Diseases & Conditions
Respiratory Tract Infections
Respiratory tract infections affect the nose, throat, and airways and may be caused by any of several different viruses.
Children develop on average six viral respiratory tract infections each year. Viral respiratory tract infections include the common cold and influenza (see Viral Infections: Smallpox and Viral Infections: Influenza ). Doctors often refer to these as upper respiratory infections (URIs), because they produce symptoms mainly in the nose and throat. In small children, viruses also commonly cause infections of the lower respiratory tract—the windpipe, airways, and lungs. These infections include croup, bronchiolitis, and pneumonia. Children sometimes have infections involving both the upper and lower respiratory tracts.
In children, rhinoviruses, influenza viruses (during annual winter epidemics), parainfluenza viruses, respiratory syncytial virus (RSV), enteroviruses, and certain strains of adenovirus are the main causes of viral respiratory infections.
Most often, viral respiratory tract infections spread when children's hands come into contact with nasal secretions from an infected person. These secretions contain viruses. When the children touch their mouth, nose, or eyes, the viruses gain entry and produce a new infection. Less often, infections spread when children breathe air containing droplets that were coughed or sneezed out by an infected person. For various reasons, nasal or respiratory secretions from children with viral respiratory tract infections contain more viruses than those from infected adults. This increased output of viruses, along with typically lesser attention to hygiene, makes children more likely to spread their infection to others. The possibility of transmission is further enhanced when many children are gathered together, such as in child care centers and schools. Contrary to what people may think, other factors, such as becoming chilled, wet, or tired, do not cause colds or increase a child's susceptibility to infection.
Symptoms and Complications
When viruses invade cells of the respiratory tract, they trigger inflammation and production of mucus. This situation leads to nasal congestion, a runny nose, scratchy throat, and cough, which may last up to 14 days. Fever, with a temperature as high as 101 to 102° F (about 38.3 to 38.9° C), is common. The child's temperature may even rise to 104° F (40° C). Other typical symptoms in children include decreased appetite, lethargy, and a general feeling of illness (malaise). Headaches and body aches develop, particularly with influenza. Infants and young children are usually not able to communicate their specific symptoms and just appear cranky and uncomfortable.
Because newborns and young infants prefer to breathe through their nose, even moderate nasal congestion can create difficulty breathing. Nasal congestion leads to feeding problems as well, because infants cannot breathe while suckling from the breast or bottle. Because infants are unable to spit out mucus that they cough up, they often gag and choke.
The small airways of young children can be significantly narrowed by inflammation and mucus, making breathing difficult. Children breathe rapidly and may develop a high-pitched noise heard on breathing out (wheezing) or a similar noise heard on breathing in (stridor). Severe airway narrowing may cause children to gasp for breath and turn blue (cyanosis). Such airway problems are most common with infection caused by parainfluenza viruses and RSV. Affected children need to be seen urgently by a doctor.
Some children with a viral respiratory tract infection also develop an infection of the middle ear (otitis media) or the lung tissue (pneumonia). Otitis media and pneumonia may be caused by the virus itself or by a bacterial infection that develops because the inflammation caused by the virus makes tissue more susceptible to invasion by other germs. In children with asthma, respiratory tract infections often lead to an asthma attack.
Doctors and parents recognize respiratory tract infections by their typical symptoms. Generally, otherwise healthy children with mild upper respiratory tract symptoms do not need to see a doctor unless they have trouble breathing, are not drinking, or have a fever for more than a day or two. X-rays of the neck and chest may be taken in children who have difficulty breathing, stridor, wheezing, or audible lung congestion. Blood tests and tests of respiratory secretions are rarely helpful.
Pneumonia in an Infant
Prevention and Treatment
The best preventive measure is practicing good hygiene. A sick child and the people in the household should wash their hands frequently. In general, the more intimate physical contact (such as hugging, snuggling, or bed sharing) that takes place with an ill child, the greater the risk of spreading the infection to other family members. Parents must balance this risk with the need to comfort an ill child. Children should stay home from school or child care until the fever is gone and they feel well enough to attend.
Influenza is the only viral respiratory infection preventable by vaccination. All children aged 6 to 59 months should receive a yearly vaccination, as should older children with certain disorders. Such disorders include heart or lung disease (including cystic fibrosis and asthma), diabetes, kidney failure, and sickle cell disease. Additionally, children whose immune system is compromised (including children with human immunodeficiency virus [HIV] infection and those undergoing chemotherapy) should receive the vaccine.
Antibiotics are not necessary to treat viral respiratory tract infections. Children with respiratory tract infections need additional rest and should maintain normal fluid intake. Acetaminophen Some Trade Names TYLENOL or nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen Some Trade Names ADVIL MOTRIN NUPRIN , can be given for fever and aches. School-aged children may take a non-prescription decongestant for bothersome nasal congestion, although the drug often does not help. Infants and younger children are particularly sensitive to the side effects of decongestants and may experience agitation, confusion, hallucinations, lethargy, and rapid heart rate. In infants and young children, congestion may be relieved somewhat by using a cool-mist vaporizer to humidify the air and by suctioning the mucus from the nose with a rubber suction bulb.
Respiratory Syncytial Virus
Respiratory syncytial virus causes upper and lower respiratory tract infections.
Respiratory syncytial virus (RSV) is a very common cause of respiratory tract infection, particularly in children. Nearly all children have been infected by age 4 years, many in the first year of life. Infection does not provide complete immunity, so reinfection is common, although usually less serious. Outbreaks typically occur in winter and early spring.
The first infection often involves the lower respiratory tract, most commonly producing bronchiolitis (see Respiratory Disorders: Bronchiolitis ). Later infections usually involve only the upper respiratory tract. Children who have had bronchiolitis have an increased risk of developing asthma when they are older. Children with serious underlying disorders (such as congenital heart disease, asthma, cystic fibrosis, or immune system suppression) or who were born prematurely are at particular risk of developing serious illness. Adults are also infected with RSV, and the elderly may develop pneumonia.
Symptoms and Diagnosis
A runny nose and fever begin 3 to 5 days after infection. About half of children with a first infection also develop a cough and wheezing, indicating lower respiratory tract involvement. In infants less than 6 months old, the first symptom may be a period of not breathing (apnea). Some children, usually young infants, develop severe respiratory distress, and a few die.
Doctors usually recognize RSV infection when the typical symptoms occur at the expected time of year or during an outbreak. Tests are usually not performed unless doctors are trying to identify an outbreak. When necessary, samples of nasal secretions are sent for a rapid antigen test.
Prevention and Treatment
Doctors may give monthly injections of palivizumab Some Trade Names SYNAGIS , which contains antibodies against RSV, to children who are at high risk of developing a severe RSV infection. Children who receive palivizumab Some Trade Names SYNAGIS are less likely to need hospitalization, but doctors are not sure whether this treatment prevents death or serious complications.
Children who have difficulty breathing are taken to a hospital. Depending on their condition, doctors may treat them with oxygen and drugs, such as albuterol Some Trade Names PROVENTIL VENTOLIN or epinephrine Some Trade Names ADRENALIN , to open the airways (bronchodilators). Ribavirin Some Trade Names VIRAZOLE , an antiviral drug, is no longer recommended except for children whose immune system is severely compromised.
Last full review/revision May 2007 by Mary T. Caserta, MD
Source: The Merck Manual Home Edition