A small study of patients suffering from persistent symptoms long after a bout of Covid-19 found that nearly 60 percent had nerve damage possibly caused by a defective immune response, a finding that could point to new treatments, US researchers reported on Tuesday.

The study involved in-depth exams of 17 people with so-called long Covid, a condition that arises within three months of a Covid-19 infection and lasts at least two months.

"I think what's going on here is that the nerves...