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186 Hantavirus cardiopulmonary syndrome in the Americas
Introduction
Hantavirus cardiopulmonary syndrome (HCPS) is a viral zoonosis that may result in cardiogenic shock and respiratory failure with significant associated mortality. Hantavirus infection has been identified throughout much of North, Central, and South America. In the United States 586 cases of HCPS have been reported through December 2012 with a case-fatality rate of 35%. Half of these cases have been in the Four Corners area in the southwest. The incidence is even greater in South America, particularly in Argentina, Brazil, Chile, and Paraguay. In Chile alone, 795 cases have been reported through December 2012, with a case-fatality rate of 35%.
Virology
HCPS is caused by an infection with a hantavirus. There have been over 20 New World hantaviruses identified since their discovery in 1993. The New World hantaviruses differ from the Old World hantaviruses that cause hemorrhagic fever with renal syndrome (HFRS) and are found primarily in Asia and Europe. The most common hantavirus causing HCPS in Canada and the United States is Sin Nombre virus (SNV). Other hantaviruses that cause significant disease in Central and South America include Andes virus (ANDV) in Chile and Argentina, Choclo virus in Panama, and Laguna Negra virus in Paraguay. The hantaviruses are small single-stranded negative-sense RNA viruses that belong to the family Bunyaviridae, a family known to include other viruses that cause significant zoonotic illnesses.
Epidemiology
Hantavirus infection is spread to humans by a rodent reservoir. The primary rodent responsible for human transmission in North America is the deer mouse, Peromyscus maniculatus. These asymptomatic rodent hosts shed the virus in urine, feces, and saliva. Humans are thought to be infected when the aerosolized excreta are inhaled. People are exposed most often when they are cleaning enclosed areas where dried excreta are disturbed. Exposure through rodent bite has also been identified. Human-to-human transmission has only been documented with ANDV infections in Chile and Argentina. In Chile, approximately one-third of cases occur in household clusters, and most secondary cases in these clusters result from person-to-person transmission. In a recent prospective study of household contacts of patients with HCPS in Chile, Ferrés et al. reported a significantly higher risk of the development of HCPS in sex partners and other close household contacts as compared to members of the household who slept in different rooms and denied sexual contact.
Clinical syndrome
Most cases involve an individual with a prolonged exposure history, so it is often difficult to determine the exact incubation period. In a small series from Chile where individuals had brief periods of exposure to high-risk areas, the median incubation period between exposure and onset of clinical disease was 18 days, with a range of 11 to 32 days. Clinical disease begins with a febrile prodrome consisting of 2 days to a week of fevers and myalgias, often with associated headache, backache, abdominal pain, nausea, and diarrhea. After several days with nonspecific prodromal symptoms, the cardiopulmonary phase starts abruptly with cough and dyspnea. This stage of disease may be mild, requiring only supplemental oxygen, or severe, causing rapid pulmonary edema and respiratory failure requiring mechanical ventilation. Severe disease is also characterized by cardiogenic shock, hemoconcentration, and lactic acidosis that may result in profound shock, cardiac arrhythmias, and death. The cardiopulmonary phase
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