Salmonellosis

• Reporting criteria
• The disease and its epidemiology
• Case definition

• Laboratory testing
• Case investigation
• Disease control measures

• References
• Contact

What and how to report to the Colorado Department of Public Health and Environment (CDPHE) or local public health agency  

• All specimens with a positive test for Salmonella (regardless of specimen source) by culture, polymerase chain reaction (PCR), or other form of testing should be reported to public health within four (4) days of the positive test result.
  • All positive Salmonella laboratory tests should be reported to public health, regardless of symptoms. Public health will make the determination of whether the case meets the case definition.
• Cases should be reported using EpiTrax Reportal, fax, or telephone to CDPHE or local health departments (telephone and fax numbers are listed at the end of this document).
• All potential foodborne, waterborne, and enteric disease outbreaks should be reported immediately to CDPHE or local health departments and entered into EpiTrax, even if the causative agent is not yet known.
  • In general, an “outbreak” is defined as an increase in the number of illnesses above what is normally expected among a specific population, within a given area, over a certain period of time.
  • Specifically, a foodborne disease outbreak occurs when two or more people get the same illness from the same contaminated food or drink.

Purpose of surveillance and reporting

• To identify cases for investigation and potential outbreaks
• To monitor trends in disease incidence

Back to top

Etiologic agent

Salmonellosis refers to the disease caused by any serotype of bacteria in the genus Salmonella other than Salmonella Typhi (the Salmonella serotype that causes typhoid fever), Salmonella Paratyphi A, S. Paratyphi B (tartrate-negative), or S. Paratyphi C. Approximately 2,500 different serotypes of Salmonella have been identified.

Clinical description

The most common symptoms of salmonellosis are diarrhea (that can be bloody), stomach cramps, and fever. Some people may also experience nausea, vomiting, and headache. Dehydration may be severe, especially among infants and the elderly, and invasive disease may occur. Most people recover within 4 to 7 days.

The infection may also present as septicemia, a urinary tract infection, an abscess, arthritis, or cholecystitis (inflammation of the gallbladder). Gastrointestinal symptoms may be absent in these instances. Asymptomatic infections may occur.

Reservoirs

Salmonella bacteria are widely distributed in the animal kingdom, including livestock, pets, poultry and other birds, reptiles, and amphibians. Most infected animals are chronic carriers and may not have symptoms. Humans can also be sources of infection.

Modes of transmission

Salmonella bacteria are transmitted via the fecal-oral route. The most common mode of transmission is ingestion of food or water that has been contaminated with human or animal feces. This includes raw or undercooked poultry, eggs and egg products, undercooked meats, produce, and raw milk or milk products. However, any food contaminated with the bacteria can be a source of infection, and outbreaks have involved a wide variety of foods, such as peanut butter, snack foods, frozen shrimp, and pre-packaged salad. In addition, pet chickens and reptiles such as snakes and lizards (including iguanas and bearded dragons) are chronic carriers of these bacteria and are relatively common sources of infection. Person-to-person spread can occur, especially among household contacts, children in childcare, the elderly and developmentally disabled living in residential facilities, and through certain types of sexual contact (e.g., oral-anal contact). The infectious dose is thought to vary depending on the serotype, the vehicle with which Salmonella is ingested, and host factors such as age and the presence of certain medical conditions. The risk of transmission may be elevated during international travel, especially to regions where the bacteria is endemic.

Incubation period

The average incubation period is about 12 to 36 hours but can range from 6 hours to 6 days. During outbreaks, incubation periods of more than 10 days have been observed.

Infectious period

The disease is communicable for as long as the infected person excretes Salmonella bacteria in their stool, which generally begins at the onset of symptoms and may last days to months and, in rare situations, a year or more depending on serotype. As is the case with most enteric illnesses, persons are most infectious when they have diarrhea and are usually more infectious than those who are asymptomatic. Treatment with antibiotics may prolong carriage.

