Barghini and de Medeiros general, insects are attracted to lights. However, a common misunderstanding is that this attrac- tion represents a positive phototaxis. Contrary to this belief, Thompson (1917), Verheijen (1958), Mazokhin-Porshnyakov (1969), Janzen (1983), and more recently Nowinszky (2003) observed that insect attraction to lights is the result of navigational confusion. Attraction results when insects mistake light sources (espe- cially those emitting ultraviolet radiation) for the celestial points of reference they normally use for orientation, which may result in a tra- jectory toward a light. In the vicinity of a light source, however, not all insects are directly attracted to the lamp. Although some may be, others may hide in dark places around or near the light, fly in the illuminated area, or land somewhere near the lamp (Nowinszky 2008). Despite all this variation, it is important to stress that even vectors that usually bite only in the dark may be attracted to the surrounding areas of a light source and thus come into close contact to humans where they may transmit diseases in nonconventional ways. For example, Chagas disease was traditionally transmitted by triatomine bug bites, but oral transmission has become common with the advent of electrifica- tion, as we will discuss later. To demonstrate the potential of night lighting for augmenting people’s exposure to vectors and for creating new modes of disease transmission, we performed a review of epide- miological studies that were conducted in rural equatorial regions. We found circumstantial evidence that electrification and lighting may be the source of new modes of transmission for three well-known infectious diseases. Chagas Disease diseases, validated by epidemiologists, came from Chagas disease. This is remarkable, considering that its vectors (triatomine bugs, also known as kissing bugs) do not bite in lighted areas, and artificial lighting has always been considered a good defense against them. Chagas disease was typically found among people living in adobe huts with straw- thatched roofs, excellent hideouts for the bug. It was widespread in pre-Columbian times in the Andean world, where domesticated cui or guinea pigs (Cavia porcellus) were the primary hosts (Coimbra 1988). The main vector was Triatoma infestans—a bug well adapted to households in which sanitary conditions are poor. In colonial times, it had spread to the South American lowlands, and by 1955–1964 the disease had reached central and northern Brazil, probably carried from place to place in the baggage of immigrants. The main vec- tors were T. infestans in Brazil, and Rhodnius prolixus in Venezuela, Colombia, and the Guyanas (Zeledon and Rabinovich 1981). Large-scale insecticide spraying campaigns of households in Brazil after the 1970s and in most of Latin America after the 1980s proved to be effective in controlling Chagas disease in Brazil, but it continues to be a serious epidemic in Bolivia, Peru, Ecuador, and Venezuela. According to Dias et al. (2002), By the end of the last century it became clear that continuous control in contiguous endemic areas could lead to the elimination of the most highly domestic vector populations—especially Triatoma infestans and Rhodnius prolixus—as well as substan- tial reductions of other widespread species such as [Triatoma] brasiliensis, [Triatoma] sordida, and [Triatoma] dimidiata, leading in turn to the inter- ruption of disease transmission to rural people. Ironically, the first confirmation of the strong impact of artificial lighting on the diffusion of While eliminating the most highly domes- tic vector populations, new disease outbreaks Figure 1. Triatomine bugs were attracted by this strong artificial light source at a sugarcane juice kiosk and were crushed together with the sugarcane when the juice was processed, which infected 12 people who consumed the juice. Photograph by L.A. Oliveira Ilha. 1504 ovlume 118 | number 11 | November 2010 • Environmental Health Perspectives arose, with a different pattern of diffusion involving a more diverse group of insect vec- tors and a larger pool of wild and domestic animal hosts. At the same time, a new mecha- nism of human transmission was discovered. Specifically, vectors that are attracted to arti- ficial lighting in areas surrounding homes, instead of entering directly into homes. There, they may rest on plants such as the açai palm (Euterpe oleracea) and parasitize opossums or other warm-blooded animals. As a result, fruits contaminated with their feces may be consumed by people. This form of oral trans- mission is being increasingly observed and may be a consequence of the vector’s attrac- tion to lighting. For example, in February– March 2005 the Department of Health of Santa Catarina (Brazil) identified an epidemic of Chagas disease (Ministério da Saúde 2007). After intensive research, it was verified that sugarcane juice sold at a roadside kiosk was the source of infection for all 12 confirmed cases. The vector of Chagas disease does not live in sugarcane plantations, and there was no reason for it to be in stored sugarcane. The only positive indication was the high-intensity discharge lamp installed at the sugarcane juice kiosk (Figure 1). The bugs (Triatoma tibia- maculata) were attracted by the strong artifi- cial light source in the sugarcane juice kiosk and were crushed together with the sugarcane when the juice was processed, thus transmit- ting the infection. The mechanism of oral transmission was originally proposed by Bertram (1971) and confirmed by Zeledon and Rabinovich (1981), who reviewed experiments on tri- atomine bugs and reported that 20 species— including R. prolixus—were attracted to lights. Many researchers have reiterated this hypoth- esis since then (Cuba et al. 2002; Feliciangeli et al. 2002; Salomon et al. 1999; Teixeira et al. 2001; Zeledon et al. 2001). In many cases reports simply mention the possibility that lighting may have facilitated disease transmis- sion, but Walter et al. (2005) explicitly identi- fied a strong association between the spread of Chagas disease and the use of kerosene lamps and photovoltaic panels. These are modern high-intensity lighting systems to which most insects are attracted. Two recent important reviews of Chagas disease also concluded that artificial lighting may affect transmission of the disease (Remme et al. 2006; Rojas et al. 2005). Remme et al. (2006) described three different transmission cycles, including a domestic cycle involving domestic insect vectors and animal reservoirs that reside in close contact with humans, a sylvatic cycle in which sylvatic-insect vectors transmit the disease to wild animal hosts, and a peridomestic cycle in which sylvatic vectors that are attracted to lights in and around homes transmit infection by feeding on domestic