Hantavirus pulmonary syndrome advances through two distinct stages. In the first stage, you may experience flu-like signs and symptoms that may include:

• Fever and chills
• Headaches and muscle aches
• Vomiting, diarrhea or abdominal pain

In its early stages, hantavirus infection is difficult to distinguish from influenza, pneumonia or other viral conditions. After four to 10 days, more-serious signs and symptoms begin. They typically include:

• A cough that produces secretions
• Shortness of breath
• Fluid accumulating within the lungs
• Low blood pressure
• Reduced heart efficiency

Each type of hantavirus has a preferred rodent carrier. The deer mouse is the primary carrier of the virus responsible for most cases of hantavirus pulmonary syndrome in North America. Other hantavirus carriers include the white-tailed mouse, cotton rat and rice rat.

Inhalation: Main route of transmission

Hantaviruses are transmitted to people primarily through the aerosolization of viruses shed in infected rodents' droppings, urine or saliva. Aerosolization occurs when a virus is kicked up into the air, making it easy for you to inhale. For example, a broom used to clean up mouse droppings in an attic may nudge into the air tiny particles of feces containing hantaviruses, which you can then easily inhale.

After you inhale hantaviruses, they reach your lungs and begin to invade tiny blood vessels called capillaries, eventually causing them to leak. Your lungs then flood with fluid, which can trigger any of the respiratory problems associated with hantavirus pulmonary syndrome.

Person-to-person transmission

People who become infected with the North American strain of hantavirus pulmonary syndrome aren't contagious to other people. However, certain outbreaks in South America have shown evidence of being transmitted from person to person, which illustrates variation across strains in different regions.

Hantavirus pulmonary syndrome is most common in rural areas of the western United States during the spring and summer months. Hantavirus pulmonary syndrome also occurs in South America and Canada. Other hantaviruses occur in Asia, where they cause kidney disorders rather than lung problems.

The chance of developing hantavirus pulmonary syndrome is greater for people who work, live or play in spaces where rodents live. Factors and activities that increase the risk include:

• Opening and cleaning long unused buildings or sheds
• Housecleaning, particularly in attics or other low-traffic areas
• Having a home or workspace infested with rodents
• Having a job that involves exposure to rodents, such as construction, utility work and pest control
• Camping, hiking or hunting

Hantavirus pulmonary syndrome can quickly become life-threatening. As the lungs fill with fluid, breathing becomes more and more difficult. Blood pressure drops and organs begin to fail, particularly the heart. Depending on the hantavirus strain, the mortality rate for the North American variety of hantavirus pulmonary syndrome can be more than 30%.