From the first days of the pandemic, it became clear that some people excreted genetic material from the virus in their feces for months after becoming infected with Covid-19. The findings were initially viewed as curiosity, but there is growing evidence to support the idea that permanent pockets of coronavirus – in the gut or elsewhere – may contribute to long-term covid.
Earlier this month, Prof. David R. Walt and colleagues at Harvard Medical School announced that they had found the Sars-CoV-2 protein – the most common viral spike protein – in the blood of 65% of long-term Covid patients who tested, up to 12 months after their first diagnosis.
Although small in advance, the study provides some of the most compelling evidence to date for the idea that the reservoirs of the virus can contribute to long-term ill health. “The half-life of thorn protein in the body is quite short, so its presence indicates that there must be some active viral reservoir,” Walt said.
Spike protein was not detected in the blood of Covid patients who did not have persistent symptoms.
Walt was motivated to conduct the study after earlier research by his colleagues found genetic material from the Covid virus (viral RNA) in stool samples from children with multisystemic inflammatory syndrome (a rare but serious condition that often occurs around four weeks). after infection with Covid) as well as protein spikes and a marker of intestinal leakage into their blood. Their treatment with a drug that reduces intestinal permeability led to a rapid clearing of the thorn protein and improvement of their symptoms. Walt’s working hypothesis is that something similar can happen to people with prolonged Covid.
If other groups were able to replicate Walt’s findings, it would be a “pretty done game” for the idea that pockets of the virus were not yet present in at least some long-term patients with Covid, said Dr. Amy Proal, a microbiologist at the PolyBio Research Foundation. an American non-profit organization that supports research into complex chronic inflammatory conditions: “I personally do not see a mechanism by which thorn protein could remain for long periods without the virus [being present]”
Other groups have also found evidence that the virus continues to be present – called “viral persistence” – in patients who have recovered from Covid. In April, Ami Bath of Stanford University in California and colleagues reported that about 13 percent of people still excrete viral RNA in their feces four months after becoming infected with Covid, and nearly 4 percent continue to do so every seven months. These people also often report continuing gastrointestinal symptoms such as nausea, vomiting and abdominal pain.
“The question is whether the continued presence of the virus in the gut or elsewhere can tickle the immune system and cause permanent symptoms,” Bhat said.
A separate study that analyzed the intestinal tissue of 46 people with inflammatory bowel disease who had recovered from a mild form of Covid found that viral RNA or protein could still be detected in 70% of them seven months later. Approximately two-thirds of these people report persistent symptoms such as fatigue or memory problems – until none of those without a detectable virus do so.
Yet other preliminary studies have recovered the virus – in some cases a replicating virus – from other anatomical sites, including the eyes, brain and heart, many months after infecting humans.
Viral persistence is also seen in other diseases, such as Ebola, where the virus hides in ‘anatomical refuges’ such as the eyeball or the testicles, which are less accessible to the immune system – and which are thought to contribute to ongoing joint symptoms. and muscle pain or fatigue in many survivors.
However, there is still no conclusive evidence that viral reservoirs contribute to the long Covid and Bhat would like to see further research before reaching this conclusion.
Some of them are already underway. For example, the US National Institutes of Health’s Recover study looked for signs of coronavirus in stool and intestinal tissue samples from people with long-term covid. “These types of research will be crucial to begin to distinguish what the link may be between long-term viral reservoirs and long-term Covid,” Bhat said.
If virus resistance does cause at least some of the symptoms in humans, it may also stimulate the investigation of antiviral drugs as a treatment for long-term Covid. While this may sound pointless, some virologists are concerned about the consequences.
“The idea of giving people long-term antiviral monotherapy to try to clear the virus is quite controversial, because given how much adaptation of the virus we see even for short periods of time, the chance of the virus escaping is extremely high. , ”Said Dr. Deepti Gourdasani, a clinical epidemiologist at Queen Mary University in London. “I think we really need to start thinking about double or triple therapies and try them, because we can’t really afford to create more mutants that have escaped at this point.”
Whether it’s tissue testing or antiviral drug testing, for those who have been living with Covid for a long time, some more than two years, such studies may not come fast enough.
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