Final answer:
The CDC identifies several reasons for outbreaks, such as contaminated food sources, person-to-person transmission, vectors, poor sanitation, and optimal conditions for disease transmission due to environmental and social factors.
Step-by-step explanation:
The Centers for Disease Control and Prevention (CDC) documents several reasons for outbreaks. Among these, some prominent ones include exposure to contaminated food or water sources, the spread of pathogens from person to person, vectors such as mosquitoes or ticks transmitting diseases, poor hygiene and sanitation practices leading to nosocomial or healthcare-associated infections, and the re-emergence of pathogens due to a combination of environmental and social factors.
For example, foodborne illness outbreaks often involve pathogens such as Norovirus, Salmonella, Clostridium perfringens, Campylobacter, and Staphylococcus aureus. These outbreaks can be linked to a common source, such as a contaminated food product. In the case of a Salmonella outbreak traced back to onions from California, the CDC's investigation would confirm the link by finding a genetic match between the Salmonella bacteria from patients and onions, leading to a recall to prevent further spread.