Shigellosis ◊

 

Literature Recommendations

Exclusion-Case in SOS*
(Symptomatic)

Yes ◊ [1,2,3,4,5,6,8,10,11,12,14, 21]
Grade III-A

Exclusion-Case in SOS*
(Asymptomatic or previously symptomatic but now recovered)

Yes ◊ (Disagreement exists.[5,11,14] Code requires this, but literature does not support)
Clearance required in SOS* [8b]
Exclusion in Special Cases [4a]
Grade III-C

Clearance-Case in SOS*

Yes- 2 negative stools cultures, 24 hours apart and at least 48 hours post antibiotics. [1,3,4,8,12,14,15,21]
Grade III-A

Exclusion of Contact
(Symptomatic)

Yes ◊ [1,2,3,4,5,6,8,10,11,12,14,21]
Grade III-A

Exclusion of Contact
(Asymptomatic)

No [5,11,14]
Clearance required in SOS* [8b]
Exclusion in Special Cases [4a]
Grade III-C

Exclusion-Case in Children
(Group setting with children ≤ 5 years of age)
(Symptomatic)

Yes [1,2,3,5,8,12,13,14,15, 20]
Grade II-A

Exclusion-Case in Children
(Group setting with children ≤ 5 years of age)
(Asymptomatic or previously symptomatic but now recovered)

Yes [5,14,22]
Cohort asymptomatic persons [20]
Grade II-C

◊ Applicable Code

CCR 2613
* SOS (Sensitive Occupations or Situations) is not defined precisely in either the Code of Regulations or Health & Safety Code. See Attachment 2 for the definition of food workers.
◊ See California Code of Regulations, Attachment 1, for details.
+ Local health departments may elect to follow more restrictive exclusion and clearance criteria

a See number four under the Preventive Measures Exclusions
b See number seven under the Preventive Measures Exclusions

Disease Trends in the U.S.:

According to the Surveillance for Foodborne-Disease Outbreaks in the United States these are the trends seen from 1982-2002. It should be kept in mind that these are only a small fraction of the cases that are reported to Center for Disease Control and Prevention (CDC) through passive surveillance systems. If one were to take into account 1) asymptomatic cases, 2) symptomatic cases that do not seek medical care, 3) diarrheal illnesses that are treated without stool confirmation and 4) not all positive laboratory results are reported to public health officials, the estimated cases of Shigellosis per year would be much higher.

