More than half of Salmonella infections in Ireland last year were associated with international travel, according to a recent report.
During 2018, 363 people had salmonellosis including 349 confirmed and 14 probable compared to 414 in 2017 based on figures from the Health Protection Surveillance Centre (HPSC), Ireland’s agency for the surveillance of communicable diseases and part of the Health Service Executive (HSE).
The 363 cases in 2018 represent a 12 percent decrease on 2017; when only confirmed cases are compared, the 349 in 2018 represent an 8 percent decrease versus 2017. One large outbreak of Salmonella Brandenburg affected 71 people in 2017.
Travel-associated infections and outbreaks
Overall, notifications increased 40 percent from a low of 260 cases in 2014, but remain below levels of 2007 to 2008. The increase since 2014 is more pronounced among travel-associated infections which are up 113 percent, with an increase of 22 percent among domestically-acquired cases.
Where country of infection was reported, 51 percent, or 166 of 328 cases were travel-associated. There was a peak between July and October coinciding with the summer holiday period.
Among travel associated cases, the top countries of infection included 31 ill after going to from Spain, 27 from Bosnia and Herzegovina, 13 from Thailand, and 10 from India. The unusual high number linked with travel to Bosnia and Herzegovina was an outbreak.
This international outbreak of Salmonella monophasic Typhimurium, sequence type 19 was among members of a pilgrimage group returning from Medjugorje, Bosnia and Herzegovina in September 2018. More cases of salmonellosis in travellers returning from Medjugorje were reported from other areas in the country and another EU country, indicating it was a wider event.
In total, 29 cases were identified among Irish residents; 18 of whom were laboratory confirmed. Their age range was 42 to 83 years old. They occurred over a one month period, the earliest onset was in September and the latest in October. The source of infection was not identified but many of those ill recalled consuming eggs.
One cluster of six cases of Salmonella Enteritidis in 2018 was genetically linked to an EU outbreak associated with Polish eggs. ECDC and EFSA are currently updating this multi-country outbreak with publication expected by late January 2020.
Two apparently sporadic salmonellosis cases were genetically linked to other international outbreaks identified in Europe. One of these was part of a multi-country Salmonella Agona outbreak linked to ready-to-eat products containing cucumbers.
Number of people needing hospital treatment
There was another foodborne family outbreak with seven ill; a family meal was the suspected vehicle of transmission. Three remaining outbreaks were small with two to three cases each; two were suspected foodborne travel-related incidents and person-to-person transmission was reported for the other.
The highest age-specific incidence rate was in children under five years which is likely influenced by clinicians more readily seeking clinical samples in that age group. The next highest rate was in the 20 to 24 years old group while the lowest rate this year was in the 15 to 19 age group.
Diarrhea was the most common symptom