A Covid-19 nasal swab test punctured a US woman's brain lining, causing fluid to leak from her nose and putting her at risk of life-threatening infection, doctors reported in a medical journal Thursday. The patient, who is in her 40s, had an undiagnosed rare condition and the test she received may have been carried out improperly, a sequence of improbable events that means the risk from nasal tests remains very low. But her case showed health care professionals should take care to follow testing protocols closely, Jarrett Walsh, senior author of the paper that appeared in JAMA Otolaryngology–Head & Neck...