BACKGROUND: Since the introduction of varicella vaccine, the number of chickenpox cases has dropped significantly in the United States. According to the CDC, surveillance data from 26 states showed that varicella incidence had declined by 82% from 2000 to 2010. This trend is also present in North Dakota. Before this study was implemented, only 21 cases of chickenpox were reported for 2014 in North Dakota compared to 120 cases in 2005. Chickenpox is a reportable condition in North Dakota and all probable and confirmed cases are required to be reported. The decline in cases has been attributed to the introduction of vaccination; however, it is likely that some of the decrease is due to underreporting. In order to ascertain the effectiveness of current reporting practices in the state, records were reviewed from two major health systems in the state in order to identify unreported cases of chickenpox in North Dakota.
METHODS: Two major health systems in North Dakota were identified and requested to participate in retrospective chickenpox case identification. These systems were selected because of their presence in multiple regions of the state, including those most densely populated. In order to identify potential chickenpox cases, a line list of patients was obtained from the billing departments of the facilities. Patients included in the line list had a date of service that fell between January 1, 2014 and June 30, 2015 which was the identified study period. Included patients also must have been diagnosed in a North Dakota facility and have a diagnosis code that pertained to varicella. Each record was then reviewed by an intern who was in the process of obtaining her masters of public health and medical degrees.
RESULTS: A total of 115 records were reviewed to determine if they met the probable or confirmed chickenpox case definition. The project was able to identify 73 cases of probable or confirmed chickenpox; 66 of these cases were not previously reported to the North Dakota Department of Health. Of the 73 cases identified, only four cases were confirmed with laboratory testing while the rest were confirmed by provider diagnosis.
CONCLUSIONS: The results of this project indicate that the majority of chickenpox cases are not reported and that current methods of chickenpox case identification are ineffective. The results suggest a need for education on chickenpox reporting requirements. The absence of laboratory testing also suggests a need for provider education surrounding diagnosis recommendations for chickenpox.