How is hantavirus transmitted?
The Rodent Connection

So just how do people get hantavirus pulmonary syndrome (HPS)? It all starts with rodents, like the deer mouse and cotton rat, which carry hantaviruses.

The basic transmission cycle

The short story is that some rodents are infected with a type of hantavirus that causes HPS. In the United States, deer mice (plus cotton rats and rice rats in the southeastern states and the white-footed mouse in the Northeast) are the rodents carrying hantaviruses that cause hantavirus pulmonary syndrome.

These rodents shed the virus in their urine, droppings and saliva. The virus is mainly transmitted to people when they breathe in air contaminated with the virus.

This happens when fresh rodent urine, droppings or nesting materials are stirred up. When tiny droplets containing the virus get into the air, this process is known as " aerosilzation."

There are several other ways rodents may spread hantavirus to people:

• If a rodent with the virus bites them, the virus may be spread this way—but this is very rare.
  
• Researchers believe that you may be able to get the virus if you touched something that had been contaminated with rodent urine, droppings or saliva, and then touched your nose or mouth.
  
• Researchers also suspect that if virus-infected rodent urine, droppings or saliva contaminates food that you eat, you could also become sick.

That is another reason why disinfecting rodent-infested areas is so important in preventing transmission of the virus.

Transmission can happen anyplace that infected rodents have infested. (Remember, by "carrier rodent" we mean deer mice plus cotton rats and rice rats in the Southeastern states, and the white-footed mouse in the Northeast. Common house mice do not carry hantavirus.) This could be barns or sheds or other outbuildings, warehouses or summer cottages closed up for the season. But carrier rodents infest homes as well!

Therefore, the most sensible way to avoid contact with rodents is to prevent rodents from infesting the places where you live and work, and to follow safety precautions if you do stumble into a rodent-infested area. The prevention section of this web site details all of this for you!

Could you get the hantavirus from another person?

Remember, the types of hantavirus that cause HPS in the United States stop at the person who has been infected—they cannot be transmitted from one person to another. For example, you cannot get the virus from touching or kissing a person who has the disease, or from a health care worker who has treated someone with the disease. Finally, you cannot get the virus from a blood transfusion in which the blood came from a person who came down with hantavirus pulmonary syndrome and survived.

Could you get hantavirus from animals other than rodents, or from insects? What about pets?

No—researchers do not believe that the hantaviruses causing HPS in the United States are transmitted by any other types of animals besides certain species of rodents. This would include farm animals like cows, chickens or sheep and insects like mosquitoes. Dogs and cats are not known to carry hantavirus.  However, they may bring infected rodents into contact with people if they catch infected rodents and carry them home. Guinea pigs, hamsters, gerbils and other such pets are not known to carry hantavirus.

Summing up:
How hantavirus is transmitted

• exposure to infected rodent (deer mouse, white-footed mouse, cotton rat, rice rat)
• rodent saliva/droppings dry up, are "aerosolized" and breathed in
• no transmission from other people, in the United States
• no known transmission from other animals or insects

1999, Special Pathogens Branch
Division of Viral and Rickettsial Diseases
National Center for Infectious Diseases
The Centers for Disease Control and Prevention (CDC)
U.S. Department of Health and Human Services