For several years, scientists have tried to untangle one of COVID-19’s persistent puzzles: Why do some people, even after mild infections, go on to develop lasting health issues? And crucially: How do you prevent, treat or even cure those lingering symptoms?
Now, fresh clues are emerging. Several research teams have honed in on potential hallmarks of long COVID, formally known as post-COVID-19 condition, offering insight into the possible mechanisms at play.
Other researchers, meanwhile, are finding overlaps between long COVID and the persistent symptoms some people experience after other types of infections, from influenza to the common cold — suggesting there may be similar triggers for a wide range of little-understood conditions.
There are no smoking guns yet. Still, emerging research could bring scientists one step closer to figuring out treatments to ward off post-infection symptoms ranging from debilitating exhaustion to life-altering “brain fog.”
“We’re getting the sense that there are some tangible mechanisms that can produce some of these symptoms,” said Christoph Thaiss, an assistant professor of microbiology at the University of Pennsylvania’s Perelman School of Medicine.
“And many of them might actually be, surprisingly, shared among many of these conditions.”
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Studies point to long COVID biomarkers
Two recent studies have tried to tease out long COVID biomarkers — traits in someone’s blood, tissues or bodily fluids that can be measured and tracked, at times offering signals of an infection or disease. (Blood pressure and high cholesterol, for instance, are both common biomarkers physicians analyze at routine medical appointments.)
One new paper, from Thaiss and others at the University of Pennsylvania, was published on Monday in the journal Cell. It looked at both real-world patients — some with long COVID, others who fully recovered — and animal models.
Their research suggests the release of interferons — a group of signalling proteins that cells send out as an alert system when there’s a viral threat — could drive the depletion of a key chemical messenger, serotonin. In turn, that may lead to cognitive impacts such as memory issues or a feeling of “brain fog.”
The team was surprised to find that some people with long COVID still had virus fragments lingering in their guts, long after they were no longer testing positive for the virus. Those particles, located through stool samples, might be enough to trigger the release of interferons.
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That could set off a chain reaction, leading to inflammation that makes it tougher for the digestive system to absorb tryptophan — an essential amino acid found in food that helps the body make serotonin.
During long COVID, it seems the “peripheral pool of serotonin is depleted, while the brain pool of serotonin is untouched,” said Thaiss. And when serotonin elsewhere in the body dries up, it can disrupt crucial parts of the nervous system. (Scientists still don’t fully understand how serotonin works, but low levels have previously been linked to depression, along with sleep and digestive issues.)
This new research follows another recent biomarker study from a team led by Yale University immunologist Akiko Iwasaki. That paper, published by Nature, involved a comparison of three groups: people with long COVID, those who were infected around the same time but fully recovered, and those who have never had COVID.
The team found differences in blood samples that distinguished long COVID patients from the others, including exhausted immune cells and lower levels of cortisol, a hormone that regulates a wide variety of bodily processes including metabolism and immune response.
Iwasaki’s team also noticed the reactivation of dormant Epstein-Barr virus (EBV) in long COVID patients. This common pathogen can cause mononucleosis (also known as mono) but also infects most people at least once in their lifetime, usually without any symptoms.
“So now we’re kind of thinking that could be indicative of a person’s immune response being dampened by the COVID infection, allowing these latent viruses to become reactivated,” she said. “It’s also possible that [this] reactivated EBV can be leading to some of the symptoms.”
Research still in ‘early days’
In some ways, these efforts to identify biomarkers are raising more questions than answers. But infectious diseases specialist Dr. William Schaffner, from the Vanderbilt University Medical Center in Nashville — who wasn’t involved in either study — says they do shine a spotlight on potential mechanisms at play.
The question now, he said, is: “Why is it that some people can’t turn off the inflammatory response and it continues to smolder, causing this collateral damage?”
It’s still “early days” when it comes to answering that question, Schaffner added, because the latest published studies are fairly small and narrow in scope, based on researchers’ areas of expertise.
“These various studies seem to complement each other,” he added, “even though they’re not exactly duplicative.”
Schaffner and others are hopeful, however, that these kinds of emerging findings could eventually lead to a diagnostic test for long COVID, or to potential treatments.
The study zeroing in on serotonin, for instance, points to existing medications — selective serotonin reuptake inhibitors (SSRIs), a class of drugs most commonly prescribed to treat depression — as one area for future research.
