Climate change accelerates the spread of disease primarily because global warming causes extreme weather and melts glaciers and causes sea level rises. Global warming temperatures enlarge the geographic range in which disease-carrying animals, insects and microorganisms--as well as the germs and viruses they carry--can survive.
For example, mosquitoes carrying dengue fever. using dwell at elevations no higher than 3,300 feet, but because of warmer temperatures they have recently been detected at 7,200 feet in Colombia’s Andes Mountains. According to biologist, malaria-carrying mosquitoes at higher-than-usual elevations in Indonesia in just the last few years. These changes happen not because of the kinds of extreme heat we’ve experienced in recent months, but occur even with minuscule increases in average temperature.
How mosquitoes carrying dengue fever to human body
Bird flu disease is an another example that is likely to spread more quickly as the Earth warms up. But for a different reason: A United Nations study found that global warming is contributing to an increased loss of wetlands around the world. This trend is already forcing disease-carrying migrating birds, who ordinarily seek out wetlands as stopping points, to instead land on animal farms where they mingle with domestic poultry, risking the spread of the disease via animal-to-human and human-to-human contact.
All the news is not good for less developed parts of the world either. According to scientist research,they have found that more than two-thirds of waterborne disease outbreaks (such as cholera) follow major precipitation events, which are already increasing due to global warming.