A new US study is the latest to identify several factors that make some people more susceptible to prolonged Covid than others. However, with millions of people around the world experiencing debilitating symptoms weeks or months after being first infected, the medical establishment still doesn’t understand why.
A new study from the University of Southern California (USC) found that patients who were obese at some point before contracting Covid-19 have a higher risk of developing Covid for a long time.
The researchers also found a link between specific symptoms seen during initial infection and the likelihood of long-lasting Covid, with sore throats, headaches and hair loss indicating symptoms persist months later.
The World Health Organization (WHO) defines prolonged Covid as the presence of symptoms that last for at least two months and cannot be explained by another diagnosis following the coronavirus infection. WHO notes that common symptoms include fatigue, shortness of breath and cognitive dysfunction, and that symptoms may change or recur over time.
Since medical professionals first became aware of the long Covid phenomenon in 2020, scientists and researchers have been puzzled by the different profiles of susceptible patients and researchers have tried to provide a definitive answer.
Research points to a list of possible predictors, including repeated antibodies to Covid infections, high viral load infections, the presence of dormant Epstein-Barr virus, the presence of autoimmunity and lack of vaccination.
Some studies are also contradictory. A USC study found no association between prolonged Covid and age, race or gender, and a June 2022 study funded by Johnson & Johnson found that women were “significantly more likely” to develop prolonged Covid syndrome.
“At the start of 2020 we didn’t know anything,” says Rebecca Livingstone, clinical lead physiotherapist for the post-Covid service at University College Hospital London.
“Our thinking and understanding around long-term Covid has definitely progressed and research is helping us put some of the pieces of the puzzle together. But the more we discover, the more we realize that we still don’t know everything.”
“People think they don’t have it.”
Meanwhile, Covid is affecting millions of people around the world.
A UK study found that in June 2022, an estimated 2 million people were living with prolonged Covid. A USC study found that one in four people with coronavirus infections will still report symptoms for up to 12 weeks. A May 2022 study in Wuhan, China found that half of people hospitalized with Covid still had at least one symptom two years after infection.
The numbers are huge because the Covid-19 virus is highly contagious. In the past two years, more people have contracted Covid than the common cold or the seasonal flu.
But even these figures may be underestimated. “People think they don’t have it,” says Ruth Ainley, a respiratory physiotherapist and long-time Covid specialist. “They think they’re always tired because they’ve got the virus, so they don’t put two and two together.”
Even if people think they are bad, some people are more likely to seek medical help than others. “The data we have says that over a long period of time, the majority of people with Covid are women, they’re middle-aged and they’re white,” says Livingston.
“These data also reflect the people we see in the clinic, and we know there are significant inequities in access to health care, so it may not fully reflect the full picture.”
News articles often focus on the prolonged Covid shock that leaves young, healthy and athletic people with debilitating symptoms. And people with very active lifestyles are more likely to notice and take these symptoms seriously than older people.
“Older people are very poorly diagnosed,” says Ainley. “It’s been ruled out because they haven’t recovered from Covid, or are a bit tired, and that’s to be expected at their age.”
“Hard picture to put together”
Even among patients with long-standing Covid, the complex nature of the disease makes analysis difficult. According to the American Medical Association, there are more than 200 recognized symptoms of prolonged Covid, which estimates that approximately 20-30% of patients are affected even after a mild illness.
And there are some recognizable patterns in when symptoms appear or how long they may last.
“When we started working with people post-Covid, we valued them and expected them to fit into categories. But the truth is much more ambiguous, says Livingston. “People have symptoms that affect many different systems, and some people have some symptoms and not others. It’s very difficult to piece together the picture.”
The impact of prolonged Covid on the lives of many patients is significant. As well as physical symptoms, a 2022 National Institutes of Health study found that a “significant” number of patients — more than a third — experienced PTSD, anxiety or depression three months after the onset of symptoms.
“Every day you see some really heartbreaking moments,” says Livingston. “It’s a really tough situation to live in.”
Waiting for the “aha moment”.
Looking to the future, there is some hope.
Ainley compares the Covid-19 virus and the long struggle to understand Covid to the early experiences with HIV, when little was known about how to treat the virus or how it spread. “Now HIV disease is not a death sentence like before, but it lasted for 30-40 years. The problem with prolonged Covid is that we’re two years into it and we don’t understand enough of the mechanisms behind how it works. ”
Livingston expects that as more representative data about who has had Covid over a longer period of time comes to light, more patterns will emerge to shed new light on who is susceptible.
“Each study is breaking down, and it’s helping us develop our understanding,” says Livingstone. “I’d like to think that at some point in the future there will be an aha moment. You have to hope for that when you’re a clinician or a patient.”
As cases continue to rise in Europe and the United States, taking precautions to prevent Covid infection in the first place is still the best line of defense.
And for those suffering from the disease, research may soon provide much-needed answers. “There’s research to study why people experience things, but we need to study how we treat people and how we help people recover,” says Livingston.
“Prolonged Covid is something that we will have to think about and treat for a long time. But we know that people are recovering and that there are rehabilitation methods that can help people.