Scientists have shown a link between the composition of the gut microbiome and the risk of long-term symptoms after contracting COVID-19. The conclusions of the study suggest that modulating the gut microflora may be one way to alleviate the annoying long Covid.
Long-Covid "Long Covid" is a complication syndrome in convalescents, characterized by the fact that COVID-19 symptoms persist for several months after the initial infection. It occurs quite often - 3 out of 4 people who recovered from COVID-19 report at least one bothersome symptom even six months after the disease - most often fatigue, insomnia and muscle weakness.
So far, it is not known why long Covid-19 occurs - the causes of this condition include both an excessive response of the immune system, as well as cell damage and physiological consequences related to comorbid disease. It is also unknown how long Covid occurs and why some people are more susceptible to it.
However, more and more evidence indicates that the relationship with long Covid-19 may be composed of the gut microbiome, i.e. bacteria, fungi and other microorganisms inhabiting the gut. The microbiome has a huge impact on immunity, and disorders of the immune response can affect the healing process.
In a new study, the results of which were published in the Gut journal, prof. Sowing Ng and a team of researchers at The Chinese University of Hong Kong tracked changes in the gut microbiome in 106 patients with varying degrees of COVID-19 severity treated at 3 different hospitals from February to August 2022, and a control group of 68 people who during the same period, they did not have COVID-19. The mean age of patients with COVID-19 infection was 48 years; just over half were women. In 81 percent the infection was mild to moderately severe; 25 people were treated with antibiotics.
Researchers analyzed stool samples collected on admission, at 1 month and 6 months, and in the case of 11 patients - also 9 months later.
For the purposes of the study, long COVID was defined as at least one symptom that persisted for 4 weeks after SARS-CoV-2 was eliminated from the body.
The researchers took into account respiratory and neuropsychiatric symptoms(headaches, dizziness, loss of taste and smell, restlessness, poor concentration, disturbed sleep, depressed mood, poor memory, blurred vision), gastrointestinal, musculoskeletal, skin (hair loss), and fatigue.
Researchers assessed the presence of the 30 most frequently reported long-term COVID symptoms 3 and 6 months after the initial COVID-19 infection. They also used a 6-minute walk test to assess their aerobic capacity and endurance.
Long COVID was reported in 86 (81%) patients after 3 months and in 81 (76.5%) after 6 months. After 6 months, the most common symptoms were fatigue (31%), poor memory (28%), hair loss (22%), anxiety (21%), and sleep disturbances (21%).
Six months after the initial infection, no significant differences were observed between patients with long COVID and those without COVID, in terms of age, gender, incidence of underlying diseases, use of antibiotics or antiviral medications, or the severity of COVID-19 infection.
Researchers noticed that 28 species of intestinal bacteria decreased and increased - 14 in patients with chronic COVID. These changes were found both on admission to hospital and at 3 and 6 months after discharge. Six months after discharge, patients with long COVID had significantly fewer "friendly" F. prausnitzii and Blautia obeum and more "unfriendly" Ruminococcus gnavus and Bacteroides vulgatus than controls.
On the other hand, the gut microbiome of people who did not develop long-term COVID showed only 25 changes in bacterial species on admission to the hospital, and after 6 months it completely recovered.
Further analysis showed that 81 bacterial species were associated with different categories of long COVID symptoms, with many species with more than two categories of persistent symptoms.
For example, after 6 months, persistent respiratory symptoms were associated with the presence of several "bad" microbes, incl. Streptococcus anginosus, Streptococcus vestibularis, Streptococcus gordonii and Clostridium disporicum.
Researchers also showed that 6 months after infection, people with long Covid had a drastically reduced number of species associated with immune enhancement, including Bifidobacterium pseudocatenulatum, F. prausnitzii, R. inulinivorans and Roseburia hominis.
The presence of several "hostile" species of bacteria was associated with inferior performance in the 6-minute walk test among people with long COVID.
On admission to hospital, the diversity and richness of intestinal bacteria inpatients who then developed long COVID was significantly lower than those who did not. The study authors say this means that particular gut microbial profiles may indicate increased susceptibility. According to the researchers, "profiling" the microbiome can help identify those most vulnerable to Covid debts.
"In conclusion, the altered composition of the gut microbiome is strongly associated with persistent symptoms in COVID-19 patients up to 6 months after SARS-CoV-2 virus clearance, the researchers said. "With the millions of people infected during the ongoing pandemic, our findings are a powerful incentive to consider modulating the microflora to facilitate rapid recovery and reduce the burden of acute COVID-19 syndrome."