Comparison of contact patterns relevant for transmission of respiratory pathogens in Thailand and the Netherlands using respondent-driven sampling

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

IgG-ELISA Antibody Titers against Japanese Encephalitis (JE) and Dengue Virus Type 1 among Healthy People in JE-endemic Areas in Japan and Thailand

日本脳炎流行地である日本の熊本県とタイ国のチェンマイにおける健康住民の日本脳炎ウイルス(JE)とデングウイルス1型(D1)に対する抗体価を免疫酵素測定法(ELISA)により測定した.熊本の検体のD1に対するIgG-ELISA抗体価はJEに対する価に比べて低値側に分布し,わずかに50才以上の検体がD1に対し高い値を示したにすぎなかった.一方チェンマイの成人はJEとD1両抗原に対しほぼ同程度のIgG-ELISA抗体価を保有していた.Antibody titers against Japanese encephalitis (JE) and dengue virus type 1 (Dl) were measured by enzyme-linked immunosorbent assay (ELISA) among healthy people in JE-endemic areas in Japan (Kumamoto Prefecture) and Thailand (Chiang Mai Province). The IgG-ELISA titers against Dl in Kumamoto distributed in lower range as compared with those against JE, although some people over 50 years of age possessed relatively high IgG-ELISA titers against Dl antigen. On the other hand, adult people in Chiang Mai possessed similar titers against these two antigens as measured by IgG-ELISA

Factors associated with pneumococcal vaccination in elderly people: a cross-sectional study among elderly club members in Miyakonojo City, Japan

Abstract Background Pneumonia 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. Methods We 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. Results A 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). Conclusions Although 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

Online respondent-driven sampling for studying contact patterns relevant for the spread of close-contact pathogens: a pilot study in Thailand

Background: Information 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 Methods: We 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.Results: We 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.Conclusions: Despite 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

Correlations between any two linked individuals in the same network tree.

<p>Correlations between any two linked individuals in the same network tree.</p

Correlations between directly linked individuals in one component.

<p>^a One case who reported >500 household contacts was removed.</p><p>^b Based on total number of self-reported symptoms by each respondent.</p

Number of recorded contacts by different characteristics.

<p>^a Most seeds provided a postal code from a district far away from Bangkok, however we assume that most of these students stayed in a student dorm in Bangkok during the study week.</p

Characteristics study populations and recruitment.

<p>Characteristics study populations and recruitment.</p

Egocentric contact data.

<p>(<b>A</b>) Box and whisker plot showing the median, quartiles and 95 percentiles of numbers of contact persons reported by participants for travelling, at different locations and while eating, during weekdays (WD, Monday-Friday) and weekend days (WE, Saturday-Sunday). Dutch sample is indicated in green and Thai sample in purple. (<b>B</b>) Distribution of the overall reported numbers of contact persons (“degree”) in each country. The green solid line (the Netherlands) and the dotted purple line (Thailand) indicate the fitted negative binomial distributions for reported degree. (<b>C</b>) Quantile-Quantile plot of the degree distributions displayed in plot 3B. (<b>D</b>) The probability estimates of inviting recruitees (“intention to recruit”) as a function of degree, specified by sex (and additionally adjusted for variables age, education and household size). Dotted lines indicated confidence intervals (95%). Values were obtained using logistic regression analysis for the full sample and the sample excluding seeds (i.e. sample without wave 0).</p