Diseases & Conditions

Hantavirus pulmonary syndrome

Hantavirus pulmonary syndrome is an infectious disease characterized by flu-like symptoms that progress rapidly to potentially life-threatening breathing problems.

Several types of hantavirus can cause hantavirus pulmonary syndrome. They are carried by several types of rodents, particularly the deer mouse. You become infected primarily by breathing air infected with hantaviruses that are shed in rodent urine and droppings.

Because treatment options are limited, the best protection against hantavirus pulmonary syndrome is to avoid rodents and their habitats.

Hantavirus pulmonary syndrome advances through two distinct stages, with the first signs and symptoms appearing between one and five weeks after exposure to a hantavirus.

The early stage
Signs and symptoms such as fever, fatigue and chills are early indicators of a hantavirus infection. Within several days, nausea, vomiting, abdominal pains and headaches may develop. In its early stages, hantavirus infection is difficult to distinguish from influenza, pneumonia or other viral conditions.

Signs and symptoms of early-stage infection include:

• Fatigue
• Fever
• Chills
• Muscle aches, especially in large muscle groups, such as your thighs, hips and back
• Bubbling or rattling sounds in your lungs (rales)
• Abnormally fast breathing (tachypnea)
• Abnormally fast heartbeat (tachycardia)
• Headaches
• Dizziness
• Nausea
• Vomiting
• Diarrhea
• Abdominal pain

The cardiopulmonary stage
A cough often indicates that the hantavirus infection has progressed into the cardiopulmonary stage, in which the capillaries of your lungs begin to weaken and leak fluid. Shortness of breath and respiratory troubles can follow.

Symptoms or signs of the cardiopulmonary stage include:

• A cough that produces secretions
• Reduction of oxygen (hypoxia or hypoxemia) and a buildup of carbon dioxide (hypercarbia) and acid (acidemia) in your blood
• Shortness of breath
• Respiratory insufficiency (shock) or failure
• Buildup of fluid in your lungs (pulmonary edema)
• Acute respiratory distress syndrome (ARDS), in which your lungs' ability to transfer oxygen to your blood is severely impaired
• Multiorgan failure
• Low blood pressure (hypotension)
• Slower or faster than normal heartbeat (arrhythmia)

When to see a doctor
If you've been around rodents or rodent droppings and have symptoms of fever, chills, muscle aches or any difficulties breathing, seek immediate medical attention. Be sure to tell your doctor you have had exposure to rodents or their droppings.

Each type of hantavirus has a preferred rodent carrier. The deer mouse is the primary carrier of the Sin Nombre virus, which is 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: The 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.

Other routes of transmission
Although rare, there are other methods of hantavirus transmission. You can become infected after receiving a rodent bite or after eating food containing rodent excrement. Person to person transmission of this disease is rare.

Blood tests are the main method for diagnosing hantavirus pulmonary syndrome. These are laboratory tests that analyze samples of your blood for the presence of certain antibodies that your body produces as a defense against disease-causing agents (pathogens). For people with hantavirus infection, antibodies of the IgM and IgG classes are nearly always present in the blood by the time signs and symptoms appear.

Because hantavirus pulmonary syndrome can resemble many other illnesses, your doctor may order further laboratory tests — such as cultures, urinary antigen tests or other blood tests — to rule out other conditions. For example, symptoms of hantavirus pulmonary syndrome can resemble influenza, Legionnaires' disease, pneumonic plague and Q fever.

Specific treatment options for hantavirus pulmonary syndrome are limited. But the prognosis improves with early recognition, immediate hospitalization and adequate support for breathing.

Two hantavirus treatment options are:

• Supportive therapy. People with severe cases need immediate treatment in an intensive care unit. Assisted respiration, whether through intubation or mechanical ventilation, can help with breathing and ward off pulmonary edema. Intubation involves placing a breathing tube through your nose, mouth or trachea to help keep your airways open and functioning.
• Blood oxygenation. In extremely severe cases of pulmonary distress, you'll need a method called extracorporeal membrane oxygenation to help ensure you retain a sufficient supply of oxygen. This involves continuously pumping your blood through a machine that removes carbon dioxide and adds oxygen. The resulting oxygenated blood is then returned to your body.

The antiviral medication called ribavirin effectively reduces the risk of complications from a type of hantavirus found in China. In the U.S. and Canada, studies of ribavirin in people in the cardiopulmonary stage of hantavirus infection showed no benefit. Researchers are evaluating whether ribavirin treatment might be beneficial if started before cardiopulmonary symptoms develop.