Responding to a member of the public on social media, Prof Sridhar, chair of global public health at Edinburgh University, said a mass event such as COP26 “will cause an increase in cases”.
In the case of Covid, she added, this would put further stress on limited health services, “which triggers [the] need for further restrictions”.
But her comments have sparked a backlash from leading business groups, with the Scottish Hospitality Group warning against “scaremongering” in the run-up to Christmas amid claims that any re-tightening of restrictions over winter could cost tens of thousands of jobs.
It comes as the daily number of Covid cases reported in the UK surpassed 50,000 for the first time since mid-July.
Scotland recorded 32 coronavirus deaths and 2,355 cases in the 24 hours to Thursday. There were 917 people in hospital on Wednesday with recently confirmed Covid-19, up 27 on the previous day, with 58 in intensive care, up seven.
Boris Johnson continued to resist calls from health leaders for tighter Covid restrictions over winter despite the rising levels of infections.
The Prime Minister acknowledged the numbers were “high”, but said they were “within the parameters” forecast by scientists advising the UK Government.
UK health secretary Sajid Javid had earlier said on Wednesday this “Plan B” of restrictions, which include many already in place in Scotland, such as mandatory face coverings, remote working and vaccine passports, would not yet be implemented.
But Prof Sridhar later posted on Twitter: “Expect Plan B in the next week or two.”
She added: “And not underplaying at all the significance of climate change, but I’m concerned about impact of #COP26 in Glasgow on COVID control as we head into winter. Probably worst timing ever in a pandemic.”
Asked by a member of the public if the conference would make the Covid situation in Scotland worse, and increase the risk of further restrictions, Prof Sridhar said: “I could be wrong (and hope I am) but yes.
"A mass event (with major movement of people in & out) with an infectious virus will cause an increase in cases. While in the case of COVID will put stress on limited health services. Which triggers need for further restrictions.”
The NHS in Scotland is “on a knife edge” in some areas, the British Medical Association (BMA) has warned.
Four health boards have so far requested help from the Army to cope with high demand and staffing shortages.
Some 86 personnel began work with NHS Lanarkshire and NHS Borders this week, with requests from NHS Grampian and NHS Ayrshire and Arran still under consideration.
More than 100 personnel are already working to support the ambulance service.
Responding to Prof Sridhar's comments, the Scottish Chambers of Commerce warned any further restrictions this winter would be a “painful setback” to businesses, and put tens of thousands of jobs at risk.
Chief executive Dr Liz Cameron said: “Scottish businesses would see a return to tighter Covid-19 restrictions this winter as a painful setback to business confidence and the progress that they have made towards economic recovery.
“It would also place tens of thousands of jobs at risk, especially as businesses can no longer access the furlough scheme, which played a vital role in protecting jobs in Scotland when it was live.”
She added: “This would be on top of many other rising concerns to Scottish businesses; inflation, taxation and surging costs such as energy prices. Placing businesses under tighter restrictions would have a devastating impact and derail prospects of a recovery for many.
“The Scottish Government’s top priority should be to allow the economy to safely operate and instead focus on maximising our testing and vaccination programme.”
The Scottish Hospitality Group said any further restrictions would have an “absolute detrimental effect”.
Stephen Montgomery, spokesperson for the group, also warned against “scaremongering” in the run-up to Christmas.
“We already had Christmas cancelled last year and we don’t want it cancelled this year,” he said.
“That was the idea of having Covid certification coming into pubs, that we would remain open.”
He added: “We're all depending on Christmas this year.
“Even now people are dubious about Christmas because of the Covid certification, especially coming to Hogmanay … so any restriction now, at all, in any way, that comes into hospitality is going to have an absolute detrimental effect to everybody.
“Not just hospitality – [the] supply chain, who are already struggling, producers who are already struggling ... everybody.”
Scottish Labour said the calls from Prof Sridhar highlighted the need for a faster rollout of booster Covid jags.
The party’s health spokesperson Jackie Baillie said: “Whilst not entirely surprising, it is nevertheless troubling to hear Prof Sridhar warn of a potential spike in cases as a result of COP26 taking place in Glasgow.
“Covid cases are already far too high and lives are being lost.
“If we are to prevent cases spiking, and the inevitable additional pressure that would put on our NHS, we need the SNP Government to speed up the sluggish roll-out of the booster jab and ensure the NHS has surge capacity.
“It is not good enough to wait for cases to spike before taking action. The health secretary must act and act now.”
Scottish Liberal Democrats leader Alex Cole-Hamilton also urged the government to act now to support the NHS.
"We saw from the G7 in Cornwall that these major gatherings can bring with them a spike in Covid cases,” he said.
“The Scottish Government should set out what proactive measures it is putting in place to enable NHS Greater Glasgow and Clyde and others to deal with any rise in cases associated with COP26.
"With experts like Prof Sridhar already warning of the risk, there is no excuse for the health secretary to be taken by surprise. He should move to support our NHS now."
A spokesperson said the Scottish Government had “no current plans to introduce further restrictions”.
“Covid-19 continues to be closely monitored by all relevant agencies and we are working with the UK Government, Public Health Scotland and our partners in Glasgow to plan for the event and ensure appropriate mitigation measures are in place,” the spokesperson said.
COP26 delegates will be exempt from the vaccine passport scheme, but the Scottish Government spokesperson said that participants would be asked to respect one metre distancing and wear face coverings.
Both the NHS Confederation and the BMA have separately urged ministers to activate their winter Plan B for England amid fears the health service could be overwhelmed.
BMA council chair Dr Chaand Nagpaul said the refusal to introduce supplementary measures amounted to “wilful negligence”.
However, Mr Johnson said the successful rollout of the vaccination programme meant the country was in an “incomparably better” position than it was 12 months ago and stressed the UK Government was sticking with its Plan A.
“We are continuing with the plan we set out in July,” he said. "We are watching the numbers very carefully every day.
“The numbers of infections are high, but we are within the parameters of what the predictions were, what Spi-M [modelling group] and the others said we would be at this stage given the steps we are taking.
“We are sticking with our plan.”
The Prime Minister urged over-50s to come forward and get their booster jabs as soon as they become eligible. “You get the call, get the jab,” he said.