Inactivation of human norovirus genogroups I and II and surrogates by free chlorine in postharvest leafy green wash water

Nathan Dunkin, Shih Chi Weng, Joseph G. Jacangelo, Kellogg J. Schwab

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Human noroviruses (hNoVs) are a known public health concern associated with the consumption of leafy green vegetables. While a number of studies have investigated pathogen reduction on the surfaces of leafy greens during the postharvest washing process, there remains a paucity of data on the level of treatment needed to inactivate viruses in the wash water, which is critical for preventing cross-contamination. The objective of this study was to quantify the susceptibility of hNoV genotype I (GI), hNoV GII, murine norovirus (MNV), and bacteriophage MS2 to free chlorine in whole leaf, chopped romaine, and shredded iceberg lettuce industrial leafy green wash waters, each sampled three times over a 4-month period. A suite of kinetic inactivation models was fit to the viral reduction data to aid in quantification of concentration-time (CT) values. Results indicate that 3-log10 infectivity reduction was achieved at CT values of less than 0.2 mg · min/liter for MNV and 2.5 mg · min/liter for MS2 in all wash water types. CT values for 2-log10 molecular reduction of hNoV GI in whole leaf and chopped romaine wash waters were 1.5 and 0.9 mg · min/liter, respectively. For hNoV GII, CT values were 13.0 and 7.5 mg · min/ liter, respectively. In shredded iceberg wash water, 3-log10 molecular reduction was not observed for any virus over the time course of experiments. These findings demonstrate that noroviruses may exhibit genogroup-dependent resistance to free chlorine and emphasize the importance of distinguishing between genogroups in hNoV persistence studies.

Original languageEnglish (US)
Article numbere01457-17
JournalApplied and environmental microbiology
Issue number22
StatePublished - Nov 1 2017


  • Chlorine
  • Disinfection
  • Human norovirus
  • Leafy greens
  • Wash water

ASJC Scopus subject areas

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology


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