Recent Outbreaks of Diphtheria in Dibrugarh District, Assam, India.

Diphtheria is still a significant child health problem in countries with low immunization coverage. Reports of diphtheria in adult population are also increasing. Here we describe three recent outbreaks of diphtheria in Dibrugarh district, Assam in two consecutive years. The study was undertaken in Assam Medical College & Hospital, Dibrugarh after the diagnosis of two Diphtheria cases in the month of September and October 2015 and another in January 2016. Outbreak investigation was done after defining operational definition and throat swabs were collected from thirty three (33) individuals including three (3) index cases and thirty (30) close contacts. Diagnosis was done by clinical findings, direct microscopy, bacteriological culture and in-house designed multiplex Polymerase Chain Reaction (PCR) of the isolates for the expression of Corynebacterium diphtheriae specific rpoB gene and tox gene. Out of the 10 confirmed cases, 2 and 7 were in the first two outbreaks while only one in the third outbreak respectively. All the cases were of age > 10 years, unimmunized or partially immunized. The overall mortality was 20%. PCR results revealed all the culture positive isolates to be tox gene positive. Diphtheria is a resurgent problem in our region with a significant age shift towards adult.