Epidemiology of Salmonella infections reported in a northern California county

Background: In 2003, 43,657 cases of salmonellosis were reported in the USA. S. typhimurium and S. enteritidis were the serotypes most frequently isolated in 2000, accounting for 42% of all laboratory-confirmed cases. Since then, S. typhimurium has decreased in incidence. Methods: We reviewed the 2007 typhoidal and nontyphoidal Salmonella Confidential Morbidity Reports (CMRs) and abstracted specimen source, basic demographic information, clinical information, antibiotic/food/animal/water exposures, antibiotic resistance patterns along with travel and vaccine history for patients with S. typhi. Results: 116 nontyphoidal Salmonella and 11 typhoidal Salmonella infections were reported to our county. 2 asymptomatic typhoid carriers were identified. The mean age of typhoid cases was 25 years; 55% were hospitalized. 72% of cases presented with fever and headaches. 54% of infections occurred in foreign-born. Asian Pacific Islanders were disproportionately affected (45%). 55% had recently traveled abroad. None were vaccinated. The most common non-typhoidal serotype was S. enteritidis (23 cases), followed by newport (12) and typhimurium and heidelberg (10 each). 72% of these cases presented with diarrhea, often during spring/summer. Mean age was 33. 13% were hospitalized. The majority of newport cases occurred amongst Hispanics. Conclusions: S. typhi remains a disease of travelers and immigrants although contact with an asymptomatic chronic carrier is a risk factor. Vaccination rates remain low. Non-typhoidal infections remain common, demonstrating the need for education of the public regarding transmission mechanisms, including exposure to pets and contaminated food items. Newport was the 2nd most common serotype in our study possibly reflecting our county's large migrant worker population.