An Anopheles stephensi mosquito shortly after obtaining blood from a human (the droplet of blood is expelled as a surplus). This mosquito is a vector of<unk> , and mosquito control is an effective way of reducing its incidence. Methods used to prevent<unk>  include medications, mosquito elimination and the prevention of bites. As of 2020, there is one vaccine for<unk>  (known as RTS,S) which is licensed for use. The presence of<unk>  in an area requires a combination of high human population density, high anopheles mosquito population density and high rates of transmission from humans to mosquitoes and from mosquitoes to humans. If any of these is lowered sufficiently, the parasite eventually disappears from that area, as happened in North America, Europe, and parts of the Middle East. However, unless the parasite is eliminated from the whole world, it could re-establish if conditions revert to a combination that favors the parasite's reproduction. Furthermore, the cost per person of eliminating anopheles mosquitoes rises with decreasing population density, making it economically unfeasible in some areas. Prevention of<unk>  may be more cost-effective than treatment of the disease in the long run, but the initial costs required are out of reach of many of the world's poorest people. There is a wide difference in the costs of control (i.e. maintenance of low endemicity) and elimination programs between countries. For example, in China—whose government in 2010 announced a strategy to pursue<unk>  elimination in the Chinese provinces—the required investment is a small proportion of public expenditure on health. In contrast, a similar programme in Tanzania would cost an estimated one-fifth of the public health budget. In areas where<unk>  is common, children under five years old often have anaemia, which is sometimes due to<unk> . Giving children with anaemia in these areas preventive antimalarial medication improves red blood cell levels slightly but does not affect the risk of death or need for hospitalisation. Mosquito control Man spraying kerosene oil in standing water, Panama Canal Zone, 1912 Vector control refers to methods used to decrease<unk>  by reducing the levels of transmission by mosquitoes. For individual protection, the most effective insect repellents are based on DEET or picaridin. However, there is insufficient evidence that mosquito repellents can prevent<unk>  infection. Insecticide-treated nets (ITNs) and indoor residual spraying (IRS) are effective, have been commonly used to prevent<unk> , and their use has contributed significantly to the decrease in<unk>  in the 21st century. ITNs and IRS may not be sufficient to eliminate the disease, as these interventions depend on how many people use nets, how many gaps in insecticide there are (low coverage areas), if people are not protected when outside of the home, and an increase in mosquitoes that are resistant to insecticides. Modifications to people's houses to prevent mosquito exposure may be an important long term prevention measure. Walls where indoor residual spraying of DDT has been applied. The mosquitoes remain on the wall until they fall down dead on the floor. Insecticide-treated nets A mosquito net in use. Mosquito nets help keep mosquitoes away from people and reduce infection rates and transmission of<unk> . Nets are not a perfect barrier and are often treated with an insecticide designed to kill the mosquito before it has time to find a way past the net. Insecticide-treated nets (ITNs) are estimated to be twice as effective as untreated nets and offer greater than 70% protection compared with no net. Between 2000 and 2008, the use of ITNs saved the lives of an estimated 250,000 infants in Sub-Saharan Africa. About 13% of households in Sub-Saharan countries owned ITNs in 2007 and 31% of African households were estimated to own at least one ITN in 2008. In 2000, 1.7 million (1.8%) African children living in areas of the world where<unk>  is common were protected by an ITN. That number increased to 20.3 million (18.5%) African children using ITNs in 2007, leaving 89.6 million children unprotected and to 68% African children using mosquito nets in 2015. Most nets are impregnated with pyrethroids, a class of insecticides with low toxicity. They are most effective when used from dusk to dawn. It is recommended to hang a large "bed net" above the center of a bed and either tuck the edges under the mattress or make sure it is large enough such that it touches the ground. ITNs are beneficial towards pregnancy outcomes in<unk> -endemic regions in Africa but more data is needed in Asia and Latin America. In areas of high<unk>  resistance, piperonyl butoxide (PBO) combined with pyrethroids in mosquito netting is effective in reducing<unk>  infection rates. Questions remain concerning the durability