A five year old female child presented with fever, throat pain and swelling in neck region and was clinically diagnosed as a case of diphtheria and confirmed microbiologically. An epidemiological investigation was conducted, which revealed that the child had received no vaccine against diphtheria. She was managed with antibiotics, anti-diphtheritic anti-sera, DPT and other necessary vaccines as required under UIP. Five other children from the same school were also identified to be sufferring from similar complaints during the same period. All the children were tracked and rapid search for any other similar cases was conducted. History of partial/incomplete immunisation among the close contacts was also obtained and their chemoprophylaxis with oral erythromycin was ensured through government functionaries. No other case of diphtheria has since been reported from this area. This report highlights the steps that need to be adopted for prompt epidemiological investigation of infectious diseases in collaboration with public health authorities to achieve the optimum desired results.  

Key words : Epidemiology, Immunization, DPT vaccine