Among the NewWorld hantaviruses ( Sin nombre virus, Andes, Bayou, Black Creek Canal, New York, and Monon- gahela), Sin nombre virus (SNV) was first described in 1993 as the cause of a cluster outbreak of severe pneumonia with respiratory failure or hantavirus pulmonary syndrome (HPS) in 24 young patients - 18 of whom died (CFR = 76%) - in the Four Corners region of the southwestern US, where the borders of Arizona, Colorado, New Mexico, and Utah meet. 20 All of the New World hantaviruses target the heart and lungs and can cause HPS. 6 Only Andes virus, which is endemic in South America, is capable of human-to-human transmission. 6 Although the US hantaviruses cause HPS and not HFRS like the Old World hantaviruses, both of the Southeastern hantaviruses, Bayou virus, and Black Creek Canal virus may cause HPS associated with clinical find- ings similar to Eurasian strain-caused HFRS, including severe myositis, renal insufficiency with elevated creatinine and blood urea nitrogen (BUN) levels, and intra-alveolar hemorrhage. 8,9 Humans become infected by inhalation of aerosolized virions from rodent excreta, or, less commonly, by rodent bites (1 of 10 cases in the Yosemite HPS outbreak), often during sweeping and clean-up of rodent habitats within closed spaces. 5 Following an incubation period of 9-33 days (median=14-17 days), patients with HPS develop a prodro- mal febrile syndrome with chills, headache, myalgias, and vomiting followed within three to seven days by a cardio- pulmonary phase with cough, dyspnea, pulmonary edema, and respiratory failure requiring mechanical ventilation. 6 Associated hematological findings include hemoconcentra- tion, thrombocytopenia, and left-shifted granulocytosis. 15 An early, pathognomonic immunological response in HPS is the appearance of circulating immunoblasts, which herald the end of the prodromal phase and the onset of the cardio- respiratory phase. 23 Hypoalbuminemia and elevated hepatic enzymes may occur in severe cases. 15 Since all available serologic tests for the diagnosis of HPS are broadly cross-reactive with all of the New World hantaviruses, specific hantavirus identification requires polymerase chain reaction (PCR) with sequencingwith acute specimens collected early in the illness and shipped to refer- ence laboratories frozen to preserve RNA for analysis. 21 Since there is no vaccine or specific antiviral therapy - including ribavirin - for HPS, only early diagnosis and intensive sup- portive care, potentially including extracorporeal membrane oxygenation (ECMO) and nitric oxide (NO) administration, will reduce the high CFRs from HPS. 15 Clinicians should always consider a diagnosis of HPS in persons with febrile illnesses that progress rapidly to respiratory insufficiency following rodent exposures in enclosed spaces. Eradicating all rodent reservoir hosts for both pathogen- ic leptospires and hantaviruses is both impractical, because of the widespread distribution of rodents, and undesirable, because of the importance of rodents as insectivores and prey for larger predators in the ecosystem. 24 The best and most effective strategies for the control and prevention of rodent-borne infectious diseases include storing all unre-
frigerated foods, including pet foods in thick plastic, glass, or metal containers with tight-fitting lids; limiting contact with all wild and peridomestic rats and mice; avoiding all contact with rodent excreta; safely disposing of all rodent excreta; and modifying the built environment to deter rodents from frequenting and colonizing households and workplaces. 24 Only spring-loaded traps that kill rodents should be deployed, as live and sticky traps do not kill rodents which can bite humans during disposal, transmit- ting hantaviruses and creating open wounds for potential leptospirosis transmission. 24 While struggling to get free of non-lethal traps, rodents chronically infected with lepto- spires or hantavivuses may urinate and/or emit infectious aerosols contaminating enclosed spaces. 24 All areas inhab- ited by rodents should be cleaned with mops wetted with dilute bleach solutions rather than swept or vacuumed, which could create infectious aerosols. Interested readers are referred to the MMWR Recommendations and Reports Series, No. 9, 2002, for a listing of all CDC-recommended strategies to limit household exposures to rodents, to rodent-proof households and workplaces, to select the best disinfecting solutions to clean-up rodent excreta and nesting materials, and to safely dispose of dead rodents and their nests. 24 CONCLUSIONS Healthcare providers should maintain high levels of suspicion for leptospirosis in patients developing febrile illnesses after contaminated freshwater exposures dur- ing flooding events or freshwater recreational events; and public health officers should immediately promote heightened awareness of leptospirosis outbreaks among all flood-affected populations. Clinicians should consider a diagnosis of hantavirus pulmonary syndrome in all persons with febrile illnesses that progress rapidly to respiratory insufficiency following rodent exposures in enclosed spaces. Public health educational strategies should encourage lim- iting human contact with all wild and peridomestic rats and mice, avoiding all contact with rodent excreta, safely disposing of all rodent excreta, and modifying the built environment to deter rodents from colonizing households and workplaces. The causative agents for leptospirosis and HPS are widely distributed in the US and will continue to cause sporadic outbreaks of potentially fatal illnesses, often precipitated by cyclical climatic conditions associated with heavy rainfall and flooding. REFERENCES 1. Outbreak of acute febrile illness among athletes participating in triathlons—Wisconsin and Illinois, 1998. Morb Mort Week Rep 1998; 47: 585-588. 2. Pavli A, Maltezou HC. Travel-acquired leptospirosis. J Travel Med 2008; 15: 447-453. 3. Outbreak of leptospirosis amongwhite-water rafters—Costa Rica, 1996. Morb Mort Week Rep 1997; 46: 577-579. 4. Brief Report: Leptospirosis after flooding of a university campus—
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