.jpg)
Why do some people get long covid and others don’t?
Why do some people get long Covid after a corona infection and others just a cold? That’s what PhD student Elke Wynberg at GGD Amsterdam and the Amsterdam UMC investigated for three years. “A large group had only mild Covid symptoms and still got long Covid.”
.jpg)
For three years, Elke Wynberg, wearing white pants and a blue blazer, came to be known as the GGD’s “long Covid expert.” During her brief visit to Amsterdam for her doctorate - Wynberg now lives in Thailand where she is starting a postdoc - Folia speaks with her at the Crea student cultural center. “Of course, it is unusual to use the word expert for an area of research about which we still know so little.”
Although no one knew of the existence of lung covid when Wynberg started her PhD thesis. The original idea of the Recoverd-cohort study, a collaboration between Amsterdam UMC and GGD Amsterdam was to follow up patients who became infected with corona. “We wanted to see how symptoms developed over one or two months, but it soon became apparent that in part of the group the symptoms persisted longer,” Wynberg says.
Wynberg eventually followed 349 people infected with corona for two years, starting in May 2020. Half of them were people who reported to the GGD after a positive corona test, while the other half were admitted to the Amsterdam UMC.
Elke, what exactly is long covid?
“Good question, because we are actually still investigating that. According to the definition of the World Health Organization (WHO), you have long Covid when you have one or more symptoms three months after a Corona infection that persist for at least two months, which cannot be explained by any other cause. Those symptoms can vary from shortness of breath, heart palpitations, and loss of smell and taste, to fatigue.”
What makes it so difficult to study long covid?
“Unlike many diseases, long Covid is not confined to one organ system. SARA-CoV-2 affects the intestines, the lungs, the heart, the muscles ... That’s also what makes the clinical picture so varied. In addition, symptoms can disappear and return sometime later. This is incredibly difficult not only for the patient and family members but also as a research subject. It is also difficult to measure where the virus resides in the body. We know that long Covid patients do not test positive for long periods, so the virus probably does not always stay in the nasal and pharyngeal cavities. Other research with intestinal biopsies shows that the virus stays in the intestines in many long Covid patients. But that’s quite an operation, so most lung covid studies do not collect these samples. Also, there are places in the body where you can’t take a biopsy.”
How many people got long Covid in your study?
“We looked at people with severe, moderate, and mild corona infections. Of those, about 80, 60, and 30 percent, respectively, still had one or more symptoms from the infection after three months. On average, 40 percent still had symptoms after one year.”
That’s a lot.
“We also found that surprising, but don’t forget that half of our subjects were hospitalized. That ratio in Amsterdam is different: only a few percent of those who got corona were hospitalized. But, because many people in the Netherlands have had corona at some point, these proportions still mean that there is a large group who have persistent symptoms.”
Is there a correlation between the severity of the corona infection and the risk of long Covid?
“Our study showed that patients with severe corona infections were more likely to develop symptoms, even after adjusting for being overweight, obese, and having co-morbidities. What was more difficult to disaggregate was the effect of ventilators on patients in the ICU. In fact, ventilators can even cause prolonged symptoms of fatigue and shortness of breath. It’s also important to mention that there were also many people in our study who had mild Covid symptoms - sometimes just a cold - who still got long Covid. We didn’t expect that. It also suggests that corona and long Covid have different causes.”
What do researchers now know about the causes of long Covid?
“For now, there are only hypotheses. One is that the multiplication of the virus in the body causes inflammation. Could it be that this inflammation continues to flare up in the body from time to time even after a corona infection? In my research, we investigated that hypothesis by measuring cytokines in long Covid patients. Cytokines are proteins that are elevated in inflammatory responses. It turns out that cytokines are by no means elevated in all long Covid patients. By contrast, when we look at a more specific group, in this case, long Covid patients with lung disease, it turns out that they are.”
What is needed to better investigate long covid?
“The tricky thing is that the definition of long Covid is still so broad. It would help to focus the research by the subcategory of long Covid, for example, long Covid patients with lung issues. Then you can look at the causes in a much more focused way. In addition, it is important that research on lung covid in Africa, South America and Asia is also funded, as most studies so far have been done in Europe and the US.I have already contacted researchers in Thailand who were setting up a study on long Covid to see if we could work together.”
Elke Wynberg received her doctorate on October 4th for her dissertation “Epidemiology and Long-Term Clinical Characteristics of COVID-19 in Amsterdam, the Netherlands. Lessons Learned and Considerations for the Future.”
