Back to class… with contagious respiratory infections
August 11, 2025

Every year, September’s back-to-school season not only marks the end of the summer, but also the start of the viral and bacterial infection season [1]. There are several reasons why these infections thrive at this time of year. During the summer holidays, most children have been out in the fresh air and in less confined spaces. Many, however, came into contact with asymptomatic carriers of these microorganisms. As a result, going back indoors, into classrooms, gives children more exposure to those positive cases.
Usually, children can be protected at all times because vaccines are available year-round. If they haven’t had some vaccines yet, September is an ideal opportunity to check their vaccination record and complete the necessary doses, in order to have a safe start to the new school year.
The most common contagious respiratory infections at back-to-school time
Over the course of the school year, children are exposed to a variety of infections, with respiratory infections being the most common. These include colds, flu (influenza), pneumonia, COVID-19 and respiratory syncytial virus (RSV).
More recently, there has been an upsurge in measles (rubeola) and whooping cough (pertussis) in Quebec and elsewhere in Canada, likely a sign of vaccine fatigue or hesitancy [2,3].
In the long term, whooping cough and measles can be prevented through vaccination. On the other hand, infections such as flu and COVID-19 require annual re-vaccination for optimal protection; the viral strains change from year to year.
What about colds? There is no vaccine because they are caused by too many different viruses, making prevention by vaccine practically impossible. As for RSV, school-aged children are not eligible for vaccination [4].
Don’t ignore these warning signs
Even though the symptoms are sometimes dramatic, there are not the same complications with the common cold as there are with measles or whooping cough [5,6]. So, when should you contact a healthcare provider? Santé Québec recommends contacting a healthcare provider or going to the emergency department if a school-aged child has the following signs [7]:
- Rectal temperature ≤ 36°C (sign of hypothermia);
- Fever lasting over 48 hours despite the use of fever medication;
- Paleness or abnormal skin colour;
- Rapid or difficulty breathing despite frequent nasal irrigation with salt water;
- Retracting of the skin under or between the ribs or nasal flaring when breathing;
- Difficulty feeding;
- Moderate to severe signs of dehydration;
- No reaction to stimulation, acting sluggish and less alert;
- Temperature above 38.5°C in a child living with a chronic disease or weakened/deficient immune system.
- Long-lasting coughing spells that make the skin or lips turn red, purple, or blue
- Coughing followed by vomiting
- Whooping sound when your child breathes in after coughing
- Difficulty breathing or brief periods of not breathing (apnea)
- Lethargy (no energy).
- Severe breathing difficulties;
- Persistent, very high fever;
- Mental confusion or altered consciousness;
- Difficulty staying hydrated or dizziness when standing;
- Febrile seizures (fits or convulsions which occur when your child has a high fever);
- Excessive drowsiness, making it hard to wake the child up;
- Wheezing, rapid and irregular breathing or a cough which lasts longer than usual.
How can you identify the cause of a respiratory infection?
There are many different types of respiratory infections, and their symptoms can be similar. In some cases, it’s helpful to identify the specific cause of the infection so you can provide appropriate care.
A number of laboratory techniques are available for this. Some identify microscopic organisms (microorganisms) directly from cultured secretions while others test for microorganism-specific antigens or antibodies produced by the body in response to infection.
The respiratory multiplex PCR test can distinguish over 20 microorganisms from a single sample, including the ones that cause COVID-19, RSV, flu (influenza A and B) and whooping cough.
Other tests are also available for diagnosing streptococcal and tuberculosis infections.
Children with asthma: risks and precautions for heading back to school
Between 10% and 15% of children live with asthma and the back-to-school season is a special challenge for many of them. It is widespread enough that there is a recognized asthma peak at back-to-school time. Respiratory viruses can trigger asthma attacks, but at the same time, children with asthma also have a higher risk of complications when they catch a viral infection.
Going back indoors, to spaces which have often not been ventilated well during the summer, can lead to an increase in mites in the air, a significant factor for asthma attacks. And finally, the stress caused by going back to school can also trigger asthma attacks [10].
Evaluating lung function
The diagnosis of asthma in children is based on a combination of variable respiratory symptoms and objective evidence of expiratory flow limitation. This limitation is generally assessed by pre-post bronchodilator spirometry, which are respiratory function tests. Spirometry, which can be performed from the age of 7, is an essential tool for confirming asthma.
There are two main types of spirometry: simple spirometry and methacholine bronchial challenge spirometry; methacholine is an agent which temporarily narrows the airways (bronchi) in order to assess their sensitivity.
Regular monitoring is important to adjust treatment and monitor changes in respiratory function.
Hygiene and prevention for a healthy return to school
A few preventive measures can help children reduce the risk of catching an infection, while at the same time fully enjoying school and protecting their classmates: * Check your child’s vaccination record and get it updated right away; * Teach your children to wash their hands regularly and properly, and to avoid touching their faces; * Encourage them to cough or sneeze into their elbow to limit the spread of viruses; * Make sure you have good ventilation at home and wipe surfaces down frequently; * Encourage them to stay active outdoors to build their lung capacity; * Keep your home smoke-free; * Follow your healthcare provider’s instructions exactly, especially if your children are living with asthma, have a chronic disease or have an immunodeficiency, since they have a higher risk of respiratory infections.
Conclusion
It’s normal to wonder how to best protect our children from respiratory infections. Fortunately, most of the time, these infections are minor. Following hygiene rules at home and at school can be very helpful.
However, it’s important to contact a healthcare provider quickly if your child has more worrying or persistent symptoms. With prevention and your vigilance, your child can enjoy heading back to school with no worries… and a big grin!
For professional support, we’re here.
Biron provides access to the most common vaccines.
For more information on our services or to make an appointment, contact Biron Groupe Santé customer service at 1 833 251-6006.
Sources10
- Marie-Ève Cousineau. “La ‘rentrée’ des infections”. La Presse, September 5, 2024. La « rentrée » des infections | La Presse. Accessed on August 8, 2025.
- Érika Bisaillon. “Le b.a.-ba de la coqueluche, l’infection respiratoire qui s’abat sur le Canada”. Ici.Radio-Canada, September 2, 2024. https://ici.radio-canada.ca/nouvelle/2101312/augmentation-cas-coqueluche-quebec-canada. Accessed on August 8, 2025.
- Mélanie Meloche-Holubowski. “L’épidémie de rougeole au Canada n’est pas endiguée”. Ici.Radio-Canada, August 2, 2025. https://ici.radio-canada.ca/nouvelle/2183138/epidemie-rougeole-canada-virus-vaccination. Accessed on August 8, 2025.
- Collective. “VRS : vaccin contre le virus respiratoire syncytial”. MSSS. https://www.msss.gouv.qc.ca/professionnels/vaccination/piq-vaccins/vrs-vaccin-contre-virus-respiratoire-syncytial/. Accessed on August 9, 2025.
- Collective. “Infections respiratoires chez l’adulte et chez l’enfant : quoi savoir et quoi faire?” Direction régionale de santé publique de Montréal. https://santepubliquemontreal.ca/conseils-et-prevention/conseils/infections-respiratoires-chez-ladulte-et-chez-lenfant-quoi-savoir-et-quoi-faire. Accessed on August 9, 2025.
- Collective. “Whooping cough”. Santé Québec. https://www.quebec.ca/en/health/health-issues/a-z/whooping-cough. Accessed on August 9, 2025.
- Collective. “Self-care guide for infectious respiratory disease (influenza, COVID-19 or RSV infection)”. Santé Québec. https://www.quebec.ca/en/health/health-issues/flu-cold-and-gastroenteritis/self-care-guide-covid-19. Accessed on August 9, 2025.
- Collective. “(Whooping cough/pertussis) Complications in Children”. Canadian Lung Association. https://www.poumon.ca/complications-chez-l%E2%80%99enfant. Accessed on August 9, 2025.
- Collective. “Coqueluche”. Centre intégré universitaire de santé et de services sociaux de la Mauricie-et-du-Centre du Québec. https://ciusssmcq.ca/conseils-sante/maladies-infectieuses/rougeole/#quand-consulter. Accessed on August 9, 2025.
- Collective. “What do I need to know about asthma triggers?” Government of Canada. https://www.canada.ca/en/public-health/services/chronic-diseases/chronic-respiratory-diseases/what-need-know-about-asthma-triggers.html. Accessed on August 10, 2025.
