Epidemiology

Salmonella is one of the most commonly identified causes of foodborne illnesses in the US and Europe, and is one of the four key global causes of diarrheal diseases.[4][5][6][7][8]​​ WHO: Salmonella (non-typhoidal) fact sheet Opens in new window

Campylobacter and Salmonella are the leading bacterial causes of foodborne enteritis, whereas Clostridioides difficile (C difficile) is the pathogen most frequently detected in US adult outpatients with acute infective gastroenteritis overall.[9][10]​​​ Salmonellosis is estimated to cause approximately 1.35 million illnesses each year in the US, with 26,500 hospitalizations and 420 deaths.[11]​​

The incidence rate of infection is approximately 16 cases per 100,000 population.[9]Salmonella accounts for 30% of all deaths associated with foodborne disease in the US.[5]

Infants and young children are at highest risk for the disease, although nontyphoidal Salmonella are a frequent cause of gastroenteritis among adults as well. In addition, older people are at higher risk than young to middle-aged adults. Outbreaks of salmonellosis among older people residing in long-term care facilities have been reported.[12] People at the extremes of age are also at risk for more severe, complicated infections. Most infections occur during the warmer months of the year (May to October), similar to other (but not all) types of foodborne diseases.

While poultry is the food vehicle most frequently implicated in deaths due to Salmonella infection, raw produce accounts for nearly one-half of all outbreaks.[9][13]​​[14]​ A nationwide outbreak of salmonellosis (S Saintpaul) occurred in the US in 2008 resulting in 1500 documented cases; 21% of patients were hospitalized.[15] Jalapeño and/or serrano peppers were implicated in the outbreak, highlighting the importance of preventing contamination of raw produce.[15] Multistate outbreaks linked to ground beef have also been investigated in the US.[16]

An increase in the number of households raising poultry in the US has resulted in an increasing number of Salmonella infections linked to contact with backyard poultry.[17]​​

Nontyphoidal Salmonella infection is also common in low- and middle-income countries in Asia, Africa, and South America, where it is an important cause of infantile and childhood diarrhea.[18][19][20]​ One study estimated that 93.8 million cases of gastroenteritis due to Salmonella species occur globally each year.[21] One systematic analysis for the Global Burden of Disease Study 2019 estimates that nontyphoidal Salmonella was responsible for 215,000 deaths worldwide (95% CI 135,000-327,000), with 40% of deaths attributable to bloodstream infections.[22] 

In addition to gastroenteritis, invasive bloodstream infections due to nontyphoidal Salmonella occur especially among children with malaria and malnutrition, and among adults with HIV.

The annual incidence of invasive nontyphoidal Salmonella disease among children in Africa is 175-388 per 100,000 cases compared with 1 per 100,000 cases in high-income countries.[23] The majority of invasive cases in sub-Saharan Africa are caused by specific lineages of multidrug-resistant (nontyphoidal) S Typhimurium and S Enteritidis.[24][25][26]​​ Persons living with HIV/AIDS are at increased risk of infection, and genetic and epidemiologic evidence suggests person-to-person spread.[27][28][29]

Travelers can acquire Salmonella as a cause of traveler's diarrhea, but overall this is infrequent compared with other causes of traveler's diarrhea, such as enterotoxigenic Escherichia coli (E Coli).[30]

Chronic carrier state

A chronic carrier state is defined as positive stool or urine culture for Salmonella at 12 months or more following the acute illness.[31]

Chronic carriage of nontyphoidal Salmonella occurs in 0.5% of cases, compared with 3% of those with S Typhi.[32] Carriage beyond one year is unusual, and lifelong carriage has not been demonstrated, in contrast to S Typhi.[33] Certain groups are at higher risk for chronic carriage, including infants, women, patients with gallstones or kidney stones, and patients coinfected with Schistosoma haematobium.

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