“The million-dollar question is whether we can treat individuals or ameliorate their symptoms by targeting this pathway — either by restoring serotonin levels, through tryptophan supplementation or through the usage of SSRIs, or by eradicating their viral reservoir,” said Thaiss.
The latest studies come at a time when rates of long COVID appear to be dropping, partly because of widespread use of COVID vaccines. (Matt Rourke/The Associated Press)
But the condition still impacts millions around the world — with a broad range of symptoms and severity — and many scientists say untold numbers of people likely suffered similar ailments after other types of viral or bacterial infections, long before COVID hit.
New research from the U.K. published earlier this month in The Lancet’seClinicalMedicine suggests SARS-CoV-2 isn’t the only respiratory virus that can lead to lasting symptoms after someone gets through an initial infection.
The research team analyzed data from more than 10,000 adults and found evidence of lingering health issues following influenza and common cold infections as well, with some symptoms that overlapped with long COVID and some distinct differences.
Long COVID was linked more often to dizziness and issues with someone’s sense of taste or smell, for instance, while lingering symptoms after a cold were more likely to include gastrointestinal issues.
“The fact that we found some similarities and a few differences to me really indicates that different infections will be able to lead to different sorts of symptoms, and when there’s overlap, we’ll be dealing with a similar mechanism in the end,” said Giulia Vivaldi, a statistician and epidemiologist at Queen Mary University of London who is working on the COVIDENCE U.K. study, a prospective population-based look at respiratory infections.
Iwasaki, from Yale, said the findings were not particularly surprising, and agreed with the research team’s conclusion that post-infection health impacts deserve far more scrutiny, beyond just long COVID.
“We don’t really know the frequency of how other types of viruses lead to post-acute infection syndrome,” she said.
“So that’s something that we need to study further.”
‘We could go back to having a life’
One of the Canadians still grappling with long COVID, Montreal physician Dr. Anne Bhéreur, agreed there are likely various conditions with common links, be it lingering symptoms after certain bacterial infections or the largely unexplained and disabling condition myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).
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Bhéreur has faced an array of symptoms since she had COVID in late 2020, including shortness of breath, difficulty speaking, nausea, dizziness and extreme fatigue.
Various interventions and medications have improved her condition over the years, Bhéreur said, but it’s far from a cure. Even now, over-exertion can bring all her worst symptoms back, years after her initial infection.
Still, she’s hopeful that ongoing research will bring scientists closer to an actual treatment for the root causes of conditions like hers, and potentially other post-infectious illnesses that she says have long been “utterly neglected.”
It could be decades before patients get results, Bhéreur noted — she cited one study suggesting it’s an average of 17 years between research and clinical changes — but she said if momentum holds up, there’s hope for a treatment game-changer.
“Knowing that they could treat the root cause, that we could reverse what’s going on, would also mean we could go back to having a life,” she said.
The Canadian government says it will donate up to 200,000 vaccine doses to fight the mpox outbreak in Congo and other African countries.
It says the donated doses of Imvamune will come from Canada’s existing supply and will not affect the country’s preparedness for mpox cases in this country.
Minister of Health Mark Holland says the donation “will help to protect those in the most affected regions of Africa and will help prevent further spread of the virus.”
Dr. Madhukar Pai, Canada research chair in epidemiology and global health, says although the donation is welcome, it is a very small portion of the estimated 10 million vaccine doses needed to control the outbreak.
Vaccine donations from wealthier countries have only recently started arriving in Africa, almost a month after the World Health Organization declared the mpox outbreak a public health emergency of international concern.
A few days after the declaration in August, Global Affairs Canada announced a contribution of $1 million for mpox surveillance, diagnostic tools, research and community awareness in Africa.
On Thursday, the Africa Centres for Disease Control and Prevention said mpox is still on the rise and that testing rates are “insufficient” across the continent.
Jason Kindrachuk, Canada research chair in emerging viruses at the University of Manitoba, said donating vaccines, in addition to supporting surveillance and diagnostic tests, is “massively important.”
But Kindrachuk, who has worked on the ground in Congo during the epidemic, also said that the international response to the mpox outbreak is “better late than never (but) better never late.”
