Three years into the pandemic, COVID-19 is still going strong, causing wave after wave as case numbers rise, ebb, and then rise again. But last fall there was something new — or rather, something old: the return of the flu. Also, respiratory syncytial virus (RSV) — a virus that makes few headlines in normal years — ignited in its own wave, causing a “triple disease.”
The increases in these old enemies were particularly noticeable because influenza and RSV had all but disappeared during the first two winters of the year Pandemic. A specific version of the flu can be even more surprising are extinct during the early COVID pandemic. those of the World Health Organization monitoring program has not conclusively detected the B/Yamagata flu strain since March 2020. “I don’t think anyone is going to stick their neck out and say it’s gone yet,” says Richard Webby, a virologist at St. Jude Children’s Research Hospital in Memphis. But, he adds, “we hope it was squeezed out.” Such an extinction would be a super rare event, Webby says.
But then again, the past few years have been very unusual times for human-virus relationships, and lockdowns and masks have gone a long way in preventing influenza and RSV from entering the human nose. Still, Webby thinks another factor may have kept her in check while COVID raged. It’s called viral interference and simply means that the presence of one virus can block another.
Viral interference can occur in single cells in the lab and in individual animals and people exposed to multiple viruses — but it can also affect entire populations if enough people get virus for it to prevent others from thriving at scale. The result is waves of infection from individual viruses that alternately dominate. “Looking back over the past few years, I’m pretty confident in saying that COVID can certainly block flu and RSV,” says Webby.
It wouldn’t be the first time scientists have observed such patterns. In 2009, for example, the virus to fear was swine flu, which jumped from pigs to humans earlier that year. Things looked set to pick up again in autumn – but suddenly things stagnated in some parts of Europe. The rhinovirus, which is responsible for the common cold and is likely transmitted by children returning to school, took center stage for a number of weeks before swine flu regained the upper hand. Then this flu strain delayed the typical fall promotion of the RSV by up to two and a half months.
There are a number of ways that disorders can occur in the body. One occurs when two viruses use the same molecule to enter host cells. If Virus A gets there first and latches on to all those molecular doorknobs, then Virus B is out of luck.
Another type of interference can occur when two viruses compete for the same resources within the cell, e.g. B. the machinery to make new viral proteins or the ability to escape that cell to infect others. “Think of it as a race between two viruses,” says Webby.
But the best-understood method of interference involves a defense molecule called interferon made from cells of all animals with backbones (and possibly some invertebrates as well). In fact, viral interference is the Reason interferon got its name first. When a cell senses a virus, any virus, it starts making interferon. And that in turn activates a lots of defense genes. Some of the products of these genes act inside the cell or at its borders, preventing further viruses from entering and pre-existing viruses from replicating or leaving the cell.
Cells secrete interferon into their environment, warning other cells to increase their alertness. The consequence of this: If a second virus then appears, the cells have already activated their defense and may be able to fight it off.
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