Measles Outbreak in High Risk Areas of Delhi: Epidemiological Investigation and Laboratory Confirmation.

Objective: To describe epidemiological and laboratory characteristics of the measles outbreaks recorded in the urban slums of Delhi (designated as high risk areas under the Polio program), from February through July 2014.

Methods: As a part of surveillance and containment measures, an extensive field investigation for measles case search (WHO definition) through 'house to house survey' was conducted by district health teams and field volunteers of National Polio Surveillance Project (NPSP), WHO, Delhi from February through July, 2014. The data generated by the health teams was collected and analyzed.

Results: About 1.1 million households in the high risk areas of Delhi were surveyed for epidemiological investigations. A total of 1337 suspected measles cases were reported. The case fatality rate (CFR) was 1.2 %. Statistical analysis showed significant relation between age of the child (measles case) and immunization status. Higher numbers of reported cases were above 5 y and less than 9 mo of age. Measles IgM was detected in 132 cases and D8 strain was isolated on genotyping.

Conclusions: The outbreak was predominantly localized to the high risk areas (urban slums) of the city. Low CFR was reported during the outbreaks. The outbreaks highlight the need to extend the reach of immunization services to urban slums and strengthen measles surveillance including laboratory based surveillance.