Recommended case classifications of diphtheria
A probable case of diptheria is a case that meets the clinical description of an illness characterized by laryngitis or pharyngitis or tonsillitis, and by an adherent membrane of the tonsils, pharynx and/or nose.
Confirmed case
A confirmed case is a probable case that is laboratory confirmed or linked epidemiologically to a laboratory-confirmed case of isolation of Corynebacterium diphtheriae from a clinical specimen, or fourfold or greater rise in serum antibody (but only if both serum samples were obtained before the administration of diphtheria toxoid or antitoxin).
Surveillance of diphtheria consists of a routine monthly report of probable or confirmed diphtheria cases; and immediate investigation of all diphtheria outbreaks with collection of case-based data. Monitoring the number of infants who have received the third dose of diphtheria toxoid-containing vaccine (DPT3) is also important. In countries with low incidence (usually where coverage is >85%–90%) immediate reporting of case-based data of probable or confirmed cases is recommended from peripheral level to intermediate and central levels.