The first outbreak of measles was reported from the Talaja urban area during the month of January and the second outbreak was reported from Gorkhi village in the month of March. We obtained the measles weekly reporting data from the Integrated Disease Surveillance Project (IDSP) unit to confirm the outbreak. We defined a case clinically by the WHO criteria as the occurrence of a febrile rash with or without cough, coryza and conjunctivitis in a resident of Talaja-urban and the Gorkhi village of the Talaja block in the period from 1st December 2010 to 30th April 2011. We initiated an active case search by conducting house-to-house visits to identify the cases that met the case definition or by stimulated passive surveillance in the aforementioned two-affected areas which had a total population of 9140.

We line-listed the case patients and described them in terms of the person, place and the time characteristics. We also collected information on their age; sex; place of residence; symptomatology, date of onset of the illness, the treatment which was taken, the immunization status of the case patients, the susceptible population and assessment of the cold chain system. We mapped the areas by the location of the households to show the distribution of the cases by their residences in Gorkhi village [Table/Fig-1]. We calculated the attack rate of the cases by their age and sex groups by using the population data which was obtained from the district health authorities. We examined the dynamics of the outbreaks by constructing an epidemic curve.

We collected estimates of the measles vaccine coverage from the district head. We also estimated the vaccine coverage in the population by using the data which was gathered from the mothers’ interviews, immunization card reviews and the health care facility records reviews during the field visits. We adopted a retrospective cohort design to estimate the vaccine efficacy. We selected as the study population, the affected patients that were in the age group of 10 months to 15 years. We calculated the preventable fraction of the children among those who were exposed (i.e., those vaccinated) to obtain the vaccine efficacy. We used the following formula for the cohort study: (attack rate among non-vaccinated - attack rate among vaccinated) / attack rate among non-vaccinated (The formula used was ARU−ARV/ARU*100). We entered and analyzed the data by using an MS-Excel sheet.

We explained the purpose of collecting the samples and the processing of the samples to the population of the study areas. We collected 5 samples from the affected population for testing the specimens for the IgM/IgG antibodies by using ELISA. We assigned identification numbers and labeled other epidemiological details on all the samples. We transported the specimens to B.J Medical College, Ahmedabad India, in a reverse cold chain separately. The samples were only taken from those who were willing, while the reluctant/refusing populations were dropped.

[Table/Fig-1]:

Spot map of measles outbreak in Gorkhi village of Bhavnagar district, Gujarat, India 2011

In our study, we identified 27 confirmed cases of measles in the urban area of Talaja and 78 cases in Gorkhi village. There was a 75% increase in the measles cases as compared to those in the previous year. All the 105 case patients belonged to the age group of 3months-15 years. The ages of the case patients ranged from 2-7 years in the Talaja urban area, whereas the age range was 3 months-15 years in Gorkhi village. The Attack Rate (AR) was highest among the children who were aged 5 to 9 years in both the areas [Table/Fig-2]. None of the areas reported a sex wise statistically significant difference in the attack rate. A history of febrile rash was present in the all-case patients. According to their mothers’ statements, out of the 105 case patients in the 2 areas, 40 (38%) case patients were immunized. The block health administration organized a special measles catch-up program with the support of the district authority in the month of March 2011.

There was a sporadic distribution of the case patients in the households. In the first outbreak in the Talaja-urban area, the index case which was identified in the area was reported on 8th January 2011; and the maximum number of cases (80%) was reported in the second week of January, one incubation period after the migration of two cases which had travelled from Bhavnagar city. The second outbreak which got the index case on 18th March in Gorkhi village, reported the highest number of cases in the final week of March. One death was reported during the second outbreak. The dynamics of the two outbreaks in the epidemic curve [Table/Fig-3] indicated that there were a number of generations of cases, with the propagated outbreak. The number of cases declined during the second week of January 2011 in the first outbreak, and the second outbreak ceased in the second week of April 2011. The acute cases of measles were given vitamin A supplementation and supportive treatment by the health staff.