Epidemiology

Salmonellosis is reported throughout the year in Colorado, with reported cases peaking in the summer months. During 2023, 916 cases were reported in Colorado, with a five-year average of 824 cases per year (2019-2023). The three most commonly reported serotypes are S. Typhimurium, S. Enteritidis, and S. Newport.

In 2022, 56,129 salmonellosis cases (excluding S. Typhi and S. Paratyphi) were reported in the United States, with a five-year average of 54,038 cases per year (2018-2022). During this time period, 28% of salmonellosis cases in the FoodNet catchment area were hospitalized and < 1% of cases died. Eight percent of cases were outbreak-associated, and approximately 9% were acquired internationally.

Recent multistate salmonellosis outbreaks have been attributed to a wide range of sources, including cantaloupe, cucumbers, charcuterie meats, dry dog food, eggs, backyard poultry, pet bearded dragons and small turtles, among others.

For more data, see Colorado reportable disease data (Colorado data), CDC WONDER and CDC BEAM Dashboard (national data), and CDC FoodNet Fast (FoodNet catchment area data).

Back to top

Clinical criteria

An illness of variable severity commonly manifested by diarrhea, abdominal pain, nausea, and sometimes vomiting. Asymptomatic infections may occur, and the organism may cause extra-intestinal infections.

Laboratory criteria for diagnosis

Confirmatory laboratory evidence:

• Isolation of Salmonella spp. from a clinical specimen

Supportive laboratory evidence:

• Detection of Salmonella spp. in a clinical specimen using a culture-independent diagnostic test (CIDT) 

Epidemiologic linkage

A clinically compatible case that is epidemiologically linked to a case that meets the supportive or confirmatory laboratory criteria for diagnosis.

Criteria to distinguish a new case from an existing case

A case should not be counted as a new case if laboratory results were reported within 365 days of a

previously reported infection in the same individual. When two or more different serotypes are identified from one or more specimens from the same individual, each should be reported as a separate case.

Case classification

Confirmed

• A case that meets the confirmed laboratory criteria for diagnosis.

Probable

• A case that meets the supportive laboratory criteria for diagnosis

OR 

• A clinically compatible case that is epidemiologically linked to a case that meets the supportive or confirmatory laboratory criteria for diagnosis.

Note: Epi-linked probable cases can be epi-linked to either a confirmed or probable case, as long as the index case has a positive test result (see laboratory criteria, above). If multiple serotypes of Salmonella are identified from one or more specimens from the same person, each should be reported as a separate case (even if reported within 365 days). Additionally, confirmed or laboratory-confirmed probable cases can include asymptomatic infections and infections at sites other than the gastrointestinal tract that are laboratory-confirmed (rare).

Back to top

• The Colorado State Public Health Laboratory (“State Lab”) provides testing services to support public health investigations.
• The State Lab may test clinical and/or environmental samples when determined to be necessary for public health investigations. These services vary by pathogen but may include:
  • Testing for individuals who have been restricted or excluded from work or child care by public health
  • Testing for outbreak investigations, with prior approval from CDPHE
  • Other testing services as discussed with CDPHE
• The State Lab maintains a test directory, guidance for submitting samples, and other helpful resources on their webpage.
  • Additional questions can be directed to the Lab Coordinators by email (cdphe_labcoordinators@state.co.us; preferred method) or phone 303-692-3069.
• Clinical and commercial laboratories are required to submit Salmonella isolates or clinical material to the State Lab for confirmation and whole genome sequencing (WGS; i.e., molecular subtyping). While these submissions do not require prior approval from CDPHE, a complete lab requisition form is required for each isolate/clinical material submission to the State Lab.
  • WGS results are used for public health surveillance only and cannot be released to clinical providers or used for clinical decision-making.
  • The State Lab does not perform routine antimicrobial susceptibility testing (AST); providers interested in AST should order it from a clinical or commercial laboratory.

