Latitude-based approach for detecting aberrations of hand, foot, and mouth disease epidemics

Abstract

BackgroundEpidemics of hand, foot and mouth disease (HFMD) among children in East Asia have been a serious annual public health problem. Previous studies in China and island-type territories in East Asia showed that the onset of HFMD epidemics evolved with increased latitude. Based on the natural characteristics of the epidemics, we developed regression models for issuing aberration alerts and predictions.MethodsHFMD sentinel surveillance data from 2008 to 2014 in Japan are used in this study, covering 365 weeks and 47 prefectures between 24 and 46° of north latitude. Average HFMD cases per sentinel are standardized as Z rates. We fit weekly Z rate differences between prefectures located in the south and north of a designated prefecture with linear regression models to detect the surging trend of the epidemic for the prefecture. We propose a rule for issuing an aberration alert determined by the strength of the upward trend of south–north Z rate differences in the previous few weeks. In addition to the warning, we predict a Z rate for the next week with a 95 % confidence interval.ResultsWe selected Tokyo and Kyoto for evaluating the proposed approach to aberration detection. Overall, the peaks of epidemics in Tokyo mostly occurred in weeks 28–31, later than in Kyoto, where the disease peaked in weeks 26–31. Positive south–north Z rate differences in both prefectures were clearly observed ahead of the HFMD epidemic cycles. Aberrations in the major epidemics of 2011 and 2013 were successfully detected weeks earlier. The prediction also provided accurate estimates of the epidemic’s trends.ConclusionsWe have used only the latitude, one geographical feature affecting the spatiotemporal distribution of HFMD, to develop rules for early aberration detection and prediction. We have also demonstrated that the proposed rules performed well using real data in terms of accuracy and timeliness. Although our approach may provide helpful information for controlling epidemics and minimizing the impact of diseases, the performance could be further improved by including other influential meteorological factors in the proposed latitude-based approach, which is worth further investigation.

Association between meteorological factors and reported cases of hand, foot, and mouth disease from 2000 to 2015 in Japan

“…Causative pathogens of HFMD, such as EV-A71, CA16, and CA6, may affect the disease duration or epidemic peaks [34, 35]; however, in the present study, there was no information available on these pathogens. Under this condition, the use of equations (1) and (2) in this study enabled us to efficiently examine whether HFMD transmission in the 47 prefectures was related to meteorological factors.…”

Epidemiological characteristics of hand, foot, and mouth disease in China

“…Studies have shown that latitude can affect the prevalence of HFMD to some extent. [ 7 ] The incidence of HFMD is relatively high in low latitudes such as the tropics and temperate zones. In addition, many meteorological factors such as high temperature, low pressure, and abundant precipitation are also closely related to the incidence of HFMD.…”

Temperature and humidity affect the incidence of hand, foot, and mouth disease: a systematic review of the literature – a report from the International Society of Dermatology Climate Change Committee

“…reported on case rates in 31 Chinese provinces and found the earliest peak in April (in the southern tropical province of Hainan) and the latest peak in July (in the northernmost province of Heilongjiang, located in the middle temperate zone) . Investigators in Japan used a latitude‐based approach to predict outbreaks in Tokyo based upon disease activity in Kyoto, a city located at a lower latitude and in which outbreaks tend to occur earlier in the calendar year . Lee et al .…”

“…Since May of that year, HFMD has been a mandatory reportable disease to Chinese surveillance systems, which require reporting of suspected cases within 24 hours . Multiple large‐scale outbreaks have also been reported in Japan in the years 2000 (205,365 cases), 2003 (172,659 cases), 2011 (347,407 cases), and 2013 (303,339 cases) . In Cambodia, a particularly virulent strain of EV71 was determined to be responsible for the deaths of at least 54 children between April and June of 2012 .…”

“…Countries at higher latitudes, such as Finland, Japan, the United States, and South Korea, tend to have a single peak of disease during the year, while two peaks have been observed in countries with subtropical and tropical climates such as Singapore, Malaysia, and Taiwan . Peaks also tend to move in a northward direction over the course of a season; countries such as Japan usually experience a peak in the summer, with peaks in the city of Kyoto occurring slightly earlier than those in Tokyo, located further to the north . Likewise, the peak in Finland generally occurs in early autumn …”