Gut fungi could be contributing to worsening symptoms of long Covid, a study has found, as doctors continue to question why some people struggle to recover from the virus.
Researchers at Weill Cornell Graduate School of Medical Sciences in New York found the growth of intestinal fungi, or mycobiota, led to a surge in immune cells that increased lung damage, or fibrosis, in patients with Covid-19.
During a severe Covid-19 infection, gut-dwelling fungi such as Candida albicans yeast were found to thrive, leading to excessive inflammation that exacerbates disease and causes long-lasting changes to immunity.
Immunologists studied the effects of new viral infections of Covid-19 and found a similar response to that of inflammatory bowel disease, which also triggers harmful inflammation within the body.
Doctors in the UAE said inflammation was common in patients with persistent Covid-19 symptoms.
“It has been observed specifically with the Covid virus that some patients do persist to have lung fibrosis specifically, and this happens because they have inflammation inside the airways,” said Dr Sukhant Bagdia, a pulmonologist at Burjeel Medical City.
“This is common in patients dependent on oxygen in intensive care for a longer period of time, and they are probably getting a secondary infection.
“Some continue to have this fibrosis, restricting their life with shortness of breath, fatigue, malaise and also getting infections more easily.
“The virus has created an inflammatory process, and a small proportion of people would be having this inflammatory reaction beyond control.”
Severe Covid link
Scientists at Weill Cornell tested blood samples from 91 people admitted to hospital with Covid-19 in 2020 and compared them with 36 people who had never tested positive for the virus.
Those with severe Covid were found to have around four times the number of antibodies associated with common gut fungal species.
Dr Iliyan Iliev, an associate professor of immunology at Weill Cornell Medicine, said severe cases of Covid-19 and long Covid were not previously associated with potentially harmful fungal blooms in the intestines.
Researchers found an increase in immune cells called neutrophils in the most severe cases of Covid.
The study then looked at preclinical models involving mice, and found those carrying fungi found in those severely ill patients produced more neutrophils in their blood and lungs.
Giving the mice anti-fungal drugs reduced the inflammation, offering hope a similar treatment could eventually be applied to humans.
The findings could lead to further research, and a more tailored medical approach in the way long Covid patients are treated.
“Several studies proved a Covid infection leads to changes in the gut microbiome,” said Dr Titty Mary Thomas, a family medicine specialist at NMC Royal Hospital, Abu Dhabi.
The microbiome comprises the trillions of bacteria, fungi and other microbes that inhabit the digestive tract.
“These changes can be caused by an infection directly in the gut, as a response to increased inflammation and crosstalk between the oral, lung, and gut microbiome,” said Dr Thomas.
“Unnecessary antibiotic use is the most common and significant cause of major alterations in the body’s natural microbiota.
“When the protective microbiota is disrupted, it may lead to other pathogens to enter the blood leading to serious fungal infections, intestinal inflammation and a prolonged SARS‐CoV‐2 recovery.”
Gut microbiota can be restored using probiotics, to potentially improve rehabilitation, Dr Thomas said.
According to one of the largest studies of long Covid in the UK, one in 20 people diagnosed with the virus were still reporting symptoms 12 months later.
Imperial College London assessed 276,000 people regularly tested for coronavirus as part of the national React surveillance study.
Gut microbes play an important role in regulating intestinal physiology and overall health, and can also impact metabolism, control of ageing and progression of disease.
Dr Niyas Khalid, an internal medicine specialist at Burjeel Medical City, contracted Covid-19 in April 2020, in the early months of the virus, and still has occasional shortness of breath and chest pain on exertion.
“Post-viral fatigue is real, but we had no documented studies that it could last this long until we saw Covid,” he said.
“I have had patients in my clinic who never had any history of asthma in their childhood, or allergies.
“Then suddenly they had Covid and started having asthma out of nowhere.
“The proportion of allergies, and the proportion of asthmatics have gone up post Covid – that could also be attributed to some molecular level changes that could also trigger inflammation inside the body.”
The US Centres for Disease Control and Prevention defined post-Covid conditions as new, returning, or continuing symptoms that people experience more than four weeks after being infected with SARS-CoV-2.
The most frequently reported symptoms are fatigue, cough, shortness of breath, and chest pain. Half of patients report persistent neurological symptoms at six months, the most frequent being “brain fog” and cognitive changes.
“We have also seen cases of very rare fungus like Mucormycosis attacking people who had Covid,” said Dr Khalid.
“This used to only attack immunocompromised people.
“We have seen a rise in those cases, and in people with a history of Covid-19.
“We need to have a systematic study on how this virus has affected our immune system so we can respond as physicians.”