History and exam

Key diagnostic factors

common

presence of risk factors

Exposure to contaminated water/food, direct faecal-oral contact, aged <5 years, malnutrition, poor hygiene and cramped conditions, and travel to endemic areas are strong risk factors.[3][4][5]​​​[6][11]​[16][17]​​​​​​​

diarrhoea

Initially watery and profuse.

Blood and mucus may be seen.[24]​ May be low volume, because the source is mostly colonic.[5]

Shigella dysenteriaeand Sflexneri often cause a more severe illness, with fever and worsening bloody diarrhoea with mucus.

cramping abdominal pain

Common feature of shigellosis.

fever

Common feature of shigellosis. Often associated with leukocytosis in extremely ill patients.[5]

tenesmus

Common feature of shigellosis.

abdominal pain or tenderness

Generalised abdominal pain and lower abdominal tenderness are often present.

uncommon

features of haemolytic uraemic syndrome

Associated with Shigella dysenteriae type 1.[12]

Clinical features include oligo-anuria, signs of renal failure, fluid overload, and hypertension.[29][30]

Serious bleeding is rare. Neurological features include irritability, seizures, and confusion (due to cerebrovascular microthrombi, hypertension, electrolyte imbalance, or uraemia). Rarely, intestinal necrosis or pancreatic involvement occurs.

Other diagnostic factors

common

signs of volume depletion

Mild self-limiting shigellosis may cause volume depletion. More severe volume depletion is associated with Shigella dysenteriae and S flexneri.

Signs may include orthostatic hypotension, dry mucous membranes, or poor skin turgor. In infants, nappies may be dry.

increased bowel sounds

Bowel sounds may be normal or increased.

uncommon

vomiting

May be occasionally reported.

meningism or other signs of altered neurological status

May indicate Shigella-induced encephalopathy, especially in children.

febrile seizures

Especially in young children.

somnolence

Especially in children.

Somnolence may also suggest haemolytic uraemic syndrome, but is not definitive.

Risk factors

strong

exposure to contaminated water or food or direct faecal-oral contact

Shigella species can survive in stomach acid, and therefore infection can be caused by as few as 10 to 100 organisms.[11] It may be acquired readily with exposure to contaminated water or food or by the direct faecal-oral route.

Shigellosis has also been transmitted by flies.[16]

age <5 years

Children age <5 years account for the majority of reported shigellosis cases in the US and globally.[2][3]​​​​​

malnutrition

In high-income countries, Shigella usually causes a mild, self-limiting illness. In low and middle-income countries where S dysenteriae is more prevalent, shigellosis causes a more severe illness. This is exacerbated in the presence of coexistent malnutrition.[17] A vicious cycle of prolonged diarrhoea and illness associated with deteriorating malnutrition can occur.

poor hygiene and cramped conditions

Outbreaks of Shigella commonly occur in institutions such as psychiatric units, children's nurseries, and prisons. Poor hygiene and cramped conditions, coupled with the requirement of a low inoculating load, contribute significantly.[5]

travel to endemic areas

A significant proportion of traveller's diarrhoea is attributed to Shigella.[13][18][19] The acquired Shigella species may be different from the usual species isolated in the traveller's home area and have more antibiotic resistance, leading to prolonged and widespread outbreaks.

weak

men who have sex with men

Sexual transmission ofShigella infection has been increasingly reported, particularly among gay, bisexual, and other men who have sex with men (MSM).[9][20]​​​

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