**5.2 Positioning of the One Health concept in relation to human and animal health**

Climate change and environmental change are part of the set of changes that affect ecosystems and promote the emergence and re-emergence of animal diseases. In recent years, more than 70% of these emerging infectious zoonosis have their source in wildlife [Black and Nunn, 2009] and about 60% of emerging infectious diseases are classified as zoonotic, i.e. transmitted from animals to humans [20].

Global warming contributes to the emergence of infectious diseases in the animal and plant world by exerting a marked effect on arthropod insects (mosquitoes, aphids, sandflies, fleas), on ticks that can harbor and transport viruses, bacteria and protozoa. In addition, it causes a thermal increase that increases the risk of extending the current geographical range of these species with the risk of transmission to animals and humans of diseases against which there is no natural immunity [28]. There are a number of meteorological and climatic parameters that can affect human and animal health. In addition to heat, cold, water, ozone, air, allergens and ultraviolet rays, these include heat, cold, water, ozone, air, allergens and ultraviolet rays.

#### *5.2.1 In men*

Some authors argue that climate change is the most significant threat to human health in the 21st century, associated with an increase in chronic diseases, health problems caused by extreme heat and floods, food shortages caused by drought or floods, and various diseases including respiratory problems. The effects of climate change on human health can be both direct and indirect. They are considered direct when they are related to the physiological effects of heat and cold and indirect when they result, for example, from changes in human behavior following forced migration, major natural disasters such as floods and earthquakes, or major outbreaks of food-borne or vector-borne diseases. Not all climate-induced changes are necessarily negative for human health, especially those leading to a decrease in extreme temperatures [42].

#### **a. Impact of heat and cold**

In temperate countries, periods of high heat are sometimes accompanied by relatively high morbidity and mortality. It is estimated, for example, that in Europe, for a one-degree increase in temperature, heat-related mortality would increase by 1–4%. Heat is an immediate health risk to be considered because it has been shown that nearly three-quarters of the hot days observed since 1850 are attributable to climate change [43]. On the other hand, cold can also cause illness and death among the most vulnerable, especially the elderly and homeless. Variations in temperature, especially those that are upwardly oriented, can be the cause of some foodborne and vector-borne zoonotic diseases.

Food-borne bacterial infectious diseases such as salmonellosis and colibacillosis are generally sensitive to temperature and are becoming increasingly important every day even in developed countries such as Europe and the United States.
