Respiratory Syncytial Virus Infection

Respiratory syncytial virus infection

Definition

Respiratory syncytial virus (RSV) is a virus that can cause severe lower respiratory infections in children younger than two years of age and milder upper respiratory infections in older children and adults. RSV infection in young children is also called bronchiolitis , because it is marked by inflammation of the bronchioles, the narrow airways that lead from the large airways (bronchi) to the tiny air sacs (alveoli) in the lungs. The symptoms include wheezing, difficulty breathing, and sometimes respiratory failure.

Description

RSV infection is caused by a group of viruses found worldwide. There are two different subtypes of the virus with numerous different strains. Taken together, these viruses account for a significant number of deaths in infants.

RSV infection shows distinctly different symptoms, depending on the age of the infected person. In young children, the virus causes a serious lower respiratory infection in the lungs. In older children and healthy adults, it causes a mild upper respiratory infection often mistaken for the common cold .

Although anyone can get this disease, infants suffer the most serious symptoms and complications. Breast-feeding seems to provide partial protection from the virus. Conditions in infants that increase their risk of infection include:

• premature birth
• lower socio-economic environment
• congenital heart disease
• chronic lung diseases, such as cystic fibrosis
• immune system deficiencies, including HIV infection
• immunosuppressive therapy, such as that given to organ transplant or cancer patients

Many older children and adults get RSV infection, but the symptoms are so similar to the common cold that the true cause is undiagnosed. People of any age with compromised immune systems, either from such diseases as AIDS or leukemia, or as the result of chemotherapy or corticosteroid medications, and patients with chronic lung disease are more at risk for serious RSV infections.

Demographics

RSV infection is primarily a disease of winter or early spring, with waves of illness sweeping through a community. The rate of RSV infection is estimated to be 11.4 cases for every 100 children during their first year of life. In the United States, RSV infection occurs most frequently in infants between the ages of two months and six months.

Respiratory syncytial virus is spread through close contact with an infected person. It has been shown that if a person with RSV infection sneezes, the virus can be carried to others within a radius of 6 feet (1.8 m). This group of viruses can live on the hands for up to half an hour and on toys or other inanimate objects for several hours.

Scientists had, as of 2004, not understood why RSV viruses attack the lower respiratory system in infants and the upper respiratory system in adults. In infants, RSV begins with such cold symptoms as a low fever , runny nose, and sore throat . Soon, other symptoms appear that suggest an infection that involves the lower airways. Some of these symptoms resemble those of asthma . RSV infection is suggested by the following characteristics:

• wheezing and high-pitched, whistling breathing
• rapid breathing (more than 40 breaths per minute)
• shortness of breath
• labored breathing out (exhalations)
• bluish tinge to the skin (cyanosis)
• croupy, seal-like, barking cough
• high fever

Breathing problems occur in RSV infections because the bronchioles swell, making it difficult for air to get in and out of the lungs. If the child is having trouble breathing, immediate medical care is needed. Breathing problems are most common in infants under one year of age; they can develop rapidly.

Diagnosis

Physical examination and imaging studies

RSV infection is usually diagnosed during a physical examination by the pediatrician or primary care doctor. The doctor listens with a stethoscope for wheezing and other abnormal lung sounds in the patient's chest. The doctor will also take into consideration whether there is a known outbreak of RSV infection in the area. Chest x rays give some indication of whether the lungs are hyperinflated from an effort to move air in and out. X rays may also show the presence of a secondary bacterial infection, such as pneumonia .

Laboratory tests

A nasal swab can be obtained to isolate the virus or antibodies to the virus in secretions. If infants are hospitalized, other tests such as an arterial blood gas analysis are done to determine if the child is receiving enough oxygen.

Treatment

Home care

Home treatment for RSV infection is primarily supportive. It involves taking steps to ease the child's breathing. Dehydration can be a problem, so children should be encouraged to drink plenty of fluids. Antibiotics have no effect on viral illnesses. In time, the body will make antibodies to fight the infection and return itself to health.

Home care for keeping a child with RSV comfortable and breathing more easily includes:

• use of a cool mist room humidifier to ease congestion and sore throat
• elevation of that baby's head by putting books under the head end of the crib
• acetaminophen (Tylenol, Pandol, Tempra) for fever (Aspirin should not be given to children because of its association with Reye's syndrome , a serious disease.)
• For babies too young to blow their noses, suctioning mucus with an infant nasal aspirator

Hospital treatment

In the United States, RSV infections are responsible for 90,000 hospitalizations and 4,500 deaths each year. Children who are hospitalized receive oxygen and humidity through a mist tent or vaporizer. They also are given intravenous fluids to prevent dehydration. Mechanical ventilation may be necessary. Blood gases are monitored to assure that the child is receiving enough oxygen.

Medications

Bronchiodilators, such as albuterol (Proventil, Ventilin), may be used to keep the airways open. Ribavirin (Virazole) is used for desperately ill children to stop the growth of the virus. Ribavirin is both expensive and has toxic side effects, so its use is restricted to the most severe cases.

Prognosis

RSV infection usually runs its course in seven to 14 days. The cough may linger for weeks. There are no medications that can speed the body's production of antibodies against the virus. Opportunistic bacterial infections that take advantage of a weakened respiratory system may cause ear, sinus, and throat infections or pneumonia.

Hospitalization and death are much more likely to occur in children whose immune systems are weakened or who have underlying diseases of the lungs and heart. People do not gain permanent immunity to respiratory syncytial virus and can be infected many times. Children who suffer repeated infections seem to be more likely to develop asthma in later life.

KEY TERMS

Alveoli —The tiny air sacs clustered at the ends of the bronchioles in the lungs in which oxygen-carbon dioxide exchange takes place.

Antibody —A special protein made by the body's immune system as a defense against foreign material (bacteria, viruses, etc.) that enters the body. It is uniquely designed to attack and neutralize the specific antigen that triggered the immune response.

Reye's syndrome —A serious, life-threatening illness in children, usually developing after a bout of flu or chickenpox, and often associated with the use of aspirin. Symptoms include uncontrollable vomiting, often with lethargy, memory loss, disorientation, or delirium. Swelling of the brain may cause seizures, coma, and in severe cases, death.

Prevention

As of 2004, there were no vaccines against RSV. Respiratory syncytial virus infection is so common that prevention is impossible. However, steps can be taken to reduce a child's contact with the disease. People with RSV symptoms should stay at least six feet away from young children. Frequent hand washing, especially after contact with respiratory secretions, and the correct disposal of used tissues help keep the disease from spreading. Parents should try to keep their children under 18 month of age away from crowded environments where they are likely to come in contact with older people who have only mild symptoms of the disease. Childcare centers should regularly disinfect surfaces that children touch.

Parental concerns

Because symptoms of severe respiratory distress may be subtle in very young babies, parents need to keep a high level of suspicion when young babies contract a respiratory illness, particularly young babies with a history of prematurity or other risk factor for severe RSV infection.

Resources

BOOKS

McIntosh, Kenneth. "Respiratory Syncytial Virus." In Nelson Textbook of Pediatrics. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2004.

Tristram, Debra A., and Robert C. Welliver. "Respiratory Syncytial Virus." In Principles and Practice of Pediatric Infectious Diseases, 2nd ed. Edited by Sarah S. Long et al. St. Louis, MO: Elsevier, 2003.

Tish Davidson, A.M. Rosalyn Carson-DeWitt, MD