Back to top

Interview all confirmed and probable (including epi-linked probable) cases of salmonellosis to determine:

• Potential source of infection, and implement disease control measures as appropriate
• If others are ill (i.e., could this be an outbreak?)
• If the case may be a source of infection for others (e.g., a high-risk worker or a diapered child); and if so, prevent further transmission

Local health departments have primary responsibility for interviews of sporadic cases in their jurisdictions. CDPHE is available to assist with case investigations upon request through CDPHE’s Enteric Disease Interview Team (EDIT). Interviews should be conducted and appropriate disease control measures implemented as soon as reasonably possible after the case is reported. Interviews should not be delayed until confirmatory laboratory testing is completed at the State Lab.

Forms 

For single cases, use the CDPHE Salmonellosis case investigation form for your interview, and enter the information into the case’s morbidity record (CMR) in EpiTrax. Interview all cases, regardless of specimen source (stool, blood, wound, urine, etc.).

For surveillance purposes, collect exposure histories for the seven days before symptom onset. Determining the exposure period can be difficult for cases who do not have an acute onset of gastrointestinal symptoms. It’s important to do a complete assessment for GI illness, even when the specimen was collected from a source other than stool, to determine if any GI symptoms were present, even if mild. Use the following criteria to determine the case’s exposure period:

1. If the case reports diarrhea or vomiting, then use the onset date of diarrhea/vomiting to determine exposure period.
2. If the case does not report diarrhea or vomiting but reports other clinically relevant symptoms (see Clinical description section above), then use the onset date of other symptoms to determine exposure period.
3. If the case does not report onset of any clinically relevant symptoms (see Clinical description section above), then use the specimen collection date to determine exposure period.*

*Do not enter specimen collection date as “onset date” in EpiTrax (clinical tab); use this date to determine exposure period only. “Onset date” in EpiTrax only applies if the case experienced symptoms of illness. Otherwise, leave this field blank.

After completing the case interview, enter the information into the case’s morbidity record (CMR) in EpiTrax, including the investigation form, and conduct any necessary disease control activities. If an outbreak is suspected, create a new outbreak in EpiTrax and contact CDPHE if assistance is needed; this includes requests for additional testing at the State Lab.

Identify and evaluate contacts

Symptomatic contacts

• Contacts of a case with a positive lab test who have clinically compatible symptoms are epi-linked probable cases and are treated the same as cases with a positive lab test for disease control purposes. See Disease control measures below.
  • Complete a case interview with all epidemiologically linked probable cases.
  • Epi-linked probable cases who have been interviewed should be entered into EpiTrax as a new, probable salmonellosis morbidity record (CMR). Link this newly created CMR to the laboratory-confirmed case’s CMR under the “contacts” tab in EpiTrax.
• Refer symptomatic individuals who have not previously been tested (especially if they are high-risk workers) to their health care provider for stool testing and appropriate medical care.
• If a common source of exposure is suspected (e.g. a shared meal or social event), create an outbreak record in EpiTrax and notify CDPHE as soon as possible.   

Asymptomatic contacts 

• Ask about high-risk occupations, including food handling, health care, community residential programs, and child care/ school attendance.
• Provide information on symptom monitoring and next steps if symptoms develop.
  • Stress the importance of good hand washing, personal hygiene, excluding themselves from work, and notifying their supervisor whenever they have a diarrheal illness.
  • If an asymptomatic contact develops diarrhea, follow the steps outlined above under Symptomatic contacts. If the contact works in a high-risk setting, exclude them from work per the Managing special situations section below, even in the absence of a positive lab test.

Reported incidence is higher than usual/outbreak suspected

If the number of reported cases of salmonellosis in your jurisdiction is higher than usual, or if an outbreak is suspected, investigate the situation to determine the source of infection and mode of transmission. Notify CDPHE as soon as possible to discuss potential stool testing of untested, symptomatic contacts and enter the outbreak into EpiTrax. CDPHE staff can assist local public health agencies to investigate outbreaks and determine disease control recommendations to prevent further cases, as well as coordinate surveillance of cases that cross county lines.

Back to top

Salmonella (salmonellosis) | CDC

Treatment

Antibiotics are not usually indicated for uncomplicated salmonellosis cases. Antibiotics do not shorten the duration of disease and may prolong shedding of the bacteria in the stool. However, antibiotics may be prescribed for cases with gastroenteritis and an increased risk of invasive disease, such as:

• Infants < 3 months of age
• Cases with:
  • Chronic gastrointestinal tract disease
  • Malignant neoplasms
  • HIV infection
  • Immunosuppressive illnesses and therapies
  • Severe colitis

In general, individuals experiencing diarrhea are at risk of dehydration due to loss of fluids. If symptoms persist, worsen, or are severe, cases should promptly seek medical care.

Prophylaxis

No prophylactic treatment of close contacts is recommended.

Education

Encourage the case to:

• Avoid preparing food for other individuals until diarrhea has resolved.
• Always wash hands thoroughly with soap and water for at least 20 seconds before eating or preparing food, after using the toilet, after changing diapers, and after touching pets or other animals (especially reptiles).
• After changing diapers, wash your hands and the child’s hands for at least 20 seconds. Clean and sanitize diaper changing stations/areas often.
  • In child care and other institutional settings, dispose of stool and soiled diapers/linens in a sanitary manner.
• Thoroughly cook all food products from animals, especially poultry and eggs, and avoid consuming raw or cracked eggs, unpasteurized milk, or other unpasteurized products.
• Keep food that will be eaten raw, such as fruits and vegetables, separate from raw, animal-derived food products (e.g., raw meat, fish, poultry) by cleaning or using different knives and cutting boards during preparation. Store raw, animal-derived foods away from other foods that will be eaten raw while in the refrigerator.
• Infants, children, elderly, and immunocompromised individuals should avoid contact with reptiles and reptiles’ cages.

Managing special situations

Food handlers 

• Food handlers with salmonellosis must be excluded from work until at least 24 hours after diarrhea has resolved without the use of anti-diarrheal medications and adequate hygiene can be maintained, ideally as verified by environmental health. "Exclude" means to prevent a person from working as an employee in a food establishment or entering a food establishment as an employee.
  • While individual circumstances may vary, cases are generally not required to provide two consecutive negative stool tests to return to work.
  • If a case has questionable hygienic practices or there are other concerns, consider excluding the case from work until the case has obtained two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given.
• In an outbreak situation, longer exclusion and/or return to work testing may be required to return to food handling.
• The Colorado Retail Food Establishment Regulations may require additional restrictions or disease control measures for the case, their close contacts, and/or their employer.
  • Please consult with environmental health to determine if the case’s place of employment should enact additional disease control measures to be in compliance with the regulations.

Child care centers/preschools

Refer child care providers to the CDPHE Infectious Disease in Child Care and School Settings for an overview of Salmonella infections.

• Children or staff with salmonellosis should be excluded until at least 24 hours after diarrhea has resolved without the use of anti-diarrheal medications.
  • Parents of cases should be counseled not to take their children to another child care center during this period of exclusion in order to avoid possible transmission of salmonellosis at a new location.
  • Since many child care center staff assist with food preparation and/or feeding children, it is very important that staff with Salmonella infection follow this guidance. See Disease control measures section (Food handlers) above.
  • If there are concerns about hygienic practices at the child care center, consider excluding the case from care until the case has obtained two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given.
• Determine whether additional children or staff are (or have recently been) ill with diarrheal illness.
  • Other children or staff with diarrhea should be excluded and referred to their health care provider for stool testing and appropriate medical care.
  • If other cases in the center are identified, initiate an outbreak investigation and consider sending a letter home to parents.
    • In an outbreak situation, longer exclusion and/or return to work/child care testing may be required. Contact CDPHE for assistance.
  • If the case is the only person in the classroom or facility who has been ill, no further action is indicated for other children/staff in that classroom or center.
• Reinforce the importance of meticulous hand washing, proper sanitizing and disinfection, and proper diaper changing technique with child care center staff. If possible, this should be verified by environmental health.
• Consult with CDPHE for instances in which children attend drop in style care at gyms, churches, etc.

Schools 

Refer school personnel to the CDPHE Infectious Disease in Child Care and School Settings for an overview of Salmonella infections. 

• Students or staff with salmonellosis should be excluded until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications.
  • If there are concerns about the case’s hygiene (e.g., the case has developmental disabilities and wears diapers) consider obtaining two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given before a case returns to school.
• Students or staff who handle food for others must not prepare food until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications. See Disease control measures section (Food handlers) above.
• In an outbreak situation, longer exclusion and/or return to work testing may be required.

Community residential programs (including facilities serving the developmentally disabled)

Actions taken in response to a case of salmonellosis in a community residential program will depend on the type of program and the level of functioning of the residents. In general: 

• Staff members with salmonellosis should be excluded from work until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications.
  • For staff members who provide direct patient care (e.g., feed patients, give mouth or denture care, or give medications), follow guidelines for staff in health care facilities below.
  • While individual circumstances may vary, in general, staff members are not required to provide two negative stool tests to return to work.
• Residents with salmonellosis should be placed on contact precautions until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications.
  • If the resident has questionable hygiene, is incontinent, or there are other concerns, the resident should remain on contact precautions until they have obtained two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given.
• Residents and staff with salmonellosis must be excluded from handling or preparing food for others until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications. See Disease control measures (Food handlers) above.
• In an outbreak situation, longer exclusion and/or return to work testing may be required.

Patients and staff in health care facilities (including hospitals, medical and dental clinics, skilled nursing and long-term care facilities) 

Hospitals and skilled nursing/long-term care facilities generally have written infection control policies and procedures for handling cases of communicable disease among patients and staff members. 

If a health care facility does not have such policies in place, provide the following recommendations: 

• Health care workers with salmonellosis who provide direct patient care or handle medications (e.g., pharmacists) should be excluded from work until at least 24 hours after diarrhea has resolved without the use of anti-diarrheal medications.
  • While individual circumstances may vary, in general, health care workers are not required to provide two negative stools samples to return to work.
• Patients with salmonellosis should be placed on contact precautions until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications.
  • If the patient has questionable hygiene, is incontinent, or there are other concerns, the patient should remain on contact precautions until they have obtained two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given.
• In an outbreak situation, longer exclusion and/or return to work testing may be required.

Environmental measures

• Implicated food items and food prepared by cases must be removed from the environment.
• A decision about testing suspect/implicated food items must be made in consultation with CDPHE.
  • The general policy of the State Lab and the Communicable Disease Branch is only to test food samples associated with outbreaks, not in single cases.
• If a commercial product is suspected, CDPHE Communicable Disease Branch will coordinate follow-up with the CDPHE Division of Environmental Health and Sustainability and relevant outside agencies.

Back to top

American Academy of Pediatrics. Red Book: 2024-2027 Report of the Committee on Infectious Diseases, 33rd Edition. Illinois, Academy of Pediatrics, 2024.  

CDC website (click on “Diseases and Conditions”) 

Centers for Disease Control and Prevention (CDC). FoodNet Fast: Pathogen Surveillance Tool. Atlanta, Georgia: U.S. Department of Health and Human Services. Available from URL: http://wwwn.cdc.gov/foodnetfast. Accessed 05/16/2025.

Heymann DL, ed. Control of Communicable Diseases Manual, 21st Edition. Washington, DC, American Public Health Association, 2022.

National Notifiable Diseases Surveillance System. Annual Summary Data 2018-2022 Request. (n.d.). https://wonder.cdc.gov/nndss-annual-summary.html

Salmonellosis (Salmonella spp.) 2017 Case Definition | CDC. (n.d.). https://ndc.services.cdc.gov/case-definitions/salmonellosis-2017/

Back to top

CDPHE Communicable Disease Branch

• Phone: 303-692-2700 or 800-866-2759
• Fax: 303-782-0338
• After hours: 303-370-9395

CDPHE Lab Coordinators: 

• Email (preferred): cdphe_labcoordinators@state.co.us  
• Phone: 303-692-3069

Back to top