Climate change refers to long-term variations in temperature and weather patterns. These can be natural variations, due for example to those of the solar cycle or to massive volcanic eruptions. However, since the 1800s, human activities have been the main cause of these changes, mainly due to the burning of fossil fuels such as coal, oil and gas. The emissions that cause climate change come from all regions of the planet and affect everyone, but some countries produce more than others. The emergence of a disease has multiple factors, which are associated with environmental, social and demographic changes, and changes to health policies and systems, among others. The same factors can lead to the re-emergence of endemic diseases. Climate and climate change can have direct effects on the emergence and re-emergence of infectious diseases by influencing pathogen survival, arthropod vector survival and reproduction, and reservoir host abundance.