Something is altering the normal seasonal currents of cold and flu viruses. They slowed to a trickle during the early part of the COVID-19 pandemic only to blast through human populations this year. Some public health experts have called it a “tripledemic,” but it might even be described as a quadrupledemic.
In the Northern Hemisphere, flu began surging in October, months before its normal season. This year has also seen a steep, early rise in two other viruses, RSV (respiratory syncytial virus) and adenovirus. These normally cause colds, but RSV can be dangerous to young children and has recently led to overcrowding of children’s hospitals. Adenovirus is usually mild too, but this month there were reports of the virus putting college athletes in the ICU, and it’s been implicated in clusters of dangerous hepatitis cases in children.
Why now? The easy answer is that wearing masks for more than two years drove down the incidence of these viruses, and people subsequently lost immunity — something the popular press has dubbed “immunity debt.” But that’s unlikely to be the whole story. The circulation patterns of different viruses appear to be influencing each other in a way that’s not understood, said Michael Osterholm, director of the Center for Infectious Disease Research and Policy and host of a podcast on COVID-19.
