Infection with the virus that causes Covid-19 can trigger an adverse immune response that lasts well beyond the initial infection and recovery even among people who had mild symptoms or no symptoms at all, according to a new study published in the Journal of Translational Medicine.

It found that people with prior infection with SARS-CoV-2, the virus that causes Covid-19, have a wide variety of auto-antibodies up to six months after they have fully recovered.

“These findings help to explain what makes Covid-19 an especially unique disease,” said researcher Justyna Fert-Bober from Cedars-Sinai Medical Center in the US.

“These patterns of immune dysregulation could be underlying the different types of persistent symptoms we see in people who go on to develop the condition now referred to as long Covid-19,” Bober added.

The study said that when people are infected with a virus or other pathogen, their bodies unleash proteins called antibodies that detect foreign substances and keep them from invading cells.

In some cases, however, people produce autoantibodies that can attack the body’s organs and tissues over time.

For the study, the team recruited 177 people with confirmed evidence of a previous infection with SARS-CoV-2. They compared blood samples from these individuals with samples taken from healthy people before the pandemic.

All those with confirmed SARS-CoV-2 infection had elevated levels of auto-antibodies.

Some of the autoantibodies also have been found in people with diseases in which the immune system attacks its healthy cells, such as lupus and rheumatoid arthritis.

“We found signals of auto-antibody activity that are usually linked to chronic inflammation and injury involving specific organ systems and tissues such as the joints, skin and nervous system,” said another researcher.

Some of the autoantibodies have been linked to autoimmune diseases that typically affect women more often than men. In this study, however, men had a higher number of elevated auto-antibodies than women.