Covid continues to cause more disruption to the NHS than all other infectious diseases combined.

The trouble with "living with" a virus that evolves as rapidly as this one is that we will be faced with successive waves as it continually develops new mutations which enable it to become more transmissible and more immune evasive.

Unlike influenza, which tends to have one annual peak, Covid shows no sign of disappearing.

The Herald: Flu tends to occur in single annual peaks. Case numbers in December 2022 were abnormally high after two very subdued winters as a result of Covid-related restrictionsFlu tends to occur in single annual peaks. Case numbers in December 2022 were abnormally high after two very subdued winters as a result of Covid-related restrictions (Image: PHS)

"We had a relatively large wave in March, we're seeing case rises again," said Dr Toni Ho, of Glasgow's Centre for Virus Research.

"It's evolving quickly. The dominant variant changes every three to four months, the population builds up immunity to that variant, and so immune pressure drives a different variant to emerge.

"That cycle will carry on."

READ MORE: Hundreds of hospital wards closed due to Covid outbreaks 

Attention has turned to EG5.1 - nicknamed Eris - which is already dominant in Asia and responsible for an estimated one in seven cases in the UK.

Another offshoot of the Omicron lineage, it appears to be yet more resistant to Covid antibodies but there is no evidence that it is more virulent.

Slightly more worrying has been the emergence of BA2.86, which has triggered alarm bells because it has an estimated 33 new mutations on its spike protein.

The last time we saw this many changes in a single evolutionary leap was with Omicron at the end of 2021.

READ MORE: Covid reinfections and the rise of Omicron

That proved to be a game-changer, ushering in an era of repeat infections and super-transmissible strains which made social distancing and standard facemasks much less effective.

Cases of BA2.86 - dubbed Pirola - have been detected in several countries including the UK.

Overall Covid incidence, based on people testing positive in hospital, has increased nearly five-fold in Scotland since the beginning of July, though there is nothing to suggest people are becoming sicker.

The Herald: The number of people in hospital with Covid has climbed from 66 on July 1 to 315 on August 18 (Image: PHS/NB: definition of Covid inpatients altered from May 8th to include only patients who had tested positive in prior 10 days, not 28)The number of people in hospital with Covid has climbed from 66 on July 1 to 315 on August 18 (Image: PHS/NB: definition of Covid inpatients altered from May 8th to include only patients who had tested positive in prior 10 days, not 28) (Image: PHS)

Whether BA2.86 peters out like its predecessors or marks a new watershed - maybe even a new Greek letter from the World Health Organisation (Pi is next) - remains to be seen.

But we are heading for our fourth winter of Covid with fewer precautions than ever and a scaled back booster programme with vaccines offered to over-65s this year instead of all over-50s.

READ MORE: NHS buckles under 'extraordinary' early flu wave 

Meanwhile, in a signal for what may lie ahead, Australia is emerging from another tough flu season - one which appears to have disproportionately sickened children. 

The NHS is very far from recovered; the last thing it needs is another "twindemic" of Covid and flu.