Shigellosis generally causes less morbidity and mortality in high-income countries than in low- and middle-income countries. This is mostly due to the causative agent being Shigella sonnei in high-income countries, which is associated with a less severe illness.[4]Kotloff KL, Winickoff JP, Ivanoff B, et al. Global burden of Shigella infections: implications for vaccine development and implementation of control strategies. Bull World Health Organ. 1999;77(8):651-66.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2557719/pdf/10516787.pdf
http://www.ncbi.nlm.nih.gov/pubmed/10516787?tool=bestpractice.com
[5]Gastrointestinal infections and food poisoning. In: Bannister BA, Gillespie SH, Jones J. Infection: microbiology and management. 3rd ed. Oxford, UK: Blackwell Publishing Ltd.; 2006:167-201. Easier access to primary care (and specialist care if required) is also a likely contributor.
Prognosis
In otherwise healthy adults, most cases of shigellosis are mild and self-limiting, and chronic carriage is uncommon.[6]Kotloff KL, Riddle MS, Platts-Mills JA, et al. Shigellosis. Lancet. 2018 Feb 24;391(10122):801-12.
http://www.ncbi.nlm.nih.gov/pubmed/29254859?tool=bestpractice.com
Without antibiotics the course of the illness may last slightly longer, and shedding of organisms in the stool may continue for up to 6 weeks.[5]Gastrointestinal infections and food poisoning. In: Bannister BA, Gillespie SH, Jones J. Infection: microbiology and management. 3rd ed. Oxford, UK: Blackwell Publishing Ltd.; 2006:167-201.
Shigella is the second most common cause of diarrhoea-related death globally.[45]GBD 2016 Diarrhoeal Disease Collaborators. Estimates of the global, regional, and national morbidity, mortality, and aetiologies of diarrhoea in 195 countries: a systematic analysis for the Global Burden of Disease Study 2016. Lancet Infect Dis. 2018 Nov;18(11):1211-28.
https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(18)30362-1/fulltext
http://www.ncbi.nlm.nih.gov/pubmed/30243583?tool=bestpractice.com
Mortality is highest in south Asia and sub-Saharan Africa.[6]Kotloff KL, Riddle MS, Platts-Mills JA, et al. Shigellosis. Lancet. 2018 Feb 24;391(10122):801-12.
http://www.ncbi.nlm.nih.gov/pubmed/29254859?tool=bestpractice.com
One meta-analysis found that Shigella infection was significantly associated with mortality in children in resource-limited settings, but dysentery was not.[46]Tickell KD, Brander RL, Atlas HE, et al. Identification and management of Shigella infection in children with diarrhoea: a systematic review and meta-analysis. Lancet Glob Health. 2017 Dec;5(12):e1235-48.
https://www.thelancet.com/journals/langlo/article/PIIS2214-109X(17)30392-3/fulltext
http://www.ncbi.nlm.nih.gov/pubmed/29132613?tool=bestpractice.com
Reliance on dysentery to identify children with Shigella infection may not adequately identify children at risk of death.[46]Tickell KD, Brander RL, Atlas HE, et al. Identification and management of Shigella infection in children with diarrhoea: a systematic review and meta-analysis. Lancet Glob Health. 2017 Dec;5(12):e1235-48.
https://www.thelancet.com/journals/langlo/article/PIIS2214-109X(17)30392-3/fulltext
http://www.ncbi.nlm.nih.gov/pubmed/29132613?tool=bestpractice.com
In high-income countries, even with more severe disease, mortality is very low, estimated at 0.1% in the US.[10]Marder EP, Cieslak PR, Cronquist AB, et al. Incidence and trends of infections with pathogens transmitted commonly through food and the effect of increasing use of culture-independent diagnostic tests on surveillance - Foodborne Diseases Active Surveillance Network, 10 US sites, 2013-2016. MMWR Morb Mortal Wkly Rep. 2017 Apr 21;66(15):397-403.
https://www.cdc.gov/mmwr/volumes/66/wr/mm6615a1.htm
http://www.ncbi.nlm.nih.gov/pubmed/28426643?tool=bestpractice.com