The distribution of dengue vectors, Ae. aegypti and Ae. albopictus, is affected by climatic factors. In addition, since their life cycles are well adapted to the human environment, environmental changes resulting from human activity such as urbanization exert a great impact on vector distribution. The different responses of Ae. aegypti and Ae albopictus to various environments result in a difference in spatial distribution along north-south and urban-rural gradients, and between the indoors and outdoors. In the north-south gradient, climate associated with survival is an important factor in spatial distribution. In the urban-rural gradient, different distribution reflects a difference in adult niches and is modified by geographic and human factors. The direct response of the two species to the environment around houses is related to different spatial distribution indoors and outdoors. Dengue viruses circulate mainly between human and vector mosquitoes, and the vector presence is a limiting factor of transmission. Therefore, spatial distribution of dengue vectors is a significant concern in the epidemiology of the disease.
Current technologies such as GIS, satellite imagery and statistical models allow researchers to predict the spatial distribution of vectors in the changing environment. Although it is difficult to confirm the actual effect of environmental and climate changes on vector abundance and vector-borne diseases, environmental changes caused by humans and human behavioral changes due to climate change can be expected to exert an impact on dengue vectors. Longitudinal monitoring of dengue vectors and viruses is therefore necessary.

In early 2014, dengue cases were reported from northern Mozambique, 30 years after the last outbreak. We identified potential dengue vector species in three northern towns, Pemba, Nampula and Nacala, and one southern town, Maputo, during the outbreak in April 2014. A major dengue vector species, Aedes (Stegomyia) aegypti, was found in all these towns. The dominant vector subspecies in the northern towns was Aedes aegypti aegypti, while Ae. aegypti formosus was dominant in Maputo. Considering the high proportion of Ae. aegypti aegypti and its high vector competence, the findings from this study suggest that Ae. aegypti aegypti was responsible for the outbreak in northern Mozambique.

In early 2014, dengue cases werereported from the northern Mozambique, 30 years since the last outbreak. Weidentified potential dengue vector species in three northern towns, Pemba, Nampulaand Nacala, and one southern town, Maputo, during the outbreak in April 2014. Amajor dengue vector species, Aedes (Stegomyia) aegypti, wasfound in all these towns. The dominant vector subspecies in the northern townswas Aedes aegypti aegypti, while Ae. aegyptiformosus was dominant in Maputo. Considering the high proportions of Ae. aegypti aegypti and its high vectorcompetence, the findings from this study suggest that Ae. aegypti aegypti was responsible for the outbreakin the northern Mozambique.

Although it is very important in view of public health to understand the mosquito breeding sites and key reservoirs existing around residential areas, such information is lacking in temporary housing sites constructed after the serious tsunami strikes on 26 December 2004 in Sri Lanka. This study clarified the situation regarding mosquito breeding 14 months after the tsunami in Sri Lanka by surveying temporary housing and non-damaged village areas, and also by examining people‘s knowledge related to mosquito breeding sites and mosquito-borne diseases. The relative frequency of mosquito larvae in wastewater pools was significantly higher in temporary housing than in village areas. The prevalence of storage containers at temporary housing and village areas was not significantly different. It was found that wastewater pools in temporary housing sites were the main breeding site of Culex quinquefasciatus Say, Cx. tritaeniorhynchus Giles, and Aedes albopictus Skuse whereas storage containers in village areas were the main breeding site of Cx. quinquefasciatus and Ae. albopictus. No mosquitoes bred in storage containers in the temporary housing but some Ae. albopictus did so in village areas. The questionnaires indicated a significant difference between residents of temporary housing and villages in response to the question: Do you know where mosquitoes breed? The proportion of the “wastewater pools” response was higher among temporary housing residents than among village residents. This knowledge among temporary housing residents may relate to the fact that wastewater pools are latent breeding sites for mosquitoes in temporary housing sites. Although residents in the temporary housing sites put salt and abluent into storage containers to prevent mosquitoes from breeding, wastewater pools receiving a constant supply of wastewater provided the best breeding site for mosquitoes.

A prospective case–control study was conducted in urban districts in Hanoi, northern Vietnam to evaluate the effect of migration on the risk of hospitalisation for dengue in a Vietnamese urban population. We enrolled laboratory-confirmed dengue patients aged >18 years who were hospitalised in local hospitals in November and December 2010. Four neighbourhood-matched controls for each case were recruited within a week of hospitalisation. Sociodemographic data were collected by interviews, and the number of immature and adult mosquitoes within household premises was counted by entomological survey. Matched-pair analyses were conducted using conditional logistic regression models. Among 43 cases and 168 controls, 84% and 83% were migrants from rural areas, respectively. Although statistical significance was marginal, recent migration (residing in study area for <5 years) independently increased the risk of hospitalisation for dengue compared with inhabitants after controlling for potential confounders (adjusted odds ratio [aOR] = 3.78; 95% confidence interval [CI] = 0.99–14.27), whereas longer-term migration (residing in study area for >6 years) did not change the risk (aOR = 1.1; 95% CI = 0.30–4.05). Younger age (18–34 years) (aOR = 7.26; 95% CI = 2.39–22.06) and higher adult Aedes aegypti infestation level within household premises (aOR = 9.25; 95% CI = 1.68–51.09) were also independently associated with hospitalisation for dengue. Recent migration from rural areas seems to increase the risk of hospitalisation for dengue in urban populations in endemic areas. Further research including cohort study should be done to confirm the impact of migration on the risk of dengue in urban areas.