  • In 1983, 14,898 cases of foodborne diseases linking to 505 outbreaks were reported to CDC. A large outbreak of Shigella dysenteriae type 2 infections occurred among persons who ate at a Maryland hospital cafeteria; 1,502 persons were ill, and 24 were hospitalized. Illness was associated with consumption of raw vegetables at a cafeteria salad bar. [16] 
  • In 1986, 12,781 cases of foodborne diseases linking to 467 outbreaks were reported to CDC.  Shigella was linked to 13 out of 467 outbreaks with 773 cases.  In Texas, 347 persons contracted Shigella sonnei gastroenteritis. The source was found to be shredded lettuce contaminated by an infected food handler. [16]
  • In 1987, 16,500 cases of foodborne diseases linking to 387 outbreaks were reported to CDC.  Shigella was associated with 9 out of 387 outbreaks with 6494 cases.  An outbreak of S. sonnei infection occurred at a mass gathering in a North Carolina forest. Thousands of attendees became ill; illness was associated with communal meals and poor hygienic conditions [16]
  • In 1988, 451 outbreaks involving 15,732 cases of foodborne diseases were reported to CDC of which 6 outbreaks were caused by Shigella.  A large outbreak of Shigella sonnei infections occurred among persons who ate raw tofu salad at an outdoor music festival in Michigan; 3,175 persons became ill and 117 of these persons were hospitalized. A large number of volunteers handled the ingredients, and ill food handlers apparently contaminated the salad during preparation. [17]
  • During 1989, 505 outbreaks involving 15,867 cases of foodborne diseases were reported to CDC of which 6 outbreaks were linked to Shigella. [17]
  • During 1990, 532 outbreaks involving 19,885 cases of foodborne diseases were reported to CDC out of which 8 outbreaks were associated with Shigella.  An outbreak involving 400 cases of S. sonnei infections was associated with food prepared by an infected food handler at a Texas restaurant. [17]
  • During 1991, 528 outbreaks involving 14,876 cases of foodborne diseases were reported to CDC of which 4 outbreaks were linked to Shigella. [17]
  • During 1992, 407 outbreaks involving 11,015 cases of foodborne diseases were reported to CDC of which one was linked to Shigella. [17]
  • During 1993–1997, a total of 2,751 outbreaks of foodborne diseases were reported (489 in 1993, 653 in 1994, 628 in 1995, 477 in 1996, and 504 in 1997). These outbreaks caused a reported 86,058 persons to become ill. Among outbreaks for which the etiology was determined, bacterial pathogens caused the largest percentage of outbreaks (75%) and the largest percentage of cases (86%).  Shigella caused 43 outbreaks with 1,555 total cases, most of which were caused by poor personal hygiene. [18]
  • During 1998–2002, the annual number of reported outbreaks ranged from 1,243 to 1,417.  The average annual number of outbreaks reported during this period (1,329) was substantially greater than the average annual number of outbreaks reported during 1993–1997 (550). The average number of cases per outbreak during 1998– 2002 (19) was lower than the average number of cases per outbreak during 1993–1997 (31). During 1998–2002, a total of 2,167 (33%) of the 6,647 outbreaks reported to CDC had a known etiology; these outbreaks accounted for 68,981 (54%) of 128,370 illnesses, of which 67 outbreaks with 3,677 cases and 1 death were linked to Shigella. [19]

Outbreaks

  1. Daniels et al. looked at outbreaks in the primary and secondary schools, colleges and universities from January 1, 1973 to December 31, 1997.  Local health departments reported 604 outbreaks of foodborne disease in the schools. In 60% of the outbreaks an etiology was not determined, and in 45% specific food vehicle of transmission was not determined.  The most commonly reported food preparation practices that contributed to these school-related outbreaks were improper food storage and holding temperatures, and food contaminated by a food handler.  Shigella was linked to 9 (1.5%) of 242 outbreaks, 1040 (2.1%) of 20,476 illnesses and 82 (5.4%) of 998 hospitalizations. [6]
  2. Musher et al. stated that “The high level of contagiousness of shigellosis may be inferred from the large number of secondary cases that follow a documented outbreak; persons who have varying degrees of contact with infection patients are likely, themselves to become infected. A very young child is the usual source.” [9]
  3. Rooney et al. conducted a review of outbreaks on a passenger ship from January 1, 1970 through June 30, 2003. They looked at 50 outbreaks of which 41 were linked to bacterial pathogens. Eight (16%) outbreaks were linked to Shigella leading to 2,076 total cases.  Rooney also stated that during the investigation of an outbreak of multiple antibiotic resistant Shigella flexneri 4a, investigators speculated that the spread of the infection by an infected foodhandler might have been facilitated by limited availability of toilet facilities for the galley crew.” [10] 

