Conjunctival suffusion is rarely seen in HPS, in North America but facial flushing is commonly related to the HPS in the Patagonian region of South America. After 4 to 5 days, pulmonary symptoms usually appear, which characterizes the second phase. Hypotension and pulmonary edema evolve rapidly, usually in 4 to 24 hours. Shock is then manifested by hypotension, oliguria and delirium. Most patients present a serious depression of the myocardium, with extremely low cardiac indices.
Spontaneous diuresis indicates the onset of the diuretic phase.
It is followed by convalescent phase. Some patients infected by the Black Creek Canal hantavirus as well as the Bayou and Andes viruses frequently develop a more severe renal failure, requiring hemodyalisis. Virtually all confirmed HPS patient will have detectable amounts of IgM in the first or second serum sample taken after hospitalization. PCR may be used to establish diagnosis, however it is only available in selected research laboratories. This technique should, then, be used to determine viral genotype.