Reporting Obligations

Individuals with suspect or confirmed cases must be reported to the Thunder Bay District Health Unit by the next working day by fax, phone or mail.

  • Fax: (807) 625-4822
  • Phone: 625-5930 or toll-free at 1-888-294-6630, ext. 5930
  • Mail: 999 Balmoral Street, Thunder Bay, ON P7B 6E7


NEWS - Extensively Drug Resistant (XDR) Shigella - March 2023

Public Health Ontario (PHO) is monitoring trends related to extensively drug resistant (XDR) Shigella cases in Ontario (at least ten cases, all male, of XDR Shigella sonnei)  that are resistant to all commonly recommended antibiotics.

Sexual contact between men who have sex with men (MSM) has been identified as the predominant route of transmission. In addition, three of the nine cases also travelled aboard (England, Ireland, Luxemburg, Portugal and United States) in 2022.

This XDR Shigella strain is currently defined as resistant to the following five antimicrobials: ampicillin, fluoroquinolones, third-generation cephalosporins, azithromycin, and trimethoprim-sulfamethoxazole. This leaves limited treatment options available that have documented clinical success for shigellosis.

For more information, See memo from Dr. Yaffe, Associate Chief Medical Officer of Health for Ontario: XDR Shigella sonnei: Possible Sexual Transmission.



Aetiologic Agent:

Shigellosis is an acute bacterial disease, also known as bacillary dysentery, caused by facultative anaerobic, gram-negative bacilli in the family Enterobacteriaceae. There are four subgroups, which have traditionally been regarded as separate species with more than 40 serotypes identified.

  1. Group A: Shigella dysenteriae
  2. Group B: Shigella flexneri
  3. Group C: Shigella boydii
  4. Group D: Shigella sonnei

Species A, B, and C are further classified into 15, 8, and 19 serotypes, respectively. Group D (Shigella sonnei) consists of a single serotype.

The infectious dose for humans is low; as few as 10-100 bacteria have been shown to cause disease.

Clinical Presentation:

An acute bacterial disease characterized by watery, loose stools, fever, nausea and vomiting in mild cases. Sometimes, toxaemia, abdominal cramps and tenesmus with mucoid stools with or without blood in more severe cases. Illness is usually self-limiting, lasting an average of 4 – 7 days. Severity and case-fatality vary with the age of the host and the serotype of Shigella

Modes of transmission:

Primary mode of transmission is fecal-oral. Transmission occurs through person-to-person contact, contact with contaminated inanimate objects, ingestion of contaminated food or water and through sexual contact. Multi-antibiotic resistant strains have appeared worldwide, resulting from wide spread use of antibiotics.

Prolonged organism survival in water (up to 6 months) and food (up to 30 days) can occur with Shigella species. Direct transmission is common in children and infected persons who do not thoroughly clean their hands. Risk of transmission increases for individuals engaging in anal-oral sex or in settings where personal hygiene is inadequate, such as in daycare centres. Flies also may be vectors through physical transport of organisms from infected feces to uncovered food items.

Foodborne outbreaks of shigellosis associated with an infected food handler has occurred in Ontario.

Incubation Period:

Usually 1-3 days but may range from 12 - 96 hours and up to one week for S. Dysenteriae.

Period of Communicability:

During acute infection and until the infectious agent is no longer present in feces, usually within 4 weeks after illness. Secondary attack rates in households can be as high as 40%. Asymptomatic carriers may transmit infection.

Appropriate antimicrobial treatment usually reduces duration of carriage to a few days.


Risk Factors/Susceptibility

The elderly, the debilitated and the malnourished of all ages are particularly susceptible to severe disease and death.

• Men who have sex with men – see NEWS section at the top of the page concerning XDR Shigella

• Situations of overcrowding where sanitation is poor, such as jails, institutions for children, daycare centres and mental hospitals

• Anal-oral contact

• Consumption of raw/unwashed produce or undercooked shellfish

• Poor hand hygiene

• Recreational water contact (sewage contaminated water)

• History of travel outside province/country


Diagnosis & Laboratory Testing

Diagnosis is made through the isolation of Shigella spp. from feces or rectal swab. Shigella remains viable outside the body for only a short period of time, therefore specimens need to be processed rapidly after collection.

Testing Information & Requisition


Treatment & Case Management

Take a sexual history if shigellosis is suspected.

If concerned about sexually transmitted proctocolitis or enteritis test for other STIs and bloodborne infections, including HIV, syphilis, gonorrhea, chlamydia, hepatitis B and hepatitis C at exposed sites as appropriate.

Treatment and follow up is under the direction of the attending health care provider.

Consider the following:

  • Oral rehydration/electrolyte replacement is essential in patients who are dehydrated
  • Most patients (regardless of XDR results) will improve without antibiotic therapy
  • Antibiotic therapy is only recommended for patients with severe disease (e.g. hospitalized patients) or immunocompromised patients
  • In those who require antibiotics, therapy should be guided by antimicrobial susceptibility testing, in consultation with an infectious disease specialist or other clinician knowledgeable in treating antibiotic-resistant bacteria.

Query if any other household members have symptoms consistent with shigellosis.

Exclusion from work, school or child care

Exclude symptomatic cases who are food handlers, healthcare providers, caregivers or child care attendees pending a negative stool sample or rectal swab collected at least 24 hours after cessation of symptoms OR 48 hours after completion of antibiotic therapy.

General Counselling

Provide information to patients on personal prevention measures (careful hand hygiene after defecation, sexual contact and before preparing or eating food).

Individuals should be counselled to avoid public recreational water facilities such as public pools, hot tubs, spas, and splash pads.

Counselling specific to sexual activity

  • Sexual activity should be avoided from symptom onset until at least seven days after symptoms have stopped.
  • Faecal-oral contact during sexual activity should be avoided for four to six weeks, in consideration of the shedding period for shigellosis.
  • Hygiene measures should be completed prior to sexual activity to potentially reduce fecal-oral exposure and include the following:
    • wash genital and anal areas and complete hand washing before and after sexual activity
    • use latex gloves for fingering or fisting and dental dams during oral-anal sex
    • refrain from sharing sex toys and ensure proper cleaning and disinfection after their use and between partners.
    • change condoms between anal and oral sex
  • Practice safe sex by using condom to reduce the risk of acquiring other sexually transmitted infections, including HIV and hepatitis B and C.


Patient Information

Patient Fact Sheet



  1.  Ministry of Health and Long Term Care, Infectious Diseases Protocol - Appendix 1 (2022) Shigellosis.
  2. Dr. B. Yaffee, Associate Chief Medical Officer of Health, Memo -  XDR Shigella sonnei: Possible Sexual Transmission – March 16, 2023


Additional Resources

PHAC. "Shigellosis Factsheet"

Heymann, D.L. Control of Communicable Disease Manual (20th Ed.). Washington, American Public Health Association, 2015.

Additional resources specific to XDR Shigellosis

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