“It would have been fantastic for us globally to not be in this position by having provided doses a much, much longer time prior than when we are,” he said, noting that the outbreak of clade I mpox in Congo started in early 2023.
Clade II mpox, endemic in regions of West Africa, came to the world’s attention even earlier — in 2022 — as that strain of virus spread to other countries, including Canada.
Two doses are recommended for mpox vaccination, so the donation may only benefit 100,000 people, Pai said.
Pai questioned whether Canada is contributing enough, as the federal government hasn’t said what percentage of its mpox vaccine stockpile it is donating.
“Small donations are simply not going to help end this crisis. We need to show greater solidarity and support,” he said in an email.
“That is the biggest lesson from the COVID-19 pandemic — our collective safety is tied with that of other nations.”
This report by The Canadian Press was first published Sept. 13, 2024.
Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.
HALIFAX – The Nova Scotia government says it could be months before it reveals how many people are on the wait-list for a family doctor.
The head of the province’s health authority told reporters Wednesday that the government won’t release updated data until the 160,000 people who were on the wait-list in June are contacted to verify whether they still need primary care.
Karen Oldfield said Nova Scotia Health is working on validating the primary care wait-list data before posting new numbers, and that work may take a matter of months. The most recent public wait-list figures are from June 1, when 160,234 people, or about 16 per cent of the population, were on it.
“It’s going to take time to make 160,000 calls,” Oldfield said. “We are not talking weeks, we are talking months.”
The interim CEO and president of Nova Scotia Health said people on the list are being asked where they live, whether they still need a family doctor, and to give an update on their health.
A spokesperson with the province’s Health Department says the government and its health authority are “working hard” to turn the wait-list registry into a useful tool, adding that the data will be shared once it is validated.
Nova Scotia’s NDP are calling on Premier Tim Houston to immediately release statistics on how many people are looking for a family doctor. On Tuesday, the NDP introduced a bill that would require the health minister to make the number public every month.
“It is unacceptable for the list to be more than three months out of date,” NDP Leader Claudia Chender said Tuesday.
Chender said releasing this data regularly is vital so Nova Scotians can track the government’s progress on its main 2021 campaign promise: fixing health care.
The number of people in need of a family doctor has more than doubled between the 2021 summer election campaign and June 2024. Since September 2021 about 300 doctors have been added to the provincial health system, the Health Department said.
“We’ll know if Tim Houston is keeping his 2021 election promise to fix health care when Nova Scotians are attached to primary care,” Chender said.
This report by The Canadian Press was first published Sept. 11, 2024.
ST. JOHN’S, N.L. – Newfoundland and Labrador‘s chief medical officer is monitoring the rise of whooping cough infections across the province as cases of the highly contagious disease continue to grow across Canada.
Dr. Janice Fitzgerald says that so far this year, the province has recorded 230 confirmed cases of the vaccine-preventable respiratory tract infection, also known as pertussis.
Late last month, Quebec reported more than 11,000 cases during the same time period, while Ontario counted 470 cases, well above the five-year average of 98. In Quebec, the majority of patients are between the ages of 10 and 14.
Meanwhile, New Brunswick has declared a whooping cough outbreak across the province. A total of 141 cases were reported by last month, exceeding the five-year average of 34.
The disease can lead to severe complications among vulnerable populations including infants, who are at the highest risk of suffering from complications like pneumonia and seizures. Symptoms may start with a runny nose, mild fever and cough, then progress to severe coughing accompanied by a distinctive “whooping” sound during inhalation.
“The public, especially pregnant people and those in close contact with infants, are encouraged to be aware of symptoms related to pertussis and to ensure vaccinations are up to date,” Newfoundland and Labrador’s Health Department said in a statement.
Whooping cough can be treated with antibiotics, but vaccination is the most effective way to control the spread of the disease. As a result, the province has expanded immunization efforts this school year. While booster doses are already offered in Grade 9, the vaccine is now being offered to Grade 8 students as well.
Public health officials say whooping cough is a cyclical disease that increases every two to five or six years.
Meanwhile, New Brunswick’s acting chief medical officer of health expects the current case count to get worse before tapering off.
A rise in whooping cough cases has also been reported in the United States and elsewhere. The Pan American Health Organization issued an alert in July encouraging countries to ramp up their surveillance and vaccination coverage.
This report by The Canadian Press was first published Sept. 10, 2024.
