A series of new studies on the novel coronavirus showed results that the infection can could the development of antibodies that wrongly target the patient's own tissues instead of the virus.
Aside from warping the body's defenses in many ways such as disarming the body's early warning systems, the latest study, published this week online, indicates that months after the infection has resolved, so-called autoantibodies will linger, perhaps causing irreparable damage, reports the New York Times.
With only nine patients, five of whom had autoantibodies for at least seven months, the newest study is tiny. It has not yet undergone peer review for publication and the authors urged caution in interpreting the findings.
However, if the result is confirmed by other researches, some of the residual symptoms in people who have recovered from Covid-19 can be clarified. The syndrome may involve dementia, "brain fog" and joint pain, often referred to as long Covid.
Autoantibodies are not new to science: They are the misguided soldiers of the immune system, tied to debilitating diseases such as lupus and rheumatoid arthritis, which arise when the body attacks its own tissues.
"It's a signal; it is not definitive," said Dr Nahid Bhadelia, medical director of the special pathogens unit at Boston Medical Center, who led the study. "We don't know how prevalent it is, and whether or not it can be linked to long Covid."
The question of autoimmunity following coronavirus infection is urgent and important, Dr. Bhadelia added. As many as one in three survivors of Covid-19 say they still experience symptoms.
"This is a real phenomenon," she said. "We're looking at a second pandemic of people with ongoing potential disability who may not be able to return to work, and that's a huge impact on the health systems."
A growing body of evidence suggests that autoimmunity contributes to the severity of Covid-19 in some people. A study published online in October found that among 52 patients with severe Covid-19, more than 70 percent carried antibodies against their own DNA and against proteins that help with blood clotting.
In another study, also published online in October, researchers discovered autoantibodies to carbohydrates made by the body in Covid-19 patients, which could explain neurological symptoms. And a study in the journal Science Translational Medicine in November found that half of patients hospitalized for Covid-19 had at least transient autoantibodies that cause clots and blockages in blood vessels.
The gathering research raises the worrying possibility that lingering autoantibodies might lead to autoimmune disease in some people infected with the coronavirus.
"Once these autoantibodies are induced, there is no going back," said Akiko Iwasaki, an immunologist at Yale University. "They will be a permanent part of the person's immune system."
She added: "What does it do to vaccine response? What does it do to newly acquired infections? These are all questions that will have to be addressed."
Dr Iwasaki's team showed in December that severely ill patients had dramatic increases in a wide array of autoantibodies that target parts of the immune system, brain cells, connective tissue and clotting factors.