Bronchiolitis is a medical condition characterized by inflammatory damage of the bronchioles, the smallest air ways in the lungs. It occurs following a viral infection when there in inflammation of the inner linings of bronchioles resulting in swelling and accumulation of mucus and other respiratory secretions in the lumen of the bronchioles. The most commonly involved virus is the respiratory syncytial virus or RSV and the condition most commonly occurs in the winter season (from later part of fall to early part of spring).
This condition is more common in young children below 2 years of age and the incidence of bronchiolitis reaches its peak among children between 3 and 6 months. Common presenting symptoms include cough, noisy respiration known as wheezing, difficulty in breathing which usually manifest as difficulty in feeding.
Treatment of bronchiolitis includes nebulization of the affected baby with hypertonic saline or sometimes with adrenalin. This condition is quite common about one third of the children develop the symptoms of bronchiolitis during the first year of life.
The condition usually gets better within 3 days however it takes about a week for complete relief of the symptoms. Rarely bronchiolitis may lead to secondary bacterial infection in the lungs, the pneumonia.
Symptoms
Symptoms of bronchiolitis may vary from child to child in severity. In some of the children the presenting symptoms are quite mild in nature however in some they are quite serious. In most of the cases bronchiolitis usually begins as a mild form of upper respiratory tract infection. The symptoms of this upper respiratory tract infection usually deteriorate quite rapidly leading to noisy respiration (wheezing) along with cough.

Common presenting symptoms of bronchiolitis include
1. Bluish discoloration of the skin (cyanosis) due to inadequate oxygen supply
2. Difficulty in respiration as characterized by frequent coughing, noisy respiration (wheezing) and difficulty in feeding
3. Increased tiredness due to interrupted sleep because of cough and shortness of breath
4. Fever
5. Excessive movement of the muscles adjacent to the ribs (accessory muscles of respiration) as there is difficulty in breathing (intercostals retractions)
6. Widening of the nostrils of infants
7. Increased rate of respiration (tachypnea). Sometimes the respiration rate can be as high as 70 per minutes.
Even after relief of the acute attack of bronchiolitis the symptoms especially cough and wheezing can persist for weeks.
Usually the symptoms get better after 7 days however in some cases there is secondary lung infection leading to pneumonia.
In some of the children with history of bronchiolitis there is chance of suffering from asthma in the furure.

Causes
Bronchiolitis mainly affects children below 2 years of age; especially children between 3 and 6 months are at increased risk. The most common viral infection preceding bronchiolitis is respiratory syncytial virus infection (RSV). RSV infection is quite common among children about half of the children have RSV infection at least once by first year of their lives.
However other than RSV other viruses can also lead to bronchiolitis; these are infection influenza, adenovirus, parainfluenza virus, corona virus, rhinovirus, metapneumovirus etc.
These viral infections spread among children through contact with someone (adults or children) suffering from the viral infections. The sources of infection are
1. Respiratory secretions (produced through coughing or sneezing)as present in the adjacent air of an affected person.
2. Coming in close contact (like touching) objects like toys by other affected child.
This condition is more common during the fall and winter season thus this is one of the most common reasons of hospitalization of children during these seasons.

Risk factors
Common risk factors for bronchiolitis include
1. Coming in contact with cigarette smoke
2. Age less than 6 months
3. Living in an overcrowded area where the spread of infection is quite easy
4. Lack of breast feeding
5. Premature birth before completion of 37th weeks of pregnancy

Treatment
The goal of treatment is relieve the symptoms especially shortness of breathing as early as possible. Treatment options include
1. Plenty of fluid intake, either breast milk or formula in children less than 12 months. Electrolyte supplementation is required in older children.
2. Use of humidifier to loosen the mucous plug.
3. Rest
4. Inhalation of epinephrine
5. Oxygen therapy in children with breathing difficulty
Usually antibiotic drugs are not prescribed (only recommended in cases with secondary pneumonia).

Preventive measures
The viral infection preceding bronchiolitis quite easily spreads from infected persons to other non infected children. There are several preventive measures which can reduce the spread of infections; these are
1. Avoiding contact with affected children. The ill child should be separated and needs to stay at home until the symptoms of brponchiolitis relieves.
2. Hand washing helps in prevention of spreading of the disease.
3. Avoiding smoking near a child as it irritates the airways of the child making him or her prone to respiratory tract infections.