of PBO on nets as the impact on mosquito mortality was not sustained after twenty washes in experimental trials. Indoor residual spraying Indoor residual spraying is the spraying of insecticides on the walls inside a home. After feeding, many mosquitoes rest on a nearby surface while digesting the bloodmeal, so if the walls of houses have been coated with insecticides, the resting mosquitoes can be killed before they can bite another person and transfer the<unk>  parasite. As of 2006, the World Health Organization recommends 12 insecticides in IRS operations, including DDT and the pyrethroids cyfluthrin and deltamethrin. This public health use of small amounts of DDT is permitted under the Stockholm Convention, which prohibits its agricultural use. One problem with all forms of IRS is insecticide resistance. Mosquitoes affected by IRS tend to rest and live indoors, and due to the irritation caused by spraying, their descendants tend to rest and live outdoors, meaning that they are less affected by the IRS. Communities using insecticide treated nets, in addition to indoor residual spraying with 'non-pyrethroid-like' insecticides found associated reductions in<unk> . Additionally, the use of 'pyrethroid-like' insecticides in addition to indoor residual spraying did not result in a detectable additional benefit in communities using insecticide treated nets. Housing modifications Housing is a risk factor for<unk>  and modifying the house as a prevention measure may be a sustainable strategy that does not rely on the effectiveness of insecticides such as pyrethroids. The physical environment inside and outside the home that may improve the density of mosquitoes are considerations. Examples of potential modifications include how close the home is to mosquito breeding sites, drainage and water supply near the home, availability of mosquito resting sites (vegetation around the home), the proximity to live stock and domestic animals, and physical improvements or modifications to the design of the home to prevent mosquitoes from entering. Other mosquito control methods People have tried a number of other methods to reduce mosquito bites and slow the spread of<unk> . Efforts to decrease mosquito larvae by decreasing the availability of open water where they develop, or by adding substances to decrease their development, are effective in some locations. Electronic mosquito repellent devices, which make very high-frequency sounds that are supposed to keep female mosquitoes away, have no supporting evidence of effectiveness. There is a low certainty evidence that fogging may have an effect on<unk>  transmission. Larviciding by hand delivery of chemical or microbial insecticides into water bodies containing low larval distribution may reduce<unk> l transmission. There is insufficient evidence to determine whether larvivorous fish can decrease mosquito density and transmission in the area. Medications There are a number of medications that can help prevent or interrupt<unk>  in travellers to places where infection is common. Many of these medications are also used in treatment. In places where Plasmodium is resistant to one or more medications, three medications—mefloquine, doxycycline, or the combination of atovaquone/proguanil (Malarone)—are frequently used for prevention. Doxycycline and the atovaquone/proguanil are better tolerated while mefloquine is taken once a week. Areas of the world with chloroquine-sensitive<unk>  are uncommon. Antimalarial mass drug administration to an entire population at the same time may reduce the risk of contracting<unk>  in the population, however the effectiveness of mass drug adminisration may vary depending on the prevalence of<unk>  in the area. Other factors such as drug administration plus other protective measures such as mosiquito control, the proportion of people treated in the area, and the risk of reinfection with<unk>  may play a role in the effectiveness of mass drug treatment approaches. The protective effect does not begin immediately, and people visiting areas where<unk>  exists usually start taking the drugs one to two weeks before they arrive, and continue taking them for four weeks after leaving (except for atovaquone/proguanil, which only needs to be started two days before and continued for seven days afterward). The use of preventive drugs is often not practical for those who live in areas where<unk>  exists, and their use is usually given only to pregnant women and short-term visitors. This is due to the cost of the drugs, side effects from long-term use, and the difficulty in obtaining antimalarial drugs outside of wealthy nations. During pregnancy, medication to prevent<unk>  has been found to improve the weight of the baby at
Malaria
Zika fever
Chikungunya
Leptospirosis
Airport malaria
Lassa fever
Brain fever
Dengue fever