The transmission of Hand, Foot, and Mouth Disease in East and Southeast Asia

Hand Foot and Mouth Disease (HFMD) is in endemic in many countries in East and Southeast Asia, including those in the tropical or subtropical climate zones. To substantially reduce HFMD, it is necessary to design effective control measures, which is based on a deep understanding of the disease transmission. However, the transmission mechanism of HFMD was rarely studied. The cyclic pattern of HFMD incidence is believed to be related to climatic factors, rather than school terms as observed from childhood infectious diseases in developed countries in the prevaccination era. Furthermore, the association of incidence and climatic factors in different locales in China are inconsistent and even contradictory. Here we selected countries or regions in typical climatic zones in East and Southeast Asia to study the transmission rate and its seasonality for HFMD. Countries or regions selected representing temperate, subtropical and tropical zones are Japan, Hong Kong SAR, Macau SAR and Singapore. Comparatively, we chose provinces in mainland China in three climate zones and contrast them with above selected regions or countries. We used Time Series Susceptible Infected Recovered (TSIR) model to estimate the HFMD transmission rate. The parameters in the TSIR model were estimated by Markov Chain Monte Carlo (MCMC). We then used a linear regression model to analyze the effects of climate factors, seasonal contact rate in children (and seasonal contact rate in population for provinces in China) on the transmission rate of HFMD in selected regions. We found that: 1) transmission rate of HFMD is highly seasonal in the studied countries, SARs and provinces of mainland China, except Singapore; 2) the HFMD transmission rate can be affected by the climatic factors as well as the seasonal contact rate of population, depending on which factor is dominant; 3) The transmission rate in provinces in China increased dramatically during the time period of Chinese Spring Travel Rush that has higher population contact; 4) transmission rate seasonality in Japan, Hong Kong SAR and Macau SAR is affected by climatic factors. Author Summary Hand, Foot and Mouth Disease (HFME) is endemic in East and Southeast Asia with reported cases of more than two million every year. The epidemic patterns such as annual cyclic pattern of reported HFMD cases have been observed and studied for the purpose of understanding the disease. The mechanisms that describe how a disease is transmitted cannot be observed, however they lead to the observed epidemic patterns of the disease. We analyzed the transmission rate (that help to understand the transmission mechanism) of HFMD in selected countries or regions that represent territories in tropical, subtropical and temperate climatic zones in East and Southeast Asia and compared the HFMD transmission in these regions. We also analyzed the possible driving factors of the seasonal transmission of HFMD. The transmission of HFMD can be affected by both social behavior and climatic factors, however either of them can dominant the effect on HFMD transmission depending on regions or countries. In mainland China, high population contact rate is the dominant factor to have high HFMD transmission; while in Japan, Hong Kong SAR and Macau SAR, climatic factors have the dominant effect. These findings can help design effective control measures.