. The case fatality rate (CFR) for HPS in the Yosemite outbreak was 33%, which was consistent with the current national CFR for HPS of 36%. 5 Hantaviruses in the US: 1993-Present Over the past 20 years, 624 cases of HPS have been described, with most cases (n=612, 98%) caused by the Sin nombre virus and its rodent reservoir in deer mice, Pero-
188 J La State Med Soc VOL 166 September/October 2014
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