An infectious disease expert says the latest research suggesting stress is a major factor causing long Covid makes biological sense, but cautions more studies are needed.
New Zealand's Dr Richard Webby is a prominent infectious diseases researcher at St Jude Children's Research Hospital in Memphis, Tennessee.
Photo: Supplied/St Jude Hospital
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He told Sunday Morning that a Harvard University study suggesting people who were under stress before contracting Omicron could be at higher risk of developing long Covid gelled with what was known about how stress could impact a body's behaviour.
"We know that stress does alter the way your body behaves a little bit and so these cytokines that your body produces during times of stress, it's these same molecules that also control - to some degree - your immune response."
But he said studies looking at the long-term consequences of viral infections were "really hard to do" and more research would be needed across different populations to ascertain how robust the study's findings were.
"These studies are ... really hard to do well and the literature is a little bit mixed in terms of what long Covid is and in terms of what causes it."
Covid-19 was not alone in causing post-infection problems for people, he added.
"You could do a Google search of long flu - you probably wouldn't come up with much but there have been studies that link influenza infection with other diseases, if you like, that aren't respiratory, so heart disease and other sort of cardiovascular syndromes."
Although influenza and Covid-19 infected people in slightly different ways, Webby believed there was "some overlap" in how acute respiratory viruses could set people up for "other symptoms down the road".
"I think Covid has some properties that are unique in terms of what it can do but I would suggest that a lot of what we're seeing is not necessarily Covid-specific and if people really looked hard enough, they may see some of these similar signatures with things like flu, perhaps RSV (respiratory syncytial virus) and some of these other respiratory viruses that hit us most winters."
He said that, as predicted, Omicron continued to mutate and his "gut feeling" was that it would be "another season or two" before the virus settled into any more predictable pattern of behaviour.
"This really isn't a common cold virus - at least not at this stage; we may end up there but that's not where we are right now.
"This virus ... can cause a lot of pretty severe disease, acutely and subsequent to infection ... right now I think the impact of it is pretty high - at least up there with flu."
It remained to be seen whether New Zealand would experience a summer wave of infections driven by new Omicron variants, Webby said, but additional waves were certainly expected as the northern hemisphere headed into winter.
The virus' "end game" likely wouldn't be reached until more people had been exposed to it multiple times, he said.
"We really have to wait until that happens before we know the answer to: 'what does Covid look like moving forward'."