Sin Nombre Virus Infection / Hantavirus Pulmonary Syndrome
Hantavirus pulmonary syndrome is a disease characterized by flu-like symptoms that progress rapidly to severe and potentially life-threatening breathing problems.
Recognition of hantavirus pulmonary syndrome began with a mysterious string of illnesses in the southwestern United States in 1993. Several young adults experienced shortness of breath, quickly developed respiratory problems and died shortly thereafter. An investigation identified the cause as one of several hantaviruses.
The hantaviruses that cause the syndrome are carried by several types of rodents, particularly the deer mouse. Humans become infected primarily by breathing air infected with hantaviruses that are shed in rodent urine and droppings.
Although hantavirus pulmonary syndrome has been reported in more than 30 states, it's more common in the 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.
Because treatment options are limited, the best protection against hantavirus pulmonary syndrome is avoidance of rodents and their habitats.
The cause of hantavirus pulmonary syndrome is any number of hantaviruses, each with 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.
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 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 are then easily inhaled.
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.
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. The disease has not been shown to be transmitted from person to person.
Risk factors :
Hantavirus pulmonary syndrome has no race or sex preference. However, certain groups of people — such as hunters or construction workers — are more likely to be exposed to rodents who carry hantaviruses. Thus, the chance of developing the syndrome is greater for people who work, live or play in spaces where rodents live.
Factors and activities that increase the risk of developing hantavirus illness include :
- Opening and cleaning previously unused buildings or sheds
- Housecleaning, particularly in attics or other low-traffic areas
- Having a home or work space infested with rodents
- Having a job that involves exposure to rodents, such as construction, utility work and pest control
- Camping, hiking or hunting
When to seek medical advice :
If you have 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.
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 :
- 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)
- 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 ensue.
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)
Blood tests are the main method for diagnosing hantavirus pulmonary syndrome. These are laboratory tests that analyze blood samples 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 Legionnaires' disease, pneumonic plague and Q fever.
There's no cure for hantavirus pulmonary syndrome, and specific treatment options are limited. However, the prognosis improves with early recognition, immediate hospitalization and adequate respiratory support.
Two hantavirus treatment options currently available 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 airways open and functioning.
- Blood oxygenation. In extremely severe cases of pulmonary distress, a method called extracorporeal membrane oxygenation can help ensure you retain a sufficient supply of oxygen. It 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.
Minimize or eliminate contact with rodents to help prevent exposure to the hantavirus. Although only certain rodent species are known to carry hantavirus, it's best to minimize contact with all rodents, as others may carry pathogens that cause illnesses such as tularemia and hemorrhagic fever.
Take these steps to help prevent hantavirus infection :
- Keep dwellings clean and rodent-free.
- Avoid contact with all rodents — including urban rats — and their droppings.
- Disinfect dead rodents before handling and disposing of them.
- Neutralize rodent droppings or urine with household disinfectants before sweeping or vacuuming.
- Take special precautions, such as wearing a respirator, when cleaning buildings with heavy rodent infestations.