Which of the following is an example of a biological infectious hazard?

The correct choice demonstrates a clear connection to biological infectious hazards, which refer to organisms such as bacteria, viruses, fungi, and parasites that can cause disease. Contact with infected patients exemplifies this as it involves direct or indirect exposure to pathogens that can be transmitted through bodily fluids, respiratory droplets, or skin contact. This type of hazard is particularly relevant in healthcare settings where the risk of infection can significantly impact both healthcare workers and patients. Understanding this concept is critical for maintaining safe practices and preventing the spread of infectious diseases in clinical environments.

Other options represent different types of hazards. Chemical spillage pertains to the risks associated with hazardous substances, while exposure to dangerous machinery involves mechanical hazards. Psycho-social stress relates to mental health and workplace dynamics, further distinguishing these options from the biological infectious hazard defined in the question.