Overview

During the first 2 years of life, children can have different infections that require special attention, one of them is bronchiolitis, a respiratory infection that might need hospitalisation.¹ Although different viruses can cause bronchiolitis, the most common virus causing it is respiratory syncytial virus (RSV).² Therefore, in this article, we will analyse, more in-depth, the role of RSV in bronchiolitis.

What is bronchiolitis?

The respiratory system has airways of different sizes which transport air to the lungs, the smallest airways are named bronchioles. Bronchiolitis occurs when bronchioles are obstructed because there is an inflammation of the tissue inside them and a lot of production of mucus,¹ all of this is caused by an infection.

Different viruses can cause bronchiolitis, for example, respiratory syncytial virus (RSV), influenza viruses, parainfluenza viruses, human bocavirus, human metapneumovirus, adenovirus, and COVID-19.² This disease can happen in adults and children, but it is quite common in children between 0 and 2 years of age.^1,2

What is respiratory syncytial virus (RSV)?

Respiratory Syncytial Virus (RSV) is considered one of the most common causes of respiratory diseases, mainly in children under 5 years of age. However, currently, there has been an increase in cases in people  65 years or older and people with a weakened immune system.³ In addition, it is related to recurring episodes of diseases such as chronic obstructive pulmonary disease and asthma.⁴

RSV can be found and contracted around the world, with more cases presented during autumn and mainly in winter. There are 2 subtypes of the virus RSV-A and RSV-B, which alternate their presence each year.⁴ Both RSV-A and RSV-B can persist for multiple hours on surfaces and objects, and you can contact them by touching these objects or surfaces and then touching your face, eyes, nose or mouth. You can also get them by direct contact with someone infected.

Respiratory syncytial virus (RSV) and bronchiolitis

Bronchiolitis has remained a constant cause of hospitalisation, mainly in children in their first 6 months of life.^1,5 The role of RSV in bronchiolitis is that it is the principal virus found in hospitalised children under 2 years old, causing between 60-80% of the infections.⁵ When patients with bronchiolitis caused by RSV are compared with patients that have bronchiolitis because of other viruses, it has been found that they, usually, have more severe signs and symptoms since their admission to hospital and their recovery is longer.⁶

Risk factors

Some factors make some persons prone to have bronchiolitis caused by RSV,^3,4 some of which are listed below.

Risk factors in babies, toddlers and children

• Babies that were born prematurely
• Low birthweight (less than 2,500 gr)
• Babies of six or fewer weeks of age
• When there is a pre-existent respiratory condition, such as consequences for respiratory distress in newborns
• When there is a previous heart condition, for example, cyanotic congenital heart disease 
• Down syndrome
• People assigned male at birth are at more risk than people assigned female at birth
• Malnutrition
• Children attending daycare or school
• Exposure to tobacco smoke
• Being exposed to high levels of pollution in the air
• Lower socioeconomic status
• Crowded living conditions 

Risk factors in adults

• Previous pulmonary disease, for example, asthma or chronic obstructive pulmonary disease 
• To have a condition which weakens the immune system, such as having a previous organ transplantation
• Being part of the hospital staff 
• Having 65 years or more, in this specific population RSV can produce symptoms similar to Influenza 
• Functional disability 

Symptoms of bronchiolitis

How the disease is presented can vary. However, it has been established that in its beginning, the clinical manifestations are runny nose and sore throat and it looks like a common cold. Then, after between 3 and 5 days the infection gets worse, and it requires more attention to detect warning symptoms that might require prompt medical attention.⁶ The infection usually ends after some days, but in some cases, cough and wheezing can last for some weeks.^{1, 6, 7} After having bronchiolitis for the first time, the infection can occur again, but symptoms tend to be milder. 

Symptoms in babies, toddlers and children

In these pages, the symptoms commonly presented are:⁷

• Cough
• Runny nose
• Difficulty to eat because of pain swallowing
• High temperature (fever) 38℃
• Difficulty breathing or noisy breathing
• Wheezing
• Being irritable, crying a lot and/or feeling tired

Symptoms in adults

The following symptoms can be presented in adults:⁷

• Cough
• Runny nose
• High temperature (fever) 38C
• Sore throat
• Wheezing
• Headache
• General discomfort

Diagnosis 

The diagnosis requires an interrogation about the antecedents and the actual medical condition of the person. Then, performing a physical exploration, the doctor will check the patient’s lungs with a stethoscope, auscultation, and listen for abnormal sounds such as wheezing.^1,2 Additionally, the doctor will check the blood oxygen level in the patient, looking for hypoxaemia, which is a low level of oxygen in the blood.²

To detect the presence of RSV or other virus, it is necessary to collect mucus from the nose of the infected person and send it to the laboratory for testing. A bacterial culture test is sometimes required to discard an over-infection caused by bacteria. If there are abnormal sounds in the lungs during the physical exploration, it might be required to do a chest x-ray.¹ 

Treatment 

There is no specific medication that can be used against RSV. The treatment for bronchiolitis depends on the severity of the symptoms and not on the underlying virus causing it.⁶ Next, we will check some general measures in mild and severe cases.^{1, 2, 6}

Treatment in mild cases

• Increase the quantity of liquids every day to avoid dehydration
• The use of paracetamol or ibuprofen to diminish the episodes of high temperature (fever)
• Using salt water (saline) drops to avoid nose obstruction, in babies and toddlers
• The use of decongestants when they are required in children and adults
• To keep babies and toddlers in a vertical position to help them breathe easily
• To avoid smoke near a person with an infection
• To be aware and look for warning symptoms, during the infection, in case it requires immediate medical attention

Treatment in severe cases

In cases that require hospitalisation, the treatment is more specialised, but in general, these are the measures:

• The rehydration with IV fluids
• The administration of oxygen through different devices to correct hypoxaemia
• Cleaning the airways of any mucus
• It might be required to use antibiotics and/or other medications in case of over-infection

Prevention

These are some measures that can help to avoid bronchiolitis:

• Regular hand washing
• Regular cleaning of surfaces
• Avoid smoking near babies, toddlers, children, or people with previous respiratory conditions
• To avoid contact with people with respiratory diseases
• To stay updated with the vaccination schedule, in the UK, with the NHS vaccination schedule

When to seek medical help?

If the next warning symptoms are presented, it is important to contact medical services, at 999/112 in the UK, or to go to A&E:¹

• Shortness of breath
• Interruptions while breathing
• Constant wheezing
• The sinking of the ribs or the tummy while breathing
• Nasal flaring
• Grunting
• Lips and/or tongue that take a blue hue or tint in colouring.
• Confusion or lack of consciousness

If the next symptoms are presented, it is necessary to look for an urgent appointment with your doctor,² or call 111 in the UK:

• The constant presence of a fever of 38°C
• Worsening of any respiratory symptoms. 
• The presence of symptoms of dehydration

Babies, toddlers and children can additionally present the following symptoms: 

• When they are very sweaty or very hot when touching their body
• When they are very weak or irritable
• When they are eating poorly 

Summary

Although different viruses can cause bronchiolitis, RSV is the principal virus-causing cases that require hospitalisation, mainly in children of 2 years or younger. Creating awareness of this is helpful in preventing the infection, as well as staying alert to warning symptoms that may be presented in an apparent mild infection. Knowing when to ask for medical help is crucial to get adequate treatment.