Where do new infectious disease from?

Infectious diseases can emerge from a variety of sources, including:

- Animal reservoirs: Many infectious diseases originate in animals, such as viruses, bacteria, or parasites that can be transmitted to humans through contact with infected animals or their bodily fluids. Examples of animal-borne diseases include influenza, HIV/AIDS, Ebola, and rabies.

- Environmental sources: Infectious diseases can also arise from environmental sources, such as soil, water, or plants. For instance, Legionnaires' disease is caused by bacteria that grow in water sources, while tetanus is caused by bacteria found in soil and dust.

- Human-to-human transmission: Some infectious diseases are spread directly from person to person through close contact, such as respiratory droplets, bodily fluids, or sexual contact. Examples include the common cold, influenza, measles, and sexually transmitted infections (STIs).

- Vectors: Infectious diseases can also be transmitted by vectors, which are organisms that carry and transmit pathogens from one host to another. Mosquitoes, ticks, and fleas are common vectors for diseases like malaria, dengue fever, Lyme disease, and plague.

- Laboratory accidents: Rarely, infectious diseases can emerge due to accidental release or escape of pathogens from laboratories where they are being studied or developed for research or vaccine purposes. Examples include the SARS-CoV-2 (coronavirus) and H1N1 influenza pandemic origins that were studied by researchers.