A total of 10 sera from five case-patients each from both the areas were tested; all were found to be positive for the IgM/IgG antibodies by ELISA.

The Attack Rates (ARs) of measles by the age and the vaccination status indicated that there were 21 case patients among the 740 non immunized children as compared to 6 case patients among the 2620 immunized children in the urban area of Talaja; while in the Gorkhi village, the ARs of measles by the age and the vaccination status indicated that there were 36 case patients among the 375 non immunized children as compared to 33 case patients among the 1326 immunized children; and both were statistically significant (P <.001) [Table/Fig-4].

This outbreak occurred in the rural and the urban area of Bhavnagar, India in 2011. The outbreaks of measles in the rural and the urban areas were reported from various states of India [9, 13-15]. Measles is generally an endemic disease with sporadic outbreaks. An outbreak is said to occur when the number of cases which are observed is greater than the number which is normally expected in the same geographic area for the same period of time. We identified 105 measles case patients during this outbreak, which confirmed the measles outbreak. In the present study, the highest no of measles cases was found in the 5-9 years age group, suggesting an age shift from the younger children [14] to the old age group. Similar observations were made by Mishra et al. [16] The attack rate was higher in Gorkhi village (44 per 1000 pop.) as compared to Talaja urban (27 per 1000 pop.). This can be explained on the basis of the higher number of susceptible individuals in the previous area. [Table/Fig-3]

We used the outbreak investigation method to find out the measles vaccine efficacy. The vaccine efficacy in the urban area was 92% but in the Gorkhi village, it was only 73%. The lower efficacy might be due to a recall bias, but it warrants the requirement of a second dose opportunity for measles.

The present double outbreak is due to the progressive accumulation of a small number of susceptible children in the community over the years. Such accumulations are typically caused by the combination of the following 2 factors: (1) the measles vaccine efficacy not reaching the level of 100% and (2) the children being left un-immunized each year. We found that the participation of people in the routine immunization for measles was poor due to the injectable vaccine and the low level of awareness about the importance of the immunization. We had organized community awareness programmes along with the local community leader to raise awareness and to increase their participation in the catch-up campaign; this resulted in the immunization of 158 children who were previously unimmunized because of the refusal by their parents.

The United Nation’s Millennium Development Goal 4(MDG4) aims at reducing the overall number of deaths among children by two-thirds between 1990 and 2015 [17]. The measles and rubella initiative contributed 23% of the overall decline in the under five years deaths between 1990 and 2008 [18]. If India wants to progress towards MDG4, then the measles control is a must. The strategy for global measles and rubella eradication envisages achieving and maintaining high levels of the population immunity by providing a high vaccination coverage with the two doses of the measles vaccines. Till the introduction of the second dose of the measles vaccine in the National Immunization Schedule of India, strengthening of the routine vaccination should be the cornerstone of the measles control, to achieve a >90% coverage. This can be achieved by identifying the population which is without an access to the routine coverage, raising the community awareness on the need for the vaccination and providing sustainable outreach services. In addition, a measles ‘catch-up’ mass immunization campaign should be conducted to interrupt the chains of transmission and to prevent outbreaks. The catch-up campaign is envisaged to reduce the transmission of measles to very low levels and to thereby protect the infants as they lose their maternal antibodies [19].

The limitation of this study was that we could not obtain the data regarding the migrating population, which would have helped us in improving the present findings.

The measles outbreak that affected the Talaja block was due to factors like refusal by the community, poor hygiene, misbeliefs and illiteracy. Supplementary immunization activities and vitamin A supplementation, as a part of the outbreak control measures, were implemented in both the outbreaks to reduce the morbidity and the mortality, which could result in the control of the outbreak.

The authors have called for the attention of the public health practitioners to a simple methodology of the case detection and analysis that generates information for action - in terms of creating public awareness, increasing the immunization coverage and calling attention to the changes in the trends with regards to the most affected age groups.

However, this investigation was conducted in the context of a public health response to an outbreak, and therefore an ethical committee review was not indicated.