The 21st century has seen a wave of severe infectious disease outbreaks, including the COVID-19 pandemic, which has had a devastating impact on global lives and livelihoods. Recent global changes, such as technological, demographic, and climatic shifts, have increased the risk of infectious disease outbreaks. While improvements in sanitation and healthcare have reduced mortality and morbidity, infectious disease burden remains substantial in low- and middle-income countries, with high mortality and morbidity from neglected tropical diseases, HIV, tuberculosis, and malaria. Emerging and re-emerging infections have persisted throughout the 21st century, indicating a new era of infectious disease defined by rapid spread due to global connectivity and climate change. Recent anthropogenic changes have altered the landscape of infectious disease risk. Climate change affects species range and density, increasing the risk of zoonotic emergence. Demographic changes, such as urbanization and population growth, have created new opportunities for disease emergence. Technological changes, including faster global travel and trade, have enabled rapid pathogen spread. Economic development is a key driver of these changes. Pathogen emergence into human populations has been influenced by global changes, including increased contact with wildlife, habitat destruction, and changes in agricultural practices. The spillover of Nipah virus from bats to pigs was driven by global changes such as pig farming expansion and international trade. Climate change may also play a role in pathogen spillover, as changing environmental conditions can alter species interactions and increase the risk of zoonotic emergence. Local-scale disease dynamics are influenced by demographic factors, including human behavior and immunity. Changes in population density and urbanization have affected the spread of arboviral diseases such as dengue, Zika, and chikungunya. Climate change may also affect the seasonal dynamics of infectious diseases, with some pathogens becoming more seasonal in temperate climates and persisting year-round in tropical locations. Global spread of infectious diseases is influenced by international travel, human migration, and animal and plant trade. Technological changes have reduced the cost of international travel, while demographic changes have increased demand for inexpensive flights. Climate change and urbanization have altered patterns of local mobility and regional migration, while rising demand and technological changes have increased the trade of plants and animals. The emergence of new pathogens and the spread of existing ones are influenced by factors such as climate change, urbanization, and changes in animal and plant trade. The mixing of genetic material of different pathogens within an infected cell can lead to reassortment, which may result in new pathogen variants. The trade of live animals and animal products can also contribute to the spread of infectious diseases, with examples such as African swine fever and Rift Valley fever. In conclusion, the 21st century has seen a new era of infectious disease, characterized by the emergence and spread of pathogens due to global changes. Addressing this challenge requires improving access to healthcare, surveillance, and monitoring in low- and middle-income countriesThe 21st century has seen a wave of severe infectious disease outbreaks, including the COVID-19 pandemic, which has had a devastating impact on global lives and livelihoods. Recent global changes, such as technological, demographic, and climatic shifts, have increased the risk of infectious disease outbreaks. While improvements in sanitation and healthcare have reduced mortality and morbidity, infectious disease burden remains substantial in low- and middle-income countries, with high mortality and morbidity from neglected tropical diseases, HIV, tuberculosis, and malaria. Emerging and re-emerging infections have persisted throughout the 21st century, indicating a new era of infectious disease defined by rapid spread due to global connectivity and climate change. Recent anthropogenic changes have altered the landscape of infectious disease risk. Climate change affects species range and density, increasing the risk of zoonotic emergence. Demographic changes, such as urbanization and population growth, have created new opportunities for disease emergence. Technological changes, including faster global travel and trade, have enabled rapid pathogen spread. Economic development is a key driver of these changes. Pathogen emergence into human populations has been influenced by global changes, including increased contact with wildlife, habitat destruction, and changes in agricultural practices. The spillover of Nipah virus from bats to pigs was driven by global changes such as pig farming expansion and international trade. Climate change may also play a role in pathogen spillover, as changing environmental conditions can alter species interactions and increase the risk of zoonotic emergence. Local-scale disease dynamics are influenced by demographic factors, including human behavior and immunity. Changes in population density and urbanization have affected the spread of arboviral diseases such as dengue, Zika, and chikungunya. Climate change may also affect the seasonal dynamics of infectious diseases, with some pathogens becoming more seasonal in temperate climates and persisting year-round in tropical locations. Global spread of infectious diseases is influenced by international travel, human migration, and animal and plant trade. Technological changes have reduced the cost of international travel, while demographic changes have increased demand for inexpensive flights. Climate change and urbanization have altered patterns of local mobility and regional migration, while rising demand and technological changes have increased the trade of plants and animals. The emergence of new pathogens and the spread of existing ones are influenced by factors such as climate change, urbanization, and changes in animal and plant trade. The mixing of genetic material of different pathogens within an infected cell can lead to reassortment, which may result in new pathogen variants. The trade of live animals and animal products can also contribute to the spread of infectious diseases, with examples such as African swine fever and Rift Valley fever. In conclusion, the 21st century has seen a new era of infectious disease, characterized by the emergence and spread of pathogens due to global changes. Addressing this challenge requires improving access to healthcare, surveillance, and monitoring in low- and middle-income countries