‘Prepare for uncertainty’: Common infections return after COVID-19 disruptions

Providers should “prepare for uncertainty” as common infections such as respiratory syncytial virus and enterovirus return in atypical seasons following disruptions caused by the COVID-19 pandemic, experts said.

Kevin Messacar, MD, PhD, a pediatric infectious disease physician at Children's Hospital Colorado and the University of Colorado School of Medicine and co-author of a new commentary in The Lancet, recalled seeing cases of RSV months out of season, in the spring.

“I remember being down in the laboratory where we report the overnight results, and it started with a trickle of a few RSVs,” Messacar said. “We thought, ‘That's unusual, to be seeing RSV at this time of the year.’ And then it started to be several, and then several dozen, and then many, many detections a day, equivalent to or even surpassing what we would have seen during the winter months. That's when we knew something atypical was happening.”

The usual pattern of influenza and RSV in the winter and enteroviruses in the summer was “thrown off during COVID,” because of the safety precautions being taken to prevent infection during the early pandemic period, Messacar noted.

“We didn't see much activity from those viruses because of the precautions we were taking for COVID,” Messacar said. “Then, as those precautions started to lighten, we started to see those viruses coming back but not in the same way as we had known them to circulate in the past.”

Messacar said they “didn't see RSV come in the winter in 2020, but then it came in the spring, which is really out of season for RSV.”

“We saw the same pattern with influenza, not showing up during the winter, and then persisting into the summer months,” Messacar said. “So, there was a lot of uncertainty as to what is going to happen in the future.”

Messacar reached out to a group of epidemiologic modelers who became three of his co-authors — Rachel E. Baker, PhDBryan Grenfell, PhD and PhD candidate Sang Woo Park of the department of ecology and evolutionary biology at Princeton University — and asked them to predict what would happen in the future.

“Their answer, really, was that we need to prepare for uncertainty ahead,” Messacar said. “All of those patterns that we used to rely on in the past have been thrown off by the fact that we have a year-plus of children who haven't been exposed to those viruses and may not have immunity. Therefore, we might have more susceptible kids out there.”

The group’s modeling suggested the presence of an “immunity gap,” which Messacar explained could lead to more infections happening in a shorter timeframe.

“That could include older children who wouldn’t typically be infected, because those kids didn’t get exposed when they were young,” Messacar said. “Even the smartest epidemiologic modelers are telling us we need to prepare for uncertain times ahead. I think ... that we need to be prepared and watch very closely what's happening with the circulation of these viruses because we can't depend on those former patterns that we used to and prepare for wintertime surges.”

Messacar said clinicians need to be familiar with what is circulating in their own areas.

“A general pediatrician should keep in touch with the local epidemiology of what's circulating and use that to make their clinical practice decisions and decide when they need to test the patient, because I think in basic pediatric practice, a lot of times a test isn't needed,” Messacar said.

“If it's a mild self-limited illness, then the child will recover and doesn't need a test at all, and those are the cases in which oftentimes pediatricians use what is predominantly circulating to make their decisions of, ‘This should run its normal, typical course,’ vs. ‘I need to do further workup,’” he said.

Messacar said the post-pandemic era presents an “unprecedented kind of natural experiment.”

“This hasn't happened since the 1918 influenza pandemic, when they saw the same thing of viruses really going away due to what society did to react to it,” Messacar said. “So we're really in uncharted territory as to what's going to happen moving forward. And I think my overall message would be that we need to prepare for uncertainty.”