Hantavirus pulmonary syndrome (HPS) is a rare but potentially fatal viral infection that is spread by mice and rats. People become infected through contact with hantavirus-infected rodents or their urine and droppings. The Sin Nombre hantavirus, first recognized in 1993, is one of several New World hantaviruses circulating in the US. Rodent control in and around the home remains the primary strategy for preventing hantavirus infection.
Signs and Symptoms for Hantavirus Pulmonary Syndrome (HPS)
Due to the small number of HPS cases, the incubation time is not precisely known, but, it appears that symptoms may develop between 1 and 5 weeks after exposure to fresh urine, droppings, or saliva of infected rodents.
Early symptoms include fatigue, fever and muscle aches, especially in the large muscle groupsâ€”thighs, hips, back, and sometimes shoulders. There may also be headaches, dizziness, chills, and abdominal problems, such as nausea, vomiting, diarrhea, and abdominal pain. About half of all HPS patients experience these symptoms.
Four to 10 days after the initial phase of illness, the late symptoms of HPS appear. These include coughing and shortness of breath and tightness in the chest as the lungs fill with fluid.
Where HPS is Found
Cases of HPS occur sporadically, usually in rural areas where forests, fields, and farms offer suitable habitat for rodents. Barns, outbuildings, and sheds are potential sites where people may be exposed to the virus. In the US and Canada, the Sin Nombre hantavirus is responsible for the majority of cases of HPS. The host of the Sin Nombre virus is the deer mouse present throughout the western and central US and Canada.
Several other hantaviruses are capable of causing HPS in the US. The New York hantavirus, hosted by the white-footed mouse, is associated with HPS cases in the northeastern US. The Black Creek hantavirus, hosted by the cotton rat, is found in the southeastern US.
Transmission of HPS
The hantaviruses that cause HPS in the United States are not known to be transmitted by any types of animals other than certain species of rodents. Dogs and cats are not known to carry hantavirus; however, they may bring infected rodents into contact with people if they catch such animals and carry them home. Guinea pigs, hamsters, gerbils, and rodents from pet stores are not known to carry hantavirus.
In the United States, deer mice, cotton rats, rice rats and the white-footed mouse are the reservoir of the virus. The 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.
When fresh rodent urine, droppings, or nesting materials are stirred up, tiny droplets containing the virus get into the air known as "airborne transmission".
How HPS is spread:
If a rodent with the virus bites someone, the virus may be spread to that person, but this type of transmission is rare.
Researchers believe that people may be able to get the virus if they touch something that has been contaminated with rodent urine, droppings, or saliva, and then touch their nose or mouth.
Researchers also suspect people can become sick if they eat food contaminated by urine, droppings, or saliva from an infected rodent.
The types of hantavirus that cause HPS in the United States cannot be transmitted from one person to another. You also cannot get the virus from a blood transfusion in which the blood came from a person who became ill with HPS and survived.
People at Risk for HPS
Anyone who comes into contact with rodents that carry hantavirus is at risk of HPS. Rodent infestation in and around the home remains the primary risk for hantavirus exposure. Even healthy individuals are at risk for HPS infection if exposed to the virus.
Any activity that puts you in contact with rodent droppings, urine, saliva, or nesting materials can place you at risk for infection. Hantavirus is spread when virus-containing particles from rodent urine, droppings, or saliva are stirred into the air. It is important to avoid actions that raise dust, such as sweeping or vacuuming. Infection occurs when you breathe in virus particles.
Opening or cleaning cabins, sheds, and outbuildings, including barns, garages and storage facilities that have been closed during the winter is a potential risk for hantavirus infections, especially in rural settings. Renovations of older homes is another potential source of exposure to the virus.
Cleaning in and around your own home can put you at risk if rodents have made it their home too. Many homes can expect to shelter rodents, especially as the weather turns cold. Please see our prevention information on how to properly clean rodent-infested areas.
Construction, utility and pest control workers can be exposed when they work in crawl spaces, under houses, or in vacant buildings that may have a rodent population.
Campers and hikers can also be exposed when they use infested trail shelters or camp in other rodent habitats.
Many people who have contracted HPS reported that they had not seen rodents or their droppings before becoming ill. Therefore, if you live in an area where the carrier rodents, such as the deer mouse, are known to live, take sensible precautions even if you do not see rodents or their droppings.
HPS in the United States
Through December 31, 2011, a total of 587 cases of Hantavirus Pulmonary Syndrome have been reported in the United States. Of these, 556 cases occurred from 1993-onward, following the initial identification of HPS, whereas 31 cases were retrospectively identified. Thirty-six percent of all reported cases have resulted in death.