Hantaviruses are found in the saliva, urine, and droppings of infected rodents, which show no signs of illness.

In the United States, at least four hantaviruses are known to cause hantavirus pulmonary syndrome (HPS). Each hantavirus is carried by a specific rodent:

• Sin Nombre virus (SNV) is carried by the deer mouse and is found throughout North America. SNV causes the majority of HPS cases in the U.S.
• New York virus is carried by the white-footed mouse and is found mostly in southern New England and the mid-Atlantic, southern, midwestern, and western states.
• Bayou virus is carried by the rice rat and is found mostly in Louisiana and Texas.
• Black Creek Canal virus is carried by the cotton rat and is found mostly in Florida.

Other rodents may carry hantaviruses, but they have not been identified. In addition, other related viruses cause a spectrum of diseases called hemorrhagic fever with renal syndrome (HFRS). Many of the first symptoms of HFRS resemble hantavirus pulmonary syndrome, but the later symptoms of HFRS may include high fever, kidney failure, and bleeding disorders.