A CORK-based professor has spoken of why people who have had Covid-19 do not have quite the same immune system as they once did and in many cases are finding it more difficult to shake respiratory illnesses.

AXA Research Chair of Applied Pathogen Ecology at University College Cork (UCC) Gerry Killeen described Covid-19 as “a lot more severe and complicated” than other respiratory viruses such as the common cold or flu.

“One of the things I find amazing is Covid really gives your immune system a very big hit, it takes out your T cells, your dendritic cells and a lot of those modes of action or very similar to the modes of action that cause Long Covid,” he said.

“I think we’ve all had something over Christmas that we took longer to shake than we normally would.

“This current wave is not just about lack of exposure, it’s also about the fact that none of us have quite the same immune system as we used to have.

“The immune system repertoires that we’re left with are going to have to relearn some tricks. Our immune systems are going to have to learn how to play the game with somewhat fewer cards than they used to have and that’s a big deal.” Mr Killeen said that while it is difficult to know what that looks like in the long term, over years and decades, that the vast majority of variants coming don’t need to be worse, they just need to be different.

“That’s how we can all end up with the cold four to six times a year because there is none of those strains worse than the other, they’re just different.

“So, your immune system reacts to what it saw last and it gets hit. It’s called pathogen diversification where it becomes lots of different things and your immune system can’t be ready for all of them at once.

“Think in cycles of one comes through, we all get immunity against that then that creates space for another one and you can expect it to be very similar to the common cold, to flu, to more extreme things like malaria and dengue but there would be a constant parade of new variants coming through and we shouldn’t be too alarmed about that because that’s quite normal as well for respiratory viruses.

“We’re still in the early stages of the evolution of this thing so there is always the chance that something that is not just different but actually nastier comes through, but I wouldn’t be expecting it tomorrow but it’s something that might hit us at random sometime in the next, five, 10, 20 years,” he said.

Meanwhile, there were 647 Covid-19 cases (PCR) in Cork in the 14 days up to midnight on January 16.

According to the latest data available on the Covid-19 Data Hub which was last updated on January 17, there has been a total of 173,555 Covid-19 cases (PCR) recorded in Cork.

The 14-day incidence rate per 100,000 population up to midnight on January 16 was 119.2.