Long COVID no different to other post-viral syndromes?

Long COVID may be no different to other post-viral syndromes, suggests latest research led by Queensland’s Chief Health Officer Dr John Gerrard.

People who tested positive for COVID-19 a year ago were no more likely to report moderate-to-severe functional limitations than people who had influenza, the research found.

Gerrard suggests it is time to stop using terms like “long COVID” as it wrongly implies there is something unique and exceptional about longer-term symptoms associated with the virus. “This terminology can cause unnecessary fear, and in some cases, hypervigilance to longer symptoms that can impede recovery,” Gerrard said.

The study by Queensland Health researchers suggests that in the highly vaccinated population of Queensland exposed to the Omicron variant^[1], long COVID’s impact on the health system is likely to stem from the sheer number of people infected with SARS-CoV-2 within a short period of time, rather than the severity of long COVID symptoms or functional impairment.

Symptoms reported with the illness include fatigue, brain fog, cough, shortness of breath, change to smell and taste, dizziness and rapid or irregular heartbeat.

COVID-19 and influenza

The research, to be presented at this year’s European Congress of Clinical Microbiology and Infectious Diseases (ECCMID 2024) in Barcelona, Spain (27–30 April), adds to previous research by the same authors and published in BMJ Public Health which found no difference in ongoing symptoms and functional impairment when COVID-19 was compared with influenza,12 weeks post-infection^[2].

To understand more about the impact of long COVID on the Australian state of Queensland, researchers surveyed 5112 symptomatic individuals aged 18 years and older, comprising those with PCR-confirmed infection for COVID-19 (2399 adults) and those who were PCR negative for COVID-19 (2713 adults: 995 influenza positive and 1718 PCR negative for both but symptomatic with a respiratory illness) between 29 May and 25 June 2022.

Laboratory reporting for COVID-19 and influenza is mandated upon PCR test request under Queensland’s public health legislation, with the results recorded in the state’s Department of Health’s Notifiable Conditions System. A year after their PCR test, in May and June 2023, participants were asked about ongoing symptoms and the degree of functional impairment using a questionnaire delivered by SMS link.

Overall, 16% (834/5112) of all respondents reported ongoing symptoms a year later and 3.6% (184) reported moderate-to-severe functional impairment in their activities of daily life.

After controlling for influential factors including age, sex and First Nation status, the analysis found no evidence that COVID-19-positive adults were more likely to have moderate-to-severe functional limitations a year after their diagnosis than symptomatic adults who were negative for COVID-19 (3.0% vs 4.1%).

Moreover, results were similar when compared with the 995 symptomatic adults who had influenza (3.0% vs 3.4%).

Physiological data

Jeremy Nicholson, Professor of Medicine and Director of the Australian National Phenome Center at Murdoch University, said the research reports a year follow-up on 5112 symptomatic adult COVID-19 patients (omicron sub-variant of the SARS CoV-2) and 995 post-influenza patients from Queensland Australia. “The study indicates that 3–4% of people have significant symptoms a year after either COVID-19 or influenza, hence the authors argue that they are effectively the same.”

“Unfortunately, this question cannot be simply answered in this work. The study is observational, based on reported symptoms with no physiological or detailed functional follow-up data. Without laboratory pathophysiological assessment of individual patients, it is impossible to say that this is indistinguishable from flu-related or any other post-viral syndrome,” Nicholson said.

“Also, there are many long-term effects of COVID-19 that do not have significant early-stage symptoms eg, heart disease, atherosclerosis and diabetes. These conditions do, however, have associated metabolic signatures which were not measured in the current study.

“The absence of evidence is different from evidence of absence, so the authors’ assertion that long COVID is the same as flu-related post viral syndrome is not proven, even if long COVID is indeed a post-viral syndrome (which it is),” Nicholson said.

Physician training programs

Marie-Claire Seeley from the Australian Dysautonomia and Arrhythmia Research Collaborative at the University of Adelaide and CEO of The Australian POTS Foundation said, “This abstract reveals a significant finding: approximately 4% of individuals, irrespective of the virus they contracted, may experience persistent health issues post-infection, resulting in chronic incapacitation. This implies that long COVID is not a standalone condition but rather part of a broader spectrum of post-viral syndromes.

“These findings align with previous Australian research published in the American Journal of Medicine in 2023. Adelaide researchers objectively demonstrated that 79% of long COVID patients met the criteria for postural orthostatic tachycardia syndrome (POTS), an autonomic nervous system disorder. Considering that POTS typically emerges following viral infection, this correlation is not unexpected. However, it’s concerning because POTS significantly impairs quality of life and functional capabilities, particularly affecting women during their childbearing years.

“Of further concern is the absence of specialised public autonomic physician training programs in Australia, unlike in the USA. This leaves us ill equipped to manage the increasing burden of post-COVID chronic autonomic disorders.”

Further research needed

Interestingly, the Queensland Health analysis also found that those who were more likely to report moderate-to-severe functional impairment were those aged 50 years or older, and those who had symptoms of dizziness, muscle pain, shortness of breath, post-exertional malaise and fatigue.

“These findings underscore the importance of comparing post-COVID-19 outcomes with those following other respiratory infections, and of further research into post-viral syndromes,” Gerrard said.

The authors caution that the findings are associations and do not represent prevalence. They point to several limitations, including that participants who were hospitalised or had pre-existing illness were not identifiable within the cohort. They also note that the risk of long COVID has been lower during the Omicron wave compared with other SARS-CoV-2 variants, and because 90% of people in Queensland were vaccinated when Omicron emerged, the lower severity of long COVID could be due to vaccination and/or the variant.

^{[1] More than 90% of the population of Queensland had been vaccinated against COVID-19 before the community first experienced transmission of the Omicron variant in 2022.
[2] Ongoing symptoms and functional impairment 12 weeks after testing positive for SARS-CoV-2 or influenza in Australia: an observational cohort study (bmj.com)}

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