Outbreak of Human Metapneumovirus in Ibaraki, Japan and Its Descriptive Epidemiology

Introduction: The Infection Control Law in Japan does not cover monitoring of human metapneumovirus (HMPV). Therefore, its epidemiology is not well known. However, rapid diagnostic testing for this virus has been reimbursed by public health insurance in Japan since 2014. One case of acute encephalitis caused by HMPV was reported in April 2017 in Ibaraki. All schools in Ibaraki prefecture started to participate in the (Nursery) School Absenteeism Surveillance System ((N)SASSy) in 2009. All nursery schools started to use it in 2012. Methods: We specifically examine its seasonality and incidence by age. The study period extends from October 1, 2014 through May 31, 2017. Results: In total, (N)SASSy received 187 cases during the period. Spring and early summer were apparently the high season. The highest incidence was 36 cases in April 2015. The incidence among zero and one year olds was higher in 2017 than in the same season among 2014-2016. The necessary effort to download data from (N)SASSy, show these figures, and confirm the situation and background was a few minutes. Discussion: Rapid diagnostic testing for HMPV elucidated its epidemiology for the first time. Moreover, timely information sharing through (N)SASSy led the Ibaraki prefectural office to publish a reminder in July 2017 about the HMPV outbreak situation and to encourage precautions against it by nursery schools.

Descriptive Epidemiology for <i>Mycoplasma pneumoniae</i>Infection Using (Nursery) School Absenteeism Surveillance System, and Proposal for Countermeasures

Objective: We present descriptive epidemiology of Mycoplasma infection using the (Nursery) School Absenteeism Surveillance System ((N)SASSy) in addition to national official sentinel surveillance for infectious diseases (NOSSID). It is expected to be helpful for early detection and response to outbreak of Mycoplasma infection and also to be useful for antimicrobial resistance measures. Method: The study period was 2010-2014 seasons. The study area was the whole of Ibaraki prefecture, Japan. NOSSID reports the number of patients with Mycoplasma pneumonia from 13 sentinel hospitals. We compare the number of patients and the incidence rate of NOSSID with the same information in (N)SASSy. Result: In NOSSID, the largest number of patients by age was 27 patients of one year old in 2012. (N)SASSy showed that the incidence rate in the elementary schools is high in 2011 and 2012. Especially, the second grade students were the highest. Discussion: Even though Mycoplasma infection is well known as a pediatric disease, we showed that second grade was the highest in incidence at first. Because (N)SASSy is timely and real-time information collection, evaluation and sharing countermeasures with (nursery) schools, public health centers, and physicians are useful for students and nursery school children, and communities. Conclusion: Because mycoplasma infection is common pediatric infectious diseases and because some patients rarely develop severe infections, we must prevent larger outbreaks. (N)SASSy can provide timely intervention at the initial phase of outbreak by monitoring situations in (nursery) schools and comparing data to baseline information.