Shigellosis is characterized by an acute onset of diarrhea, fever, nausea, vomiting and abdominal cramps. Shigella species primarily infect the large intestine, causing clinical manifestations that range from watery or loose stools with minimal or no constitutional symptoms to more severe symptoms, including fever, abdominal cramps or tenderness, tenesmus, and mucoid stools with or without blood. Complications include toxic megacolon and reactive arthritis. Rarely hemolytic uremic syndrome can occur. Illness is usually self-limited and lasts from several days to weeks with an average of four to seven days. The severity of the infection depends on host factors such as age, nutritional status and the serotype. Infections with Shigella sonnei usually result in a short clinical course and low case fatality rate. In contrast, Shigella dysenteriae is often associated with a serious disease and a high case fatality rate. [1, 2, 7]
Organism: Shigella species are aerobic, gram-negative bacilli in the family Enterobacteriaceae. The genus Shigella consists of four species: Group A Shigella dysenteriae, Group B Shigella flexneri, Group C Shigella boydii, and Group D Shigella sonnei.  Groups A, B and C are further divided into approximately 40 serotypes, designated by numbers. Among Shigella isolates reported in the United States in 2003, approximately 88% were Shigella sonnei, 11% were Shigella flexneri, 1% was Shigella boydii, and 0.3% was Shigella dysenteriae. Shigella dysenteriae is rare in the United States but is an endemic in rural Africa and the Indian subcontinent. [1, 2, 7]
Reservoir of infection: Humans are the natural host for Shigella, although other primates may be infected. [1, 2, 3, 7]
           
Modes of transmission: The primary mode of transmission is fecal-oral. Children that are five years of age or younger in a child care settings, their caregivers, and other people living in crowded conditions are at increased risk of infection. Travel to resource-limited countries with inadequate sanitation may place the traveler at risk of infection.  Predominant modes of transmission include person-to-person contact, contact with a contaminated inanimate object, ingestion of contaminated food or water, and sexual contact. Houseflies also may be vectors through physical transport of infected feces. Shigella flexneri, S boydii, and S dysenteriae infections are more common in older children and adults, and these infections often are associated with sources outside the United States. [1, 2, 7]
Attack rates:

  • Two-thirds of the cases and most of the deaths worldwide are in children less than ten years. The disease is rare in infants under six months of age, particularly those who are breastfed.  Secondary attack rates in households may be as high as 40%. [1]
  • Attack rate is highest in children <5 years of age in a daycare setting, their caregivers, and other people living in crowded conditions. [3,7,9]  
  • 33% to 75% in daycare centers and 25% within the family of an infected child. [9] 
  • According to Mohle-Boetani et al. “in 58% of families with shigellosis, the first person with diarrhea during the outbreak was a child younger than 6 years; 92% of diarrheal illnesses among those children were attributable to day-care attendance.” [20]

Infectious dose: The infectious dose required to produce disease can be as few as 10 to 200 organisms, but depends on the Shigella species. [1, 2, 7]
Incubation Period The incubation period depends on the serotype. It varies from twelve hours to seven days but is usually 2 to 4 days. [1, 2, 5, 7]
Infectious Period: Shigella is communicable during the acute phase and while the infectious agent is present in feces which is usually no longer than four weeks. Asymptomatic carriage and excretion may persist for months. [1, 5, 7]
Asymptomatic carrier state: Asymptomatic infections occur and carriage may persist for months. [1, 7]

Diagnosis:  Isolation of Shigella from feces or rectal swab specimens containing feces is diagnostic but lacks sensitivity. The presence of fecal leukocytes on a methylene-blue stained stool smear is sensitive for the diagnosis of colitis but is not specific for Shigella species. An enzyme immunoassay for Shiga toxin may be useful for detection of S dysenteriae type 1 in stool. Although bacteremia is rare, blood should be cultured in severely ill, immunocompromised, or malnourished patients. Other testing modalities that are available in research laboratories include the fluorescent antibody test, polymerase chain reaction assay, and enzyme-linked DNA probes. [1, 2]
Preventive Measures
Exclusions:

