Skip directly to search Skip directly to A to Z list Skip directly to navigation Skip directly to site content Skip directly to page options
CDC Home


Enzootic Cycle

mice in feild representing enzootic transmission of hantaviruses

Local enzootic transmission of hantaviruses occurs at low levels during periods of unfavorable environmental conditions.

Many hantaviruses are known to cause hantavirus pulmonary syndrome (HPS). Each virus has a single primary host. The most important hantavirus in the US is the Sin Nombre virus, hosted by the deer mouse.

Epizootic Cycle

mice in field representing epizootic cycle of hantavirus transmission

The virus is maintained and transmitted by host reservoir rodents by horizontal transmission (aggressive behavior, biting).

Favorable environmental conditions such as mild winters and summer rainfall may cause dramatic increases in rodent populations. More rodents become infected under crowded conditions. Deer mice may enter human structures in rural areas. Humans may become infected when they inhale airborne virus or come into direct contact with infected rodents or their urine, feces, or nests. Other mammal species (cats, dogs, coyotes) may be infected through contact with rodent hosts, but they are not known to transmit the virus.


CDC 24/7 – Saving Lives, Protecting People, Saving Money. Learn More About How CDC Works For You…
Contact Us:
  • Page last reviewed: August 29, 2012 The U.S. Government's Official Web PortalDepartment of Health and Human Services
Centers for Disease Control and Prevention   1600 Clifton Rd. Atlanta, GA 30329-4027, USA
800-CDC-INFO (800-232-4636) TTY: (888) 232-6348 - Contact CDC-INFO