Genus of pneumonia and {{link=hemorrhagic fever">hemorrhagic fevers .
Carried by rodents, they spread to humans directly or by inhalation but apparently are not transmitted from one person to another. An outbreak in the 1990s in the southwestern U.S. caused a mysterious, often fatal, flulike illness with rapid respiratory failure in previously healthy adults. The culprit was a hantavirus type carried by mice and not previously associated with human illness in the U.S.