  1. Australian Blue Book-Guidelines for the control of infectious diseases suggest that antibiotics should be considered on the bases of the serotype, severity of illness and host characteristics, for example, if they are a child in a child care setting, a food handler or suffering from a chronic illness.  They also suggest that food handlers should be excluded from work until two negative stools have been obtained or until at least 48 hours after the diarrhea has ceased and rigid personal hygiene measures can be assured.  Same applies to the symptomatic contacts. [1]  Guidelines and Consensus Document {Grade III-A}
  2. The Red Book published by the American Academy of Pediatrics states that “The most difficult outbreaks to control are those that involve young children (not yet toilet-trained), adults who are unable to care for themselves (mentally disabled individuals or skilled nursing facility residents), or an inadequate water supply.  When Shigella infection is identified in a child care attendee or staff member, stool specimens from other symptomatic attendees and staff members should be cultured. Stool specimens from household contacts who have diarrhea also should be cultured. All symptomatic people whose stool specimens yield Shigella should receive appropriate antimicrobial therapy and should not be permitted to reenter the child care facility until diarrhea has ceased and stool cultures test negative for Shigella. Strict attention to hand hygiene is essential to limit spread. Other important control measures include improved sanitation, safe water supply through chlorination, proper cooking and storage of food, exclusion of infected people as food handlers, and measures to decrease contamination of food by houseflies. People with diarrhea caused by this potentially waterborne pathogen should not use recreational water venues (e.g., swimming pools, lakes, rivers, the ocean) for 2 weeks after symptoms resolve.” [2] Guidelines and Consensus Document {Grade III-A}
  3. Public Health Laboratory Service Advisory Committee on Gastrointestinal infections in their “Preventing Person to Person Spread Following Gastrointestinal Infections: Guidelines for Public Health Physicians and Environmental Health officers” suggest that exclusion for Shigella sonnei, 48 hours after first normal stool and two negative fecal specimens taken at interval of not less than 48 hours for Shigella dysenteriae, Shigella flexneri, and Shigella boydii. [3] Guidelines and Consensus Document {Grade III-A}
  4. A guideline produced by Ontario Medical Association and the Ontario Hospital Association suggests following the specific exclusion for shigellosis and exclusions in case of outbreak. [4] Guidelines and Consensus Document {Grade III-A}
    1.  Persons with symptoms suggestive of Shigella must submit stool specimens for culture. If Shigella is cultured, the person must be excluded from food handling and patient care activities until two negative stools have been obtained, 24 hours apart, beginning at least 24 hours after diarrhea ends. If treated with antibiotics, the first stool must be submitted at least 48 hours after the last dose.
    2. Exclusion in outbreak situations
      1. Food handlers and epidemiologically-linked patient care workers may be asked to submit stools for examination. Symptomatic persons must remain off work until two stool specimens are negative for the outbreak pathogen; the stools must be collected at least 24 hours apart, with the first being collected after at least 24 hours without diarrhea. If the individual has been treated with antibiotics, the first stool must not be submitted until at least 48 hours following cessation of the antibiotic.
      2. Asymptomatic persons should not work during an outbreak if their stool specimens are positive for the outbreak pathogen. Once the outbreak is declared over by the Medical Officer of Health, asymptomatic carriers of the outbreak pathogen may return to work. Prior to returning to work, all staff must be assessed and instructed in personal hygiene and high-risk food preparation, either by hospital staff, or by public health inspection staff
