<P> Southern Brazil and northern Argentina also experience wetter than normal conditions, but mainly during the spring and early summer . Central Chile receives a mild winter with large rainfall, and the Peruvian - Bolivian Altiplano is sometimes exposed to unusual winter snowfall events . Drier and hotter weather occurs in parts of the Amazon River Basin, Colombia, and Central America . </P> <P> When El Niño conditions last for many months, extensive ocean warming and the reduction in easterly trade winds limits upwelling of cold nutrient - rich deep water, and its economic effect on local fishing for an international market can be serious . </P> <P> More generally, El Niño can affect commodity prices and the macroeconomy of different countries . It can constrain the supply of rain - driven agricultural commodities; reduce agricultural output, construction, and services activities; create food - price and generalised inflation; and may trigger social unrest in commodity - dependent poor countries that primarily rely on imported food . A University of Cambridge Working Paper shows that while Australia, Chile, Indonesia, India, Japan, New Zealand and South Africa face a short - lived fall in economic activity in response to an El Niño shock, other countries may actually benefit from an El Niño weather shock (either directly or indirectly through positive spillovers from major trading partners), for instance, Argentina, Canada, Mexico and the United States . Furthermore, most countries experience short - run inflationary pressures following an El Niño shock, while global energy and non-fuel commodity prices increase . The IMF estimates a significant El Niño can boost the GDP of the United States by about 0.5% (due largely to lower heating bills) and reduce the GDP of Indonesia by about 1.0% . </P> <P> Extreme weather conditions related to the El Niño cycle correlate with changes in the incidence of epidemic diseases . For example, the El Niño cycle is associated with increased risks of some of the diseases transmitted by mosquitoes, such as malaria, dengue, and Rift Valley fever . Cycles of malaria in India, Venezuela, Brazil, and Colombia have now been linked to El Niño . Outbreaks of another mosquito - transmitted disease, Australian encephalitis (Murray Valley encephalitis--MVE), occur in temperate south - east Australia after heavy rainfall and flooding, which are associated with La Niña events . A severe outbreak of Rift Valley fever occurred after extreme rainfall in north - eastern Kenya and southern Somalia during the 1997--98 El Niño . </P>

The term el nino refers to the warming of the central and eastern