Which pathogen accounts for the greatest percentage of foodborne illness in the United States?

• A. Salmonella
• B. E. coli O157:H7
• C. Listeria monocytogenes
• D. Norovirus

Answer: (D)

Norovirus wins out because it is extremely contagious and widespread, leading to the largest number of foodborne illnesses. A tiny number of virus particles can cause infection (low infectious dose), and people can shed the virus before they feel sick and for days after recovery. This means transmission happens easily through contaminated food handled by infected individuals, contaminated surfaces, and even water or shellfish. Because it spreads so efficiently in kitchens, restaurants, schools, and other settings, it generates far more illnesses overall than the other pathogens listed, even though those others can cause severe disease. In short, the sheer ease of spread and the broad opportunities for transmission make Norovirus the leading contributor to foodborne illness in the United States.