Two Highly Immunized Hilly Areas versus Double Measles Outbreak Investigations in District Kangra, Himachal Pradesh, India, in 2006.

BACKGROUND: We investigated two sequential outbreaks of measles in seven villages of Kangra, to confirm the diagnosis and to formulate recommendations for prevention and control.

METHODS: We defined a case of measles as occurrence of fever with rash in a child aged six months to 17 years during the period 3(rd) September to 23(rd) November 2006. We collected information on age, sex, residence, date of onset, symptoms, signs, treatment taken, traveling history and vaccination status. We described the outbreak by time, place and person. We estimated vaccine coverage and efficacy in the affected villages. We confirmed diagnosis clinically, serologically and through genotyping of the virus.

RESULTS: We identified 69 cases. Overall attack rates ranged between 4.2% and 6%. All case patients were between 6 years to 11 years of age. Age-specific attack rate in double outbreaks ranged in between 1.7% and 21.6%, the highest being in the age range 11-17 years. No deaths or complications were reported. The epidemic curve was suggestive of typical propagated pattern. The first outbreak imported virus after an interschool game competition (relative risk, 6.44%; 95% confidence interval, 3.81-10.91); followed by the second outbreak, in which people exchanged foods in the festival in one infected village of the first outbreak (relative risk, 5.3; 95% confidence interval, 1.90-14.77; P <.001). The calculated immunization coverage (93%) coincided nearly with administrative claims. The vaccine efficacies were estimated to be 85% and 81% in the first and second outbreaks respectively. Eleven of the 16 case patients were tested for measles IgM antibodies, while two nasopharyngeal swabs were positive by polymerase chain reaction (PCR) and are genotyped D4 measles strain. Vitamin A supplementations were only given in four villages.

CONCLUSION: Measles outbreaks were confirmed in high-immunization-coverage areas. We recommended (i) second dose opportunity for measles in Himachal Pradesh and (ii) vitamin A supplementation to all the case patients.