Understanding infection dynamics of respiratory diseases requires the identification and quantification of behavioural, social and environmental factors that permit the transmission of these infections between humans. Little empirical information is available about contact patterns within real-world social networks, let alone on differences in these contact networks between populations that differ considerably on a socio-cultural level. Here we compared contact network data that were collected in the Netherlands and Thailand using a similar online respondent-driven method. By asking participants to recruit contact persons we studied network links relevant for the transmission of respiratory infections. We studied correlations between recruiter and recruited contacts to investigate mixing patterns in the observed social network components. In both countries, mixing patterns were assortative by demographic variables and random by total numbers of contacts. However, in Thailand participants reported overall more contacts which resulted in higher effective contact rates. Our findings provide new insights on numbers of contacts and mixing patterns in two different populations. These data could be used to improve parameterisation of mathematical models used to design control strategies. Although the spread of infections through populations depends on more factors, found similarities suggest that spread may be similar in the Netherlands and Thailand.

BackgroundInformation on social interactions is needed to understand the spread of airborne infections through a population. Previous studies mostly collected egocentric information of independent respondents with self-reported information about contacts. Respondent-driven sampling (RDS) is a sampling technique allowing respondents to recruit contacts from their social network. We explored the feasibility of webRDS for studying contact patterns relevant for the spread of respiratory pathogens.Materials and MethodsWe developed a webRDS system for facilitating and tracking recruitment by Facebook and email. One-day diary surveys were conducted by applying webRDS among a convenience sample of Thai students. Students were asked to record numbers of contacts at different settings and self-reported influenza-like-illness symptoms, and to recruit four contacts whom they had met in the previous week. Contacts were asked to do the same to create a network tree of socially connected individuals. Correlations between linked individuals were analysed to investigate assortativity within networks.ResultsWe reached up to 6 waves of contacts of initial respondents, using only non-material incentives. Forty-four (23.0%) of the initially approached students recruited one or more contacts. In total 257 persons participated, of which 168 (65.4%) were recruited by others. Facebook was the most popular recruitment option (45.1%). Strong assortative mixing was seen by age, gender and education, indicating a tendency of respondents to connect to contacts with similar characteristics. Random mixing was seen by reported number of daily contacts.ConclusionsDespite methodological challenges (e.g. clustering among respondents and their contacts), applying RDS provides new insights in mixing patterns relevant for close-contact infections in real-world networks. Such information increases our knowledge of the transmission of respiratory infections within populations and can be used to improve existing modelling approaches. It is worthwhile to further develop and explore webRDS for the detection of clusters of respiratory symptoms in social networks.

BackgroundPneumonia is the third leading cause of death in Japan. All elderly people aged 65 years or older are recommended to receive a pneumococcal vaccine. A subsidy for part of the cost of routine pneumococcal vaccination in this age group was introduced in 2014. Factors related to vaccination behavior among elderly adults have not been well reported. The purpose of this study was to investigate factors associated with vaccine uptake among elderly people in Japan.MethodsWe conducted a cross-sectional study, using a self-administered questionnaire among elderly club members aged 65 years or older in one city of Japan in April 2017. The participants were selected from among all elderly club members in the study area. Variables extracted from the questionnaire were analyzed using logistic regression analysis.ResultsA total of 208 elderly club members participated in the study. The mean age (± SD) was 77.2 (± 5.3) years. The pneumococcal vaccination rate was 53.2%. Logistic regression analysis revealed three variables that had a significant association with pneumococcal vaccination: a recommendation for vaccination from medical personnel (aOR 8.42, 95% CI 3.59–19.72, p <  0.001), receiving influenza vaccination in any of the previous three seasons (aOR 3.94, 95% CI 1.70–9.13, p = 0.001), and perception of the severity of pneumonia (aOR 1.23, 95% CI 1.03–1.48, p = 0.026).ConclusionsAlthough the pneumococcal vaccination rate in this study was increased compared with previous reports, almost half of study participants had not yet received vaccination. Our findings could be helpful for developing vaccination strategies to increase the vaccine coverage in the elderly population.Electronic supplementary materialThe online version of this article (10.1186/s12889-018-6080-7) contains supplementary material, which is available to authorized users.

