Shellfish tend to be contaminated with human viruses from what source?

• A. Human fecal waste
• B. Industrial waste
• C. Plant runoff
• D. Airborne dust

Answer: (A)

Shellfish accumulate human viruses from water contaminated with human fecal waste because they are filter feeders, which continuously strain large volumes of water and concentrate any microorganisms present. When sewage or wastewater containing viruses shed in human feces enters a growing area, viruses such as norovirus and hepatitis A can persist in the water and become concentrated in the tissues of oysters, clams, and mussels. Consuming these shellfish, especially raw or undercooked, can then transmit illness to people.

Industrial waste can carry chemicals and some contaminants but is not a primary source of human enteric viruses in shellfish. Plant runoff primarily brings nutrients and plant pathogens, not human viruses in the amounts that contaminate shellfish, and airborne dust is not the main mechanism by which shellfish become heavily contaminated.