Defining Transmission Routes for Vibrio Infections

Purpose

This page explains the categories and characteristics used to define transmission routes for Vibrio infections. It can be helpful in interpreting and understanding the "routes of transmission" section in the annual summaries of Vibrio data.

Overview

The Cholera and Other Vibrio Illness Surveillance annual summaries provide information on the possible and confirmed sources of Vibrio infections.

Transmission routes are classified based on exposures and the specimens from which the Vibrio bacteria was isolated.

Steps to determine transmission route

  • Exposures
    Identifying the things a patient consumed or had contact with
  • Specimen sites
    Identifying the source of the specimen(s) from which Vibrio bacteria were isolated
  • Transmission routes
    Classifying a case into one of five categories based on exposure and specimen site information

Exposure categories

To classify transmission routes, the first step is to categorize patient exposures.

For a given illness episode, more than one patient exposure can be reported to COVIS; each reported exposure is categorized individually. If all exposures fall into a single category, then the case is considered to have a single exposure category. If not, the case is considered to have multiple exposure categories.

For a given case, if any exposure is reported, we assume that other exposures for which information was not reported were not present.

Exposures are classified using three categories:

Seafood consumption

Ingestion of any type of seafood. Does not include touching seafood.

Marine/estuarine contact

Includes direct skin contact with marine/estuarine life, bodies of water, or drippings from raw or live seafood.

Unknown or no exposure

All seafood consumption or marine/estuarine exposure history questions are reported as unknown, or no exposures are reported.

Specimen site categories

The next step in classifying transmission routes is to categorize reported specimen sites.

For a given illness episode, more than one specimen site can be reported; each reported site is categorized individually.

If all specimen sites fall into a single category, then the report is considered to have a single specimen site category. If not, then the report is considered to have multiple specimen site categories.

Specimen sites are classified using five categories:

Gastrointestinal site (GI)

Stool, bile, appendix, rectum, gall bladder, colon

Blood or other normally sterile site (sterile)

Blood, cerebrospinal fluid (CSF), peritoneal fluid, lumbar disc fluid, lymph node, bullae

Skin or soft tissue site (SST)

Wound, ear (other than otitis media and middle ear, which are included in 'other, non-sterile site'), appendage, tissue

Other, non-sterile site (ONS)

Urine, sputum, aspirate, bronchial washing, effusion, catheter, endotracheal, eye, nasal, placenta, respiratory, sinus, tonsil

Unknown site (unknown)

No specimen site reported or no site specified for 'other'

Note: The lists of sites for each category above are not intended to be exhaustive. Rather, they reflect the sites traditionally reported to COVIS and may be updated if new sites are reported.

Transmission route

The final step in classifying transmission involves review of exposure and specimen site categories for each reported case.

Cases are classified into one of five transmission routes (foodborne, likely foodborne, non-foodborne, likely non-foodborne, and unknown) based on the criteria below:

Single exposure category: seafood consumption

  • Foodborne: Vibrio isolated only from GI or sterile site OR Vibrio isolated from multiple specimen site categories, with GI reported.
  • Likely foodborne: Vibrio isolated only from SST, ONS, or unknown sites OR Vibrio isolated from multiple specimen site categories, not including GI.

Single exposure category: marine/estuarine contact

  • Non-foodborne: Vibrio isolated only from SST or sterile site OR Vibrio isolated from multiple specimen site categories, with SST reported.
  • Likely non-foodborne: Vibrio isolated only from GI, ONS, or unknown sites OR Vibrio isolated from multiple specimen site categories, not including SST.

Multiple exposure categories: both seafood consumption AND marine/estuarine contact

  • Foodborne: Vibrio isolated only from a GI site OR Vibrio isolated from multiple specimen site categories, with GI reported and SST not reported.
  • Non-foodborne: Vibrio isolated only from a SST site OR Vibrio isolated from multiple specimen site categories, with SST reported and GI not reported.
  • Unknown: Vibrio isolated only from a sterile, ONS, or unknown site OR Vibrio isolated from multiple specimen site categories, including either 1) both GI and SST or 2) neither GI nor SST.

Unknown or no reported exposure

  • Foodborne: Vibrio isolated only from a GI site OR Vibrio isolated from multiple specimen site categories, with GI reported and SST not reported.
  • Non-foodborne: Vibrio isolated only from a SST site OR Vibrio isolated from multiple specimen site categories, with SST reported and GI not reported.
  • Unknown: Vibrio isolated only from a sterile, ONS, or unknown site OR Vibrio isolated from multiple specimen site categories, including either 1) both GI and SST or 2) neither GI nor SST.

Note: Categorization is the same for "multiple exposure categories" and "unknown or no reported exposure."

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Content Source:
National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)