Runny Nose and Productive Coughing
(Merck Manual)

Respiratory tract infections affect the nose, throat, and airways and may be caused by any of several different viruses.

Viral respiratory tract infections include the common cold and the flu. Doctors often refer to these as upper respiratory infections (URIs), because they produce symptoms mainly in the nose and throat. In infants and small children, viruses also commonly cause infections of the lower respiratory tract—the trachea, bronchi and lungs. These infections include laryngitis, bronchitis, bronchiolitis, and pneumonia. Children sometimes have infections involving both the upper and lower respiratory tracts.

Most often, viral respiratory tract infections spread when children's hands come into contact with nasal secretions from an infected person or when children breathe air containing droplets that were coughed or sneezed out by an infected person. Children are more likely to spread their infection to others than adults. 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 leads to nasal congestion, a runny nose, 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).

The most common complications of a viral, upper respiratory tract infection are a bacterial infection of the middle ear (otitis media) or the lung tissue (pneumonia). This develops because the inflammation caused by the virus makes tissue more susceptible to invasion by bacteria. In children with asthma, respiratory tract infections often lead to an asthma attack.

Diagnosis
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 few days. X-rays of the lungs and blood tests are used to rule out bacterial complications.