Which of the following groups of microorganisms are associated with sewage backflow?

The association of bacteria, parasites, and viruses with sewage backflow is rooted in the understanding of pathogens that are commonly found in contaminated water. Sewage typically contains a diverse array of microorganisms, many of which can pose health risks to humans.

Bacteria are abundant in sewage and can include various harmful species such as Escherichia coli, Salmonella, and Shigella, which can cause severe gastrointestinal illnesses if ingested. Parasites, such as Giardia and Cryptosporidium, are also common in sewage and can lead to infections through contaminated water or surfaces. Additionally, viruses like norovirus and hepatitis A can thrive in wastewater, spreading infections easily in environments impacted by sewage backflow.

In contrast, while yeasts and molds (as mentioned in the first option) can be found in various environments, they are not typically considered primary pathogens associated with sewage. Fungi and algae (from the third option) might be present in polluted water but do not primarily relate to the immediate health threats of sewage backflow. Lastly, the mention of spores and insects in another choice does not accurately reflect the major concerns regarding health risks linked to sewage contamination. Hence, the chosen answer accurately captures the main groups of pathogens that are relevant in the context of sewage