  5. Richardson M, et al. concluded from the evidence based research that children under the age of 5 years should be excluded until at least one negative stool and children over the age of 5 years have 24 hours since the last episode of diarrhea.  Hygiene measures are most important in control.  Also states that exclusion will not be fully effective because asymptomatic infections occur and may be involved in transmission. [5] Evidence based reviews with guidelines formed out of reviewed literary sources {Grade III-A}
  6. Daniels et al. states that “several outbreaks in schools have been attributed to contamination of food by food-handlers who worked while ill or had poor personal hygiene.  In our review of reported foodborne outbreaks in school, 57% of outbreaks were attributed to likely contamination by a food-handler. The adoption of a work policy that includes paid leave for food handlers with gastroenteritis would probably increase compliance with illness related work exclusion policies. Training and certifying all food handlers in school cafeterias in specific techniques, such as good personal hygiene, adequate hand washing, proper cooling and reheating of foods and methods of preventing cross-contamination between cooked and raw foods, would also likely reduce the incidence of foodborne disease outbreaks.” [6] Review of Outbreaks and Epidemiology {Grade III-A}
  7. Guerrant et al. suggest two preventive measures in the guidelines for the management of infectious diarrhea. [8] Evidence based reviews with guidelines formed out of reviewed literary sources {Grade III-A}
    1. Diagnostic fecal testing for Public Health reasons.
      1. “Diagnostic testing of stool specimens is indicated for certain groups of people who are not themselves patients. Food-handlers in food service establishments and health care workers involved in direct patient care should be tested for bacterial pathogens if they have diarrhea because of their potential to transmit infection to large numbers of persons. Similarly, diarrheal illness in a day-care attendee, day-care employee, or resident of an institutional facility (e.g., psychiatric hospital, prison, or nursing home) should be evaluated for bacterial or parasitic infection because gastrointestinal illnesses in these settings may indicate that a disease outbreak is occurring.”
    2. Follow-up testing
      1. “In certain situations, assurance should be obtained that a patient with a laboratory-confirmed bacterial or parasitic diarrheal disease has been cured or is no longer a fecal carrier. Because food-handlers and health care workers can transmit bacterial and parasitic diseases even if they are asymptomatic, it is recommended that before returning to their jobs these individuals have 2 consecutive negative stool samples taken 24 h apart and at least 48 h after resolution of symptoms. If the patient has received antimicrobial therapy, the first stool specimen should be obtained at least 48 h after the last dose. Furthermore, if food-handlers or health care workers are symptomatic, they should be excluded from directly handling food and from caring for high-risk patients.”
  8. Rooney et al. suggested that “strict hygiene measures, such as frequent hand washing, thoroughly washing ready-to-eat foods that require handling but no subsequent cooking (e.g., salads), and excluding infected food handlers from work, are necessary to ensure that food does not facilitate the spread of the infection on a ship.” [10] Review of Outbreaks and Epidemiology {Grade III-A}
  9. Cruickshank states that “during the acute stages of gastroenteritis large numbers of organisms are excreted and by the nature of the disease are likely to be widely dispersed; clearly, food handlers who are symptomatically ill may present a real hazard and should be excluded from work.”  He also stated that “in line with other expert bodies it concluded that asymptomatic carriers of non-typhoid salmonella and Shigella organisms, Vibrio cholerae, and enteric viruses who practice good hygiene do not constitute a significant risk.” [11] Evidence Based Literature {Grade III-A}
  10. According to Mohle-Boetani et al., “caring for convalescing asymptomatic children was reported to be effective in curtailing a shigellosis outbreak in a day-care in Seattle.”[20] Review of Outbreaks and Epidemiology {Grade II-A}

