detection of a potential human outbreak. horses severe disease may also occur in horses. several vaccines for these animals are now available. before the availability of veterinary vaccines, around 40% of horses infected in north america died. epidemiology according to the center for disease control, infection with west nile virus is seasonal in temperate zones. climates that are temperate, such as those in the united states and europe, see peak season from july to october. peak season changes depending on geographic region and warmer and humid climates can see longer peak seasons. all ages are equally likely to be infected but there is a higher amount of death and neuroinvasive west nile virus in people 60–89 years old. people of older age are more likely to have adverse effects. there are several modes of transmission, but the most common cause of infection in humans is by being bitten by an infected mosquito. other modes of transmission include blood transfusion, organ transplantation, breast-feeding, transplacental transmission, and laboratory acquisition. these alternative modes of transmission are extremely rare. prevention prevention efforts against wnv mainly focus on preventing human contact with and being bitten by infected mosquitoes. this is twofold, first by personal protective actions and second by mosquito-control actions. when a person is in an area that has wnv, it is important to avoid outdoor activity, and if they go outside they should use a mosquito repellent with deet. a person can also wear clothing that covers more skin, such as long sleeves and pants. mosquito control can be done at the community level and include surveillance programs and control programs including pesticides and reducing mosquito habitats. this includes draining standing water. surveillance systems in birds is particularly useful. if dead birds are found in a neighborhood, the event should be reported to local authorities. this may help health departments do surveillance and determine if the birds are infected with west nile virus. despite the commercial availability of four veterinary vaccines for horses, no human vaccine has progressed beyond phase ii clinical trials. efforts have been made to produce a vaccine for human use and several candidates have been produced but none are licensed to use. the best method to reduce the risk of infections is avoiding mosquito bites. this may be done by eliminating standing pools of water, such as in old tires, buckets, gutters, and swimming pools. mosquito repellent, window screens, mosquito nets, and avoiding areas where mosquitoes occur may also be useful. climate change global distribution of west nile virus from the cdcfurther information: climate change and infectious diseases like other tropical diseases which are expected to have increased spread due to climate change, there is concern that changing weather conditions will increase west nile virus spread. climate change will affect disease rates, ranges, seasonality and affects the distribution of west nile virus. projected changes in flood frequency and severity can bring new challenges in flood risk management, allowing for increased mosquito populations in urban areas. weather conditions affected by climate change including temperature, precipitation and wind may affect the survival and reproduction rates of mosquitoes, suitable habitats, distribution, and abundance. ambient temperatures drive mosquito replication rates and transmission of wnv by affecting the peak season of mosquitoes and geographic variations. for example, increased temperatures can affect the rate of virus replication, speed up the virus evolution rate, and viral transmission efficiency. furthermore, higher winter temperatures and warmer spring may lead to larger summer mosquito populations, increasing the risk for wnv. similarly, rainfall may also drive mosquito replication rates and affect the seasonality and geographic variations of the virus. studies show an association between heavy precipitation and higher incidence of reported wnv. likewise, wind is another environmental factor that serves as a dispersal mechanism for mosquitoes. mosquitoes have extremely wide environmental tolerances and a nearly ubiquitous geographical distribution, being present on all major land masses except antarctica and iceland. nevertheless, changes in climate and land use on ecological timescales can variously expand or fragment their distribution patterns, raising consequent concerns for human health.