A report of the investigation and control measures instituted after the isolation of toxin-producing Corynebacterium diphtheriae mitis from a child in Leeds.

This report describes the control measures instituted and further investigations undertaken after the isolation of toxin-producing Corynebacterium diphtheriae from a throat swab taken routinely from a nine-year-old boy, recently returned from Pakistan, who had been admitted to hospital in Leeds with hepatitis A infection. Four of his siblings were subsequently shown to have identical Corynebacterium diphtheriae on throat swabbing, except that in one child the organism did not produce toxin. All the children were asymptomatic carriers.