The 2014 measles outbreak in Osaka An epidemiological study for the elimination of measles

To examine and analyze the spread of measles in Osaka in 2014 and determine effective measures to prevent such occurrences.

We analyzed 47 cases of measles reported in Osaka, including one measles patient living in another prefecture where there was an outbreak. We focused on age distribution, the number of patients reported each week, estimated infection routes, history of measles vaccination, detection of viruses, and number of days it took to report the case after the onset of measles.

Patients aged 20-39 years accounted for 24 cases (51.1%). The number of patients reported started from 2nd week with relatively broad peak to 27(th) week, and the measles epidemic was brought under control in the 47(th) week. Among the 47 cases, no source could be identified in 16 cases (34.0%). Household exposure was the main cause of the infection (25.5%), followed by imported cases (21.3%). Eighty-three percent of the overall patients had not received a measles vaccination at all or it was unclear whether they previously had been vaccinated. Genotype B3, H1, and D8 were detected in our patients and these genotypes originated overseas. It took significantly more days, from the onset of measles, for the case to be reported in patients aged 15 years and over compared with those aged under 15 years (P=0.001).

For eradicating measles in Osaka, it is important to raise awareness about this issue among medical institutions, especially institutions for adults, in order for them to report cases as soon as possible, upon discovery in their patients. In addition, "catch-up" supplementary immunizations are effective for all people, including adults who are susceptible to measles.