Before Covid, few people had heard of respiratory syncytial virus (RSV). Increasingly, though, this common cause of pneumonia and bronchiolitis (airway inflammation) is filling up hospital beds across Europe and the Americas. Combined with rising admissions for other respiratory infections, including influenza and Covid, it is pushing some healthcare systems close to the brink of collapse.
In its latest report, the European Centre for Disease Prevention and Control (ECDC) said a number of countries had been experiencing unusually early increases in RSV detections, with rising paediatric hospital admissions in France, Ireland, Spain, Sweden and the US.
“With the continued impact of the Covid-19 pandemic and the circulation and health impact of other respiratory pathogens, it is challenging to predict how the new winter period will develop,” a joint statement by the ECDC, European Commission and World Health Organization said.
The Pan American Health Organization (PAHO) issued a similar statement last month, as the virus burdens healthcare systems across Canada, Mexico, Brazil, Uruguay, and the US, with children and infants under the age of one particularly affected. “The rise of a single respiratory infection is a cause for concern. When two or three start impacting a population concurrently, this should put us all on alert,” said the PAHO director, Dr Carissa F Etienne.
A “tripledemic” of Covid, RSV and flu is bad news for adult hospital wards: even in a normal year, an estimated 60,000 to 120,000 older adults are hospitalised and 6,000 to 10,000 of them die from RSV in the US alone.
However, the bigger threat is to children’s health. RSV is a common respiratory virus that usually causes mild cold-like symptoms but it is a leading cause of of pneumonia and bronchiolitis in young infants. Worldwide, it is responsible for about 3.6 million hospital admissions and more than 100,000 deaths in under-fives each year.
Even in wealthy countries, one in 56 babies who are born on time and are otherwise healthy will be hospitalised with RSV during their first year of life. There are no drugs but those with severe infections may be supported with supplemental oxygen, intravenous fluids, or mechanical ventilation until they get better. Having sufficient intensive care beds is therefore essential.
Before the arrival of Covid, RSV followed a predictable pattern, with low rates during summer and a sharp increase in infections in winter. Paediatric wards would be stretched but because they could plan for these annual peaks they were rarely overwhelmed.
However, since Covid restrictions were lifted, that ability to plan has largely evaporated. For instance, between July 2021 and February 2022, the US experienced consistently high RSV infections, followed by a further spike during July and August 2022. Now, they are soaring again, with RSV hospitalisation rates for newborns seven times higher than they were in 2018, the last full season before the pandemic.
In European countries, the usual pattern has been disrupted. “In previous years, we had a system where if there was not enough capacity in the Netherlands, children would go to Germany or Belgium because those countries had already had their RSV season, or it was still to come,” said Prof Louis Bont, a paediatric infectious diseases specialist at the Wilhelmina children’s hospital in Utrecht, the Netherlands.
“Now, at the moment we are reaching our peak, Germany is also transferring children to the Netherlands. It seems that several neighbouring countries may have reached the peak of their epidemics at the same time.”
Combined with influenza, and human metapneumovirus infections – another common respiratory virus that can cause breathing difficulties in young children – the coming weeks and months could be difficult.
“Usually, these viruses follow each other, so first you have one virus, then the other, then the other, but now they all seem to be coming at the same time,” Bont said.
“RSV is the most problematic but the pressure on paediatric wards, and in particular intensive care units, is really making it difficult to have enough capacity to take care of life-threateningly ill children.”
Sebastian Brenner, the head of the paediatric intensive care unit at University hospital, Dresden, told the German news channel n-tv: “If the forecasts are right, then things will get significantly more acute in the coming days and week.
“We see this in France, for example, and in Switzerland. If that happens, then there will be bottlenecks when it comes to treatment.”
Precisely why RSV is behaving in this way is unclear but a leading theory is that protective measures introduced during the pandemic, such as lockdowns and social distancing, interrupted RSV transmission, resulting in a cohort of young children who had never been exposed to it and developed any immunity. Now those restrictions have been lifted, there is a bigger pool of susceptible individuals.
Whether the rise in European countries and the US will translate into a significant increase in child deaths is also uncertain. However, in countries with less developed healthcare systems, unpredictable spikes in RSV could be deadlier.
Steve Cunningham, a professor of paediatric respiratory medicine at the University of Edinburgh, said “In areas of east Africa, where there is a lot of famine concern at the moment, it wouldn’t take much to cause a major outbreak of RSV. We’re seeing it out of season, so they may well see it out of season.”
Yet, survival is not the only consideration. “Even when kids survive a bout with RSV, they can experience lasting effects,” said Keith Klugman, the director of pneumonia at the Bill and Melinda Gates Foundation.
For instance, studies have suggested that infants who are hospitalised with severe RSV may be more susceptible to pneumonia or asthma in later life, although these links are still being investigated.
Having a baby admitted to intensive care can also take a psychological toll. “Parents have said that, even a year afterwards, their family is not the same as it was before,” Bont said.
The good news is that the current unusual situation is unlikely to continue for ever. “Unless something new happens, probably within 12 months we will go back to normal,” Bont said.
There is also a raft of drugs and vaccines against RSV in late-stage clinical trials, including an antibody-based drug called nirsevimab, which was recently approved by the European Commission, and which is designed to protect babies during their first RSV season, when they are most vulnerable. A trial to establish the cost-effectiveness of the drug is recruiting babies across the UK, France and Germany.
Pfizer also recently announced top-line results from a phase 3 trial of its RSV vaccine candidate, which is designed to be given to pregnant women, suggesting an efficacy of 69% against hospitalisation with RSV during a baby’s first six months of life.
Even once RSV returns to its normal seasonal pattern, it remains the second largest killer of infants, behind malaria. So, if these drugs and vaccines are approved and funded, it would be a significant achievement. Until then, prevention remains the best strategy, which means practising good hygiene and limiting contact with other people, if you suspect you or your child is infected.
Cunningham also emphasised the need for vigilance. “If parents, in particular, are aware of RSV, then that’s great, because if what seems like a pretty bad cold gets a lot worse and their child’s feeding is affected, and their breathing becomes more laboured, then they need to seek medical review.”