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◆Measles situation update, epidemiologic week 48, 2013 － epidemiologic week 8, 2014
During epidemiologic weeks 1-8, 2014 (December 30, 2013 to February 23, 2014), 119 cases of measles were diagnosed (see latest epidemiologic curve of measles: https://www0.niid.go.jp/niid/idsc/idwr/diseases/measles/measles2014/meas14-08.pdf ), indicating a greater than three-fold increase relative to the same period in the previous year. As of February 28, 2014, 83 cases have been genotyped for measles virus (for more information, see isolation/detection of measles virus in Japan http://www.niid.go.jp/niid/en/iasr-measles-e.html).
During epidemiologic week 48, 2013 to epidemiologic week 8, 2014 (November 25, 2013 to February 23, 2014), as of March 4, 2014, 139 cases of measles were diagnosed, nearly a three-fold increase relative to the 48 cases diagnosed during the same period in the previous year. Seventy-three of the cases were male, with a mean age of 15.2 years (median 11 years, range 4 months to 51 years). During epidemiologic week 8, 2014, a case of encephalitis associated with measles infection was reported. Among the 75 cases with complete notification information that have been genotyped, 72 were B3, two were D8 and one was D9.
The number of cases reported by prefecture during this period was as follows: Kyoto (n=25), Chiba (n=17), Tokyo (n=16), Saitama (n=14), Kanagawa (n=12), Aichi (n=11), Hiroshima (n=9), Hyogo (n=8), Osaka (n=6), Okayama (n=4), Ibaraki (n=3), Miyazaki (n=3); 2 cases were reported from each of the following: Shizuoka, Yamaguchi, and Fukuoka; and 1 case was reported from each of the following: Niigata, Nagano, Mie, Shiga, and Okinawa. Transmission occurred domestically in 90 cases (65%), domestic/overseas in 1 case (1%), unknown in 1 case (1%), and the remaining 47 (34%) having report of transmission overseas, with the largest proportion from the Philippines (Philippines (n=38), Indonesia (n=2), Sri Lanka (n=2), and 1 each from Australia, Guam (United States), India, United States and Vietnam/Malaysia) (Figure). Among the 139 cases, 114 (82%) had either no or unknown history of measles vaccination.
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Since week 48, the number of reported measles cases has been increasing. While there was a high proportion of imported cases until week 48, the proportion of domestic cases has since increased. The proportion of those believed to have been infected overseas was 8% (16/210) during weeks 1-47, 2013, 41% (28/68) during week 48, 2013 to week 4, 2014, and 27% (19/71) during weeks 5-8, 2014. In effect, while recent measles activity started from imported cases, transmission domestically in some areas led to further circulation of the virus within the country. The current situation warrant attention, and indeed, at least 7 reported cases were believed to have been infected in a healthcare setting.
Regardless of age, measles is a potentially fatal disease and warrant vigilant attention. In addition, while there is no specific treatment, prevention is possible through immunization. Japan has achieved substantial progress toward measles elimination. Working toward elimination by 2012, there has been an estimated 97% decline in incidence since 2007-2008 when measles predominated among adolescents; the next target is achieving certification of measles elimination in 2015. It is imperative that imported cases continue to be monitored, and at the same time, to be alert against secondary transmission from imported cases. Thus, there is a need to respond to each case rapidly with epidemiologic investigation; additionally, measles vaccination (ideally MR vaccine) should be systematically implemented among those susceptible, particularly those who are targeted for routine immunization (age one year, one year period prior to elementary school attendance). Furthermore, immunization is also recommended for those in healthcare, education, or welfare who have not received two doses of MR vaccine. While voluntary, such vaccination is beneficial for both public health and personal protection. Travellers overseas should confirm their vaccination status and ensure that they are up to date with the necessary vaccines (immunization through MR vaccine can also provide protection against rubella), preventing importation.
Healthcare workers should continue to carefully investigate symptomatic persons regarding their travel, contact and immunization histories. In addition, particularly in areas where measles has been confirmed, it is imperative that healthcare facilities implement infection control. For ill persons who suspect they may have become infected with measles after coming in contact with persons with fever and/or rash, notification should be made prior to visiting a health facility to prevent secondary transmission. While measles is transmissible via air and serious, it is preventable by vaccination―the increasing re-occurrence of measles calls for strict vigilance.
For more information regarding measles, including previous trends, please visit http://www.niid.go.jp/niid/ja/diseases/ma/measles.html.
Infectious Disease Surveillance Center,
National Institute of Infectious Diseases
Takuri Takahashi, Tomimasa Sunagawa, Hitomi Kinoshita, Kazuhiko Kanou, Takehito Saito, Yuzo Arima, Hiroaki Ito, Kazutoshi Nakashima, Yuichiro Yahata, Satoru Arai, Hiroshi Sato, Keiko Taya and Kazunori Oishi | |
