The tip of the iceberg: incompleteness of measles reporting during a large outbreak in The Netherlands in 2013–2014

Abstract

Measles is a notifiable disease, but not everyone infected seeks care, nor is every consultation reported. We estimated the completeness of reporting during a measles outbreak in The Netherlands in 2013–2014. Children below 15 years of age in a low vaccination coverage community (n = 3422) received a questionnaire to identify measles cases. Cases found in the survey were matched with the register of notifiable diseases to estimate the completeness of reporting. Second, completeness of reporting was assessed by comparing the number of susceptible individuals prior to the outbreak with the number of reported cases in the surveyed community and on a national level. We found 307 (15%) self-identified measles cases among 2077 returned questionnaires (61%), of which 27 could be matched to a case reported to the national register; completeness of reporting was 8.8%. Based on the number of susceptible individuals and number of reported cases in the surveyed community and on national level, the completeness of reporting was estimated to be 9.1% and 8.6%, respectively. Estimating the completeness of reporting gave almost identical estimates, which lends support to the credibility and validity of both approaches. The size of the 2013–2014 outbreak approximated 31 400 measles infections.

Effect of vaccination on severity and infectiousness of measles during an outbreak in the Netherlands, 2013–2014

“…During this outbreak, only 9% of measles cases were notified [29], consistent with the underreporting estimated in the previous outbreak [30,31]. The proportion of complications and hospitalisations among all infected individuals might be lower than the proportion among notified cases when taking the underreporting into account.…”

Additional Evidence on Serological Correlates of Protection against Measles: An Observational Cohort Study among Once Vaccinated Children Exposed to Measles

“…Yet, the attack rate of MV infection in our study was high and our study participants were enrolled in Orthodox Protestant primary schools. As Orthodox Protestants between four and 12 years of age were the most affected group during an outbreak of about 30,000 MV infections [45], we can assume that the majority in our study population was indeed exposed to measles. Furthermore, the results did not change when we limited the analyses to children with highest likelihood of exposure to MV.…”

Epidemics, Air Travel, and Elimination in a Globalized World: The Case of Measles

“…This model is also sensitive to data limitations, particularly with reported measles cases (often underestimated and underreported [44][45][46][47] ) and reported importation cases (required for validation). For an imported case to be reported, the person must either (1) seek medical care, be diagnosed, then be reported by the provider, or (2) be linked to secondary cases who sought care.…”