EPO and hantavirus infectious disease: The significantly elevated hemoglobin level in this case may suggest absolute erythrocytosis caused by, for example, chronic diseases such as heart failure or chronic obstructive pulmonary disease (COPD), hemoglobin anomalies, abuse of erythropoietin or polycythemia, or relative erythrocytemia due to conditions such as polyuria, exsiccosis caused by increased fever-induced perspiration, or capillary leak which is frequently found in systemic infections (e.g. malaria, leptospirosis, hantavirus infection).