In particular RSV, respiratory syncytial virus: "RSV is a common respiratory illness. In adults, it generally only produces very mild symptoms – but it can make young children extremely ill, or even be fatal.
https://www.theguardian.com/world/2021/ ... unity-debtNew Zealand has reported nearly 1,000 RSV cases in the past five weeks, according to the Institute of Environmental Science and Research. The usual average is 1,743 over the full 29-week winter season. Australia is also experiencing a surge, with overcrowded Victoria hospitals also hit by unusually high rates of RSV...
Epidemiologist and public health professor Michael Baker used the metaphor of forest brushfires: if a year or two have passed without fire, there is more fuel on the ground to feed the flames. When a fire finally comes, it burns much more fiercely. “What we’re seeing now is we’ve accumulated a whole lot of susceptible children that have missed out on exposure – so now they’re seeing it for the first time,” Baker said.
The “immunity debt” phenomenon occurs because measures like lockdowns, hand-washing, social distancing and masks are not only effective at controlling Covid-19. They also suppress the spread of other illnesses that transmit in a similar way, including the flu, common cold, and lesser-known respiratory illnesses like RSA. In New Zealand, lockdowns last winter led to a 99.9% reduction in flu cases and a 98% reduction in RSV - and near-eliminated the spike of excess deaths New Zealand usually experiences during winter...
Usually, people experience near-universal exposure to RSV as children, Baker said, with most exposed in their first year of life...