Dengue is an infectious disease prevalent in Sri Lanka. Some factors may influence preventive behaviors. This cross-sectional study aimed to determine the knowledge, attitude, and preventive behaviors associated with dengue and analyzed the factors influencing preventive behaviors among housewives in Colombo, Sri Lanka. The analytical study was designed, and data were collected using a structured questionnaire. The χ(2) test and binary logistic regression were used to analyze data. The mean age of housewives was 39.41 years, 91% were married, 52% were Buddhist, and 46.5% had a family monthly income of 15 000 to 25 000 rupees. The knowledge of dengue preventive behaviors was 69.2%. The majority (91.5%) had a positive attitude toward dengue prevention. Only 39.3% used a mosquito net, and 89.3% had water storage container covers. Overall, 58.5% were knowledgeable about preventive measures. Age, religion, family income, education, knowledge, and attitude were associated with preventive behaviors. These findings are useful for dengue control in Colombo.

BackgroundIn June 2013, the fear of adverse events compelled the government to withdraw its recommendation of the Human papillomavirus (HPV) vaccine.Since then, the rate of vaccination among Japanese girls has dropped dramatically.ObjectiveThis study aims to assess how the Japanese government’s policy change against HPV vaccination influenced the degree to which parents in remote areas in Japan accepted the vaccine for their daughters, and to analyze related factors. MethodsA self-administered questionnaire was distributed to parents with daughters attending secondary schools or high schools in two remote areas of the country. ResultsOut of 700 eligible parents, 246 (35%) responded. The percentage of parents in the “accept group” (those whose daughters had already been vaccinated or those who intended to have their daughters vaccinated) dropped from 54% before the government withdrew its HPV vaccine recommendation to only 4.5% after the withdrawal (1.5% of whom intended to vaccinate and 3% of whom had already had their daughters vaccinated). Vaccine acceptance was higher in parents who were employed as healthcare workers, had been educated through to the completion of high school, had good levels of knowledge about cervical cancer and the HPV vaccine, had low perceived barriers against the HPV vaccine, and received high levels of social support. ConclusionThe acceptance of HPV vaccination among parents was low overall. Higher acceptance may be possible if the government restores its recommendation and healthcare providers disseminate appropriate information about the HPV vaccination and cervical cancer.

Abstract:A cross-sectional survey of 327 Japanese short-term travelers (!3 weeks) arriving in Bangkok, Thailand was conducted to assess the incidence of travelers' diarrhea (TD) as well as their symptoms and treatment-seeking behaviors. The incidence of the first episode of TD (FTD) was ascertained retrospectively by questionnaire. Reported by 69 travelers, FTD clustered within the first 8 days of arrival in Thailand, and the incidence rate varied from 2% to 8% with the highest incidence on the third day.Cumulative probability of FTD was 19% for those arriving in Thai directly from Japan, 42 % for those arriving via Southeast Asia, and 25% for those arriving via other regions at Day 7 by the Kaplan-Meier survival analysis. Log rank test revealed a higher FTD risk for travelers arriving via other Southeast Asian countries than for those arriving directly from Japan (P < 0.005). Of all the 69 FTD episodes, 33% had classic TD defined as "3 unformed stools per 24 hours with at least one accompanying symptom, 49% had moderate TD defined as !2 unformed stools with at least one additional symptom or more unformed stools without additional symptoms, and 17% had mild TD defined as with !2 unformed stools without additional symptoms. Cumulative probability of FTD at Day 7 was 12% for classic TD, 25% for classic plus moderate TD and 30% for all the TD. More than 38% of travelers with diarrhea took medicine brought from Japan. Among travelers with classic TD, 35% bought medicine in Thailand, whereas 47-50% of travelers with moderate and mild TD took only rest without any treatment.

SUMMARY: Dengue viruses were isolated in a mosquito cell clone, C6/36, and their serotypes were identified by the immune adherence hemagglutination (IAHA) test. Even when viruses were not cytopathogenic, the IAHA test detected virus growth in the cells.

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