Seven children infected with hepatitis B were recently expelled by a top middle school in China despite a national ban on discrimination against the estimated 120 million Chinese who carry the hepatitis B virus. An attempt by their parents to sue education authorities over discrimination has foundered after heavy pressure from local officials. Activists involved in the case say prejudice against infected individuals has grown in recent years amid confusion about how hepatitis B is transmitted and widespread advertising of treatments that have stoked public fears about the disease.