Controlling the mosquito that’s largely responsible for infecting people with the dengue fever virus isn’t easy. That’s because the bug, Aedes aegypti, has evolved in parallel with humans, living around them and breeding in even the smallest puddles of water — rainwater in a discarded can, say, or the saucer under a flower pot. With so many potential breeding sites, spreading pesticide can be a painstaking, door-to-door activity. But Gregor J. Devine of Rothamsted Research, an agricultural institute in Britain, had a different idea: why not let the mosquitoes do the work? Building on laboratory studies that showed that adult mosquitoes could pick up an insecticide and transfer it, he and his colleagues conducted field experiments in Iquitos, Peru, using pyriproxyfen, a compound that kills larvae but is not harmful to adult mosquitoes (or to people, either, in the amounts used). After getting a meal of blood from a human, a female A. aegypti likes to find a dark, damp spot to rest while its eggs develop, buzzing off later to find water to deposit the eggs in. Dr. Devine said their work, described in The Proceedings of the National Academy of Sciences, took advantage of this routine. He and his team set up “dissemination stations,” consisting of dark, damp cloths dusted with pyriproxyfen, in the nooks and crannies of above-ground tombs in a cemetery. When a female rested on the cloth, its legs picked up some of the pesticide, which came off when it later landed in a breeding pool. The researchers found that putting stations in as little as 3 percent of the available spots in the cemetery resulted in coverage of almost all the breeding habitats in the immediate area, and mortality of up to 98 percent of the mosquito larvae. Dr. Devine said the technique may be useful for controlling A. aegypti in conjunction with other eradication methods and may also help control mosquito species that spread other diseases, like malaria.

After decades of warnings about the inevitability of another pandemic of influenza, it is astonishing that health officials have failed to make clear to the public, even to many colleagues, what they mean by the word pandemic. Generations of people have used the term to describe widespread epidemics of influenza, cholera and other diseases. But as the new H1N1 swine influenza virus spreads from continent to continent, it is clear that a useful definition is far more complicated and elusive than officials had thought. And what is at stake is far more than an exercise in semantics. A clear understanding of the term is central to the World Health Organization’s six-level staging system for declaring a pandemic, which in turn informs countries when to set their control efforts in motion. Dictionaries and medical journals offer little guidance. Their definitions can be too vague or too narrow, contradictory and clouded by jargon. “There is a lot of misinformation in the medical literature, and it is really quite hard to figure out what is and what is not a pandemic,” said Dr. David M. Morens, an epidemiologist at the National Institute of Allergy and Infectious Diseases who has been studying the history of pandemics. The word implies the rapid spread of an infectious disease to many countries in different regions, hitting each with more or less the same severity. But in fact, severity varies — not all people are infected at the same time, and not every country need be affected. And there can be many other factors, including the numbers and percentages of people falling ill and dying; a population’s vulnerability to the disease, based on previous rates of infection; and the quality of health care facilities and disease monitoring systems. Not least is that scientists do not know precisely how pandemics arise, what fuels them, why they vary in their lethality, why some occur in waves and why they stop.

The number of dengue cases in Argentina reached 25,833, Argentine Health Ministry said on Friday. Despite 3,107 more people have been infected with the disease since the last report was released on April 30, Argentine authorities said the dengue epidemic is being controlled. From February to April, the country has seen a large number of mosquitoes of all kinds, including the Aedes aegypti, which is a carrier of dengue. The northern province of Chaco, where 10,796 cases have been registered, is the worst hit area in the country. While in Catamarca, another northern province, 8,703 cases have been registered.

Current and projected rainfall reduction in southeast Australia has seen the installation of large numbers of government-subsidised and ad hoc domestic water storage containers that could create the possibility of the mosquito Ae. aegypti expanding out of Queensland into southern Australian's urban regions. By assessing the past and current distribution of Ae. aegypti in Australia, we construct distributional models for this dengue vector for our current climate and projected climates for 2030 and 2050. The resulting mosquito distribution maps are compared to published theoretical temperature limits for Ae. aegypti and some differences are identified. Nonetheless, synthesising our mosquito distribution maps with dengue transmission climate limits derived from historical dengue epidemics in Australia suggests that the current proliferation of domestic water storage tanks could easily result in another range expansion of Ae. aegypti along with the associated dengue risk were the virus to be introduced.

'Drought-proofing' Australia's urban regions by installing large domestic water tanks may enable the dengue mosquito Aedes aegypti to regain its foothold across the country and expand its range of possible infections, according to a new study published May 5 in the open-access journal PLoS Neglected Tropical Diseases. Dr Nigel Beebe and colleagues from the University of Queensland, CSIRO Entomology, the Australian Army Malaria Institute, and the Communicable Diseases Branch of Queensland Health, Brisbane, challenge the common assumption that climate change will drive the spread of this mosquito, suggesting instead that the real driver is human behavior. The study combines current and forecasted climate change conditions with historical epidemics to reveal the risk of dengue infections in all capital cities around Australia by 2050. Beebe and colleagues developed and critically assessed their models to project the distribution of the mosquito in 2030 and 2050. Currently, dengue fever occurs in Queensland only. However, the implementation of new water tanks, combined with already warm summer temperatures, could enable the mosquito to re-emerge and further its current reach.