References

    1. The Communicable Diseases Section, Public Health Group, Victorian Department of Human Services, Australia.  Blue book - Guidelines for the control of infectious diseases revised edition 2005. Guidelines and Consensus Document
    2. American Academy of Pediatrics. Red Book – The Report of the Committee of Infectious Diseases. 2006 Edition.  Guidelines and Consensus Document
    3. PHLS Advisory Committee on Gastrointestinal infections. Preventing Person to Person Spread Following Gastrointestinal Infections: Guidelines for Public Health Physicians and Environmental Health officers. Communicable Disease and Public Health 2004; 7(4):362-384. Guidelines and Consensus Document
    4. Ontario Medical Association and the Ontario Hospital Association. Enteric Diseases Surveillance Protocol for Ontario Hospitals. Published November 989/Revised/Reviewed June 2005 Guidelines and Consensus Document
    5. Richardson M, Elliman D, Maguire H, et al. Evidence base of incubation periods, periods of infectiousness and exclusion policies for the control of communicable diseases in schools and preschools. Pediatric ID Journal Vol. 20 April 2001; 380-391 Evidence based reviews with guidelines formed out of reviewed literary sources
    6. Daniels NA, Mackinnon L, et al. Foodborne disease outbreaks in United States schools. Pediatr Infect Dis J, 2002;21:623-8 Review of Outbreaks and Epidemiology
    7. Dennehy, PH. Acute Diarrheal Disease in Children: Epidemiology, Prevention, and Treatment. Infect Dis Clin N Am 19 (2005) 585-602 Evidence Based Literature
    8. Guerrant, RL, Gilder TV, Steiner TS.  Practice Guidelines for the Management of Infection Diarrhea. CID 2001;32:331-50 Evidence based reviews with guidelines formed out of reviewed literary sources
    9. Musher DM, Musher BL. Contagious Acute Gastrointestinal Infections. N Engl J Med 2004;351:2417-27 Evidence Based Literature
    10. Rooney RM, Cramer EH, Mantha S, et al. A Review of Outbreaks of Foodborne Disease Associated with Passenger Ships: Evidence for Risk Management. Public Health Reports, Volume 19, July-August 2004 Review of Outbreaks and Epidemiology
    11. Cruickshank JG. Food handlers and food poisoning. BMJ January 1990, Volume 300 Evidence Based Literature
    12. AAP.  Managing Infection Diseases in Child Care and Schools: A Quick Reference Guide Aronson SS, Shope TR eds. Chapter 5.  Accessed on 7/30/07 at www.aap.org  Guidelines and Consensus Document
    13. UK’s Health Protection Agency.  Guidelines on the Management of Communicable Diseases in School and Nurseries.  Accessed at http://www.hpa.org.uk/infections/topics_az/schools/schools.pdf  Guidelines and Consensus Document
    14. BCCDC. Communicable Disease Control Exclusion of Enteric Cases and their Contracts from High Risk Settings. April 2007. Accessed at http://www.bccdc.org/download.php?item=3111  Guidelines and Consensus Document
    15. APHA, AAP, & NRCHS. Exclusion and Inclusion of Ill Children in Child Care Facilities and Care of Ill Children in Child Care. National Health and Safety Performance Standards: Guidelines for Out-of-Home Child Care. Second Edition. 2002. A Joint Collaborative Project of The American Academy of Pediatrics Elk Grove Village, IL., The American Public Health Association Washington, D.C. & The National Resource Center for Health and Safety in Child Care, University of Colorado Health Sciences Center at Fitzsimons Campus Aurora, CO. Guidelines and Consensus Document
    16. CDC. Foodborne Disease Outbreaks, 5-Year Summary, 1983-1987. MMWR March 01, 1990/39 (SS01);15-23 Review of Outbreaks and Epidemiology
    17. CDC. Surveillance for Foodborne-Disease Outbreaks – United States, 1988-1992. MMWR October 25, 1996 Vol. 45 / No. SS-5 Review of Outbreaks and Epidemiology
    18. CDC. Surveillance for Foodborne-Disease Outbreaks – United States, 1993-1997.  MMWR March 17, 2000 /Vol. 49 /No. SS-1 Review of Outbreaks and Epidemiology
    19. CDC. Surveillance for Foodborne-Disease Outbreaks – United States, 1998-2002. MMWR November 10, 2006 Vol. 55/ SS-10 Review of Outbreaks and Epidemiology
    20. Mohle-Boetani JC, Stapleton M, Finger R, et al. Communitywide Shigellosis: Control of an Outbreak and Risk Factors in Child Day-Care Centers. American Journal of Public Health June 1995, Vol. 85, No. 6 Review of Outbreaks and Epidemiology
    21. Trevejo RT, Abbott ST, Wolfe MI, et al. An Untypeable Shigella flexneri Strain associated with an Outbreak in California. Review of Outbreaks and Epidemiology
    22. Public Health Laboratory Service, Advisory Committee on Gastrointestinal infections. Preventing Person to Person Spread Following Gastrointestinal Infections: Guidelines for Public Health Physicians and Environmental Health officers. Communicable Disease and Public Health 2004; 7(4):362-384. Guidelines and Consensus document