The Role of Human Movement in the Transmission of Vector-Borne Pathogens

Abstract

BackgroundHuman movement is a key behavioral factor in many vector-borne disease systems because it influences exposure to vectors and thus the transmission of pathogens. Human movement transcends spatial and temporal scales with different influences on disease dynamics. Here we develop a conceptual model to evaluate the importance of variation in exposure due to individual human movements for pathogen transmission, focusing on mosquito-borne dengue virus.Methodology and Principal FindingsWe develop a model showing that the relevance of human movement at a particular scale depends on vector behavior. Focusing on the day-biting Aedes aegypti, we illustrate how vector biting behavior combined with fine-scale movements of individual humans engaged in their regular daily routine can influence transmission. Using a simple example, we estimate a transmission rate (R0) of 1.3 when exposure is assumed to occur only in the home versus 3.75 when exposure at multiple locations—e.g., market, friend's—due to movement is considered. Movement also influences for which sites and individuals risk is greatest. For the example considered, intriguingly, our model predicts little correspondence between vector abundance in a site and estimated R0 for that site when movement is considered. This illustrates the importance of human movement for understanding and predicting the dynamics of a disease like dengue. To encourage investigation of human movement and disease, we review methods currently available to study human movement and, based on our experience studying dengue in Peru, discuss several important questions to address when designing a study.Conclusions/SignificanceHuman movement is a critical, understudied behavioral component underlying the transmission dynamics of many vector-borne pathogens. Understanding movement will facilitate identification of key individuals and sites in the transmission of pathogens such as dengue, which then may provide targets for surveillance, intervention, and improved disease prevention.

Spatio-temporal patterns of dengue in Malaysia: combining address and sub-district level

“…The most likely outbreak cluster was found to be in the Petaling district. The identified clusters at the sub-district level were close in space and time and may have been driven by human mobility rather than spatial action on the vector part (Stoddard et al, 2009;Teurlai et al, 2012) as there is a relatively high daily movement of commuters across the interconnecting sub-districts (Barter, 2002;Bunnell et al, 2002). The 2010 outbreak clusters in this area (Table 1) confirm the findings by Hassan et al (2012), who associated these clusters with rainfall.…”

The role of population movement in the epidemiology and control of schistosomiasis in Brazil: a preliminary typology of population movement

“…Our research group used electronic personal data assistants and global positioning system (GPS) units to facilitate the tracking of individuals and families who changed residences within rural study communities. The placement of smaller GPS units on individuals has been recommended by Stoddard et al (2009) and Seto et al (2007) as the best option for tracking daily, short-distance movements in rural communities; cellular phones may be used for large-scale studies or studies of regional movements and movements within large urban areas where GPS signals are intermittent. To the best of our knowledge, these and other electronic devices have not been used in research in Brazil.…”

“…However, the determinants, patterns and impacts of this migration are poorly understood. Suitable methodologies and reliable data are limited and, as a result, there have been few rigorous examinations of the epidemiological role of human movement in schistosomiasis and other parasitic diseases (Stoddard et al 2009). Junghanss (1998) examined the relationship between tuberculosis and population movement, but found that the absence of information about underlying circumstances and mechanisms made such a project difficult.…”

“…The paper presents a preliminary typology based on the typology developed by Prothero (1977) to identify some understudied areas and to provide guidelines for further research. Prothero's typology considers causal, spatial and temporal dimensions of individual and group movement and has been employed in the study of various vector-borne diseases in different endemic regions (Stoddard et al 2009). …”

Parasite sources and sinks in a patched Ross–Macdonald malaria model with human and mosquito movement: Implications for control

“…The malaria parasite is found in red blood cells of an infected person, and transmission to humans occurs predominantly through mosquito bites, although according to the CDC [10] "it can also be transmitted through blood transfusion, organ transplant, the shared use of needles or syringes contaminated with blood, or from a mother to her unborn infant before or during delivery (congenital malaria)". Transmission depends on complex interactions between moving mosquito [19], and moving human [28,35,36] populations to facilitate parasite spread.…”