Children's hospitals in Canada are witnessing an increase in cases of the common respiratory virus that can rarely lead to severe illness in infants, as the respiratory syncytial virus (RSV) causes lung and respiratory infections.

It can cause severe infection in some people, including children under two years old and elderly people with pre-existing conditions. Dr. Earl Rubin, director of the infectious diseases department at Montreal Children's Hospital, says: RSV cases dropped significantly early in the pandemic, but they increased last fall and are now rising in many parts of the country.

Rubin says that the increase in the number of cases is part of the reason his hospital is experiencing long wait times and a shortage of beds.

He said, "We are exhausted; we are seeing in children's hospitals what adult hospitals suffered during the peak of COVID." Rubin says the "triple threat" of influenza, new coronavirus variants, and RSV is worrying.

What are the reasons for the increase in RSV cases? What is RSV?

The virus generally causes cold-like symptoms such as runny nose, cough, and fever. It is the most common cause of lower respiratory tract illness in young children worldwide and usually leads to outbreaks in Canada from late fall to early spring. While many infections are mild colds, children under two are at risk of serious illness such as bronchiolitis — obstruction of the small airways in the lungs — or pneumonia, and may be hospitalized.

Dr. Anna Banerji, an infectious disease specialist and assistant professor at the University of Toronto Faculty of Medicine, said, "Almost all children get infected by age two. It is very common... but some children can get very sick."

In its latest update, the Public Health Agency of Canada reported an increase in RSV cases in many parts of the country, although Banerji says testing is not widespread enough to get a full picture. Hospitals in the United States have also reported increased cases. Quebec’s health department reported a positivity rate higher than the national average.

The CHEO Children's Hospital in Ottawa said in a statement that RSV cases were part of the reason that "September was the busiest month ever."

Why are cases rising now?

Both Banerji and Rubin say there were fewer RSV cases when public health measures were in place due to COVID-19, but there was an increase last fall and again this year as young children were exposed. Banerji said many of these children do not have strong immunity because they had not been exposed before. Similarly, their mothers possibly had not developed immunity to any of these viruses. At his hospital in Montreal, Rubin says he is also seeing some slightly older children between one and two years old who are sicker than usual. He said, "They have no immunity, and if they have any qualifying conditions such as asthma or allergies, that predisposes them [to RSV]."

How does it spread?

Rubin says RSV mainly spreads through droplets and recommends handwashing, and for older children, ensuring they sneeze into their elbow and cover their mouths when coughing. It can also spread through contact.

He said, "If you touch a contaminated surface and then rub your eye or pick your nose, you can infect yourself." People are usually contagious for three to eight days. However, children and people with weakened immune systems can spread RSV for longer periods.

Who is most at risk and what can be done?

People with pre-existing conditions, especially those born prematurely, can be vulnerable to more severe infections. Banerji’s studies also indicate that Inuit children in northern Canada are especially at risk.

She said, "They have much higher admission rates than any other population in the world." During RSV season, antibody-based medication injections are sometimes prescribed to protect premature babies and other children at high risk of severe illness.

Banerji launched a petition — now with over 200,000 signatures — calling on the Nunavut government to expand the use of this medication to make it available to all children in the territory. Generally, doctors may also prescribe oral or inhaled steroids to ease breathing. In severe cases, hospital patients may receive oxygen, a breathing tube, or a ventilator.

Banerji said, "If a child needs to be hospitalized, it is because their oxygen levels are low, or they are struggling to breathe on their own and may require ventilation, or they are not feeding well." She said at home, parents can do their best to manage symptoms with fever-reducing medications and ensure their child stays well hydrated.

Edited by: Yusra Bamatriaf