Yellow fever population is vaccinated. Control of the yellow fever mosquito "A. aegypti" is of major importance, especially because the same mosquito can also transmit dengue fever and chikungunya disease. "A. aegypti" breeds preferentially in water, for example in installations by inhabitants of areas with precarious drinking water supply, or in domestic waste, especially tires, cans, and plastic bottles. These conditions are common in urban areas in developing countries. Two main strategies are employed to reduce mosquito populations. One approach is to kill the developing larvae. Measures are taken to reduce the water accumulations in which the larvae develop. Larvicides are used,
Yellow fever 10 years. Although the WHO on 17 May 2013 advised that subsequent booster vaccinations are unnecessary, an older (than 10 years) certificate may not be acceptable at all border posts in all affected countries. A list of the countries that require yellow fever vaccination is published by the WHO. If the vaccination cannot be conducted for some reasons, dispensation may be possible. In this case, an exemption certificate issued by a WHO-approved vaccination center is required. Although 32 of 44 countries where yellow fever occurs endemically do have vaccination programmes, in many of these countries, less than 50% of their