RSV, Strep A, the flu: a range of familiar bugs are worrying doctors and parents with strange new patterns. What's behind the outbreaks?

As child after child gasping for air was admitted to the hospital, Rabia Agha gritted her teeth. In her role as director of the paediatric infectious diseases division at Maimonides Children's Hospital in New York, she had seen this before. An outbreak of respiratory syncytial virus (RSV) – a winter virus that can feel like a common cold in adults, but which can be dangerous for some young children.

There was a wave last autumn – and an unexpected one in spring this year. Now, in the early autumn months of 2022, it was back again.

"We've had to double the capacity of our ICU," she says, referring to the intensive care unit, reserved for the sickest patients. Some of the children there have been put on mechanical ventilators to help them breathe.

RSV typically hits the youngest children hardest but the patients Agha and her colleagues have treated lately tend to be approaching school age, around three or four years old. In this age group, RSV would usually appear as a cold-like illness, with a runny nose and cough. But now, some of them were struggling.

"Everyone is concerned, obviously, because older children tolerate this virus quite well – why were they not?" she says.

When Covid-19 rampaged across the world, many countries introduced strict lockdowns to thwart transmission of the virus. Children were kept out of schools and nurseries for weeks or months on end. Now that they are mixing again, doctors have noticed periodic surges in other diseases, including RSV, flu and illnesses caused by Group A streptococcus, a bacteria also known as strep A.

Sixteen children have died in the UK since September following strep A infection. According to the UK's Health Security Agency (UKHSA), during 2017-18, the last high season for strep A in the country, a total of 27 deaths in under 18s were recorded. However, the 2022-23 season is not yet over.

Epidemiologists continue to investigate whether Covid-19 lockdowns increased the likelihood of surges in other diseases, given that respiratory infections were more or less stopped in their tracks during the first year or so of the pandemic. There is also the possibility that catching Covid-19 has increased children's susceptibility to other diseases by harming their immune systems somehow – though doctors say this is unlikely, as there is no evidence for such an effect. But what exactly is going on?

For weeks now, on routine conference calls with fellow doctors around the country, Ronny Cheung, a consultant paediatrician in London, has heard reports of strep A infections and respiratory viruses causing problems for children. "It's been notable," he says.

Although strep A, for example, is not usually life-threatening – it might simply cause a sore throat or tonsillitis – in rare cases, it can cause invasive, potentially deadly infections including meningitis.

Cheung stresses that the recent deaths in the UK associated with strep A are extremely unusual: "It doesn't make them any less tragic but it is really important to bear that in mind."

There's a "pretty good argument" behind the idea that infections like this are spiking as a kind of delayed impact of the Covid-19 lockdowns, he suggests. But it is difficult to unpick that from natural seasonal variability.

What the data clearly shows is that, during 2020 and into 2021, the spread of respiratory viruses plummeted, explains Connor Bamford, a virologist at Queen's University, Belfast.

"We saw a real reduction in viruses, mostly RSV and influenza," he says.

The UK Department of Health and Social Care confirmed this trend in March 2021. And figures from Australia and Germany also show a flat-lining of respiratory viruses during the same period.

Researchers then tracked unusual peaks in the months following. A study in Germany found that levels of RSV in the country reached a record high between September and October 2021 – up to 50 times the prevalence recorded in the pre-pandemic years of 2017 to 2019. Medical researchers in New Zealand also noticed a huge spike in RSV cases during 2021.

Nicole Maison at the University Hospital Munich was lead author on the German study. She, like Agha, has seen yet another resurgence of RSV this winter: "We are currently seeing a significant increase in respiratory infections, especially respiratory syncytial virus, in Germany." She adds that she is working on a new paper about the situation.

Besides clinical data, scientists have other ways of monitoring disease transmission. For example, since 2021, Bamford and colleagues have been tracking the prevalence of RSV and flu virus material in wastewater, to better understand transmission of these pathogens in Northern Ireland. Outbreaks are clearly visible in this data, he says.

While our view of what's going on is getting sharper, many unanswered questions remain, including whether Covid-19 infection has actually affected children's immune systems in such a way that they are less able to fight off RSV, strep A, flu and other pathogens.

"We haven't seen any data to support that prior Covid infection decreases your immunity and that you will get a more severe subsequent infection of any other virus or even bacteria," says Agha. She also says she would not, in general, expect to see long-term impacts on children's health or immunity as a result of what is happening now, though those who contract severe lung disease when very young might experience ongoing effects thereof.

Either way, it remains important to protect children as best as possible, she adds. Bamford suggests applying some social distancing, avoiding crowded places and wearing masks in some situations. Improving ventilation indoors could also help.

For strep A, it's possible to use preventative antibiotics in order to reduce the likelihood of infection within a nursery or school where there is a known risk. But one would want this to be targeted, to avoid encouraging antibiotic resistance, says Clare Murray at the University of Manchester.

"Giving it to a whole school is probably over the top," she explains. "Occasionally, we'll give a whole class a prophylaxis if there's been a lot of contact – it's not a new thing."

Both Agha and Cheung expect that the intermittent spikes in childhood diseases that we are seeing post-lockdown will level out. Hopefully things will be back more or less to normal as early as next year, Agha suggests.

Does all of this mean that Covid-19 lockdowns were a bad idea, and put children at risk unnecessarily?

"I absolutely refute that," says Cheung, noting that Covid-19 itself was extremely dangerous and caused large numbers of deaths. Lockdowns, being so disruptive, were likely always going to affect people in negative ways – from the economic impact to effects on mental health and, apparently, disrupting immunity to other viruses.

"This is a cost that we knew we had to bear," adds Cheung. "On balance, it was still the right course of action."

BBC

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