The bronchiolitis season has begun. Like influenza epidemics this is an annual event (scourge is a better word) mainly occurring in winter and early spring.

Bronchiolitis is an acute lower respiratory tract viral illness that causes obstruction of the air passages as they enter the lungs. Many different viruses cause bronchiolitis, but respiratory syncytial virus (RSV) is the most common cause. (In fact, bronchiolitis is often referred to as RSV infection.) It is a disease of only young children, with 80 percent of infections occurring in children younger than 1 year of age.

Older children and adults infected with RSV usually get common colds.

Typically, bronchiolitis in a young infant starts as a typical cold. After one to three days, the child begins to breathe more rapidly, often with wheezing. He or she becomes more irritable, less interested in eating and may have a fever.

Although the majority of babies recover uneventfully, 1 percent to 5 percent require hospitalization for labored breathing or for complications such as apnea (breathing stops), pneumonia, and dehydration.

Babies infected before 3 months of age, those with lung and heart disease, and babies born with a gestational age of less than 34 weeks are prone to severe infections.

When children begin to tire from their rapid breathing, when their troubled breathing becomes worse or when they become listless or dehydrated, hospitalization is usually required.

Infants usually start to improve after two to three days.

Children with mild disease are only treated with fluids to prevent dehydration and nasal saline to relieve a stuffy nose.

Because bronchiolitis is a viral infection, antibiotics do not help.

A large study in 2007 found conclusively that corticosteroids such as prednisone are not helpful. Bronchodilators such as albuterol usually are not effective, and current guidelines argue against their routine use.

Ear infection is the most common complication of bronchiolitis, occurring in about 20 percent of patients.

Pneumonia from the virus is relatively common, but a bacterial cause of pneumonia is uncommon.

Even when a child seems to have gotten over the illness, a cough may linger for several weeks. In fact, around 10 percent of children still cough after four weeks.

Call your physician if your child is having difficulty breathing.

Clues that indicate breathing problems include rapid breathing, grunting with breathing, wheezing, flaring of the nostrils with breathing, and a bluish discoloration around the lips and finger tips. Many babies become dehydrated because they work so hard to breathe that they are unable to drink adequate amounts of fluids.

If your child needs to be seen, pulse oximetry to assess oxygenation has become a standard test. A chest X-ray is also often ordered as is a nasal secretion test to detect the presence of RSV.

Blood studies are usually not useful unless other diseases are being ruled out.

Hand washing by family members and other caregivers remains the best bet to prevent spread of the virus, which spreads like a cold.

As with asthma, children with bronchiolitis should avoid exposure to tobacco smoke.

Synagis is a vaccine used to protect high-risk children such as very premature babies and infants with chronic lung disease from getting bronchiolitis. This vaccine is given monthly during the RSV season and is quite expensive.

Although unusual, infants can get bronchiolitis more than once. Be sure to seek medical care if your child is experiencing any difficulty in breathing.

In children younger than 2, it is not always clear cut if the cause is bronchiolitis, asthma, or pneumonia, or any combination.

A broad therapeutic approach may be necessary, but almost always, treatment is successful.

The opinions expressed are solely those of the writer. Robert A. Dershewitz, M.D., Sc.M., FAAP, is a pediatrician at Healthy Kids Care Center in St. John and is affiliated with The Community Hospital in Munster.