Headlines over the past few weeks are ringing the alarm about earlier and more serious influenza (flu) and respiratory syncytial virus (RSV) outbreaks compared with previous years. Add COVID-19 to the mix and you have a dangerous mash of viruses that have many experts calling for caution and searching for explanations.
RSV and the flu “are certainly getting more attention, and they’re getting more attention for two reasons,” said William Schaffner, MD, professor of preventive medicine and infectious diseases at Vanderbilt University, Nashville, Tenn.
“The first is that they’re both extraordinarily early. The second is that they’re both out there spreading very, very rapidly,” he told this news organization.
RSV usually follows a seasonal pattern with cases peaking in January and February. Both viruses tend to hit different regions of the country at different times, and that’s not the case in 2022.
“This is particularly striking for RSV, which usually doesn’t affect the entire country simultaneously,” Dr. Schaffner said.
“Yes, RSV is causing many more hospitalizations and earlier than any previously recorded season in the U.S.,”figures from the Centers for Disease Control and Prevention on RSV hospitalizations, said Kevin Messacar, MD, PhD, associate professor at the University of Colorado at Denver, Aurora, and a pediatric infectious disease specialist at Children’s Hospital Colorado in Aurora.
Although there could be some increase in diagnoses because of increased awareness, the jump in RSV and flu cases “is a real phenomenon for multiple reasons,” said Peter Chin-Hong, MD, professor in the division of infectious diseases at the University of California, San Francisco.
With fewer COVID-related restrictions, people are moving around more. Also, during fall and winter, people tend to gather indoors. Colder temperatures and lower humidity contribute as well, Dr. Chin-Hong said, because “the droplets are just simply lighter.
“I think those are all factors,” he told this news organization.
Paul Auwaerter, MD, agreed that there are likely multiple causes for the unusual timing and severity of RSV and flu this year.
“Change in behaviors is a leading cause,” said the clinical director for the division of infectious diseases at the Johns Hopkins University, Baltimore. More people returning to the workplace and children going to school without masks are examples, he added.
Less exposure to these three viruses also means there was less immune boosting among existing populations, he said. This can lead to “larger susceptible populations, especially infants and younger children, due to the relative absence of circulating virus in past years.”
A leading theory
Are we paying a price now for people following the edicts from officials to mask up, stand apart, and take other personal and public health precautions during the COVID-19 pandemic?
It’s possible, but that may not be the whole story.
“When it comes to RSV, I think that theory of isolation, social distancing, mask wearing, and not attending schools is a very valid one,” Dr. Schaffner said. “That’s everybody’s favorite [reason].”
He said he is confident that the jump in RSV cases is being driven by previous COVID public health protections. However, he’s “a little more cautious about influenza, in part because influenza is so variable.
“Like people in influenza say, if you’ve seen one influenza season, you’ve seen one influenza season,” Dr. Schaffner said.
“There’s a lot of debate,” he added. “Nobody can say definitively whether the immune deficit or debt is a consequence of not being stimulated and restimulated by the influenza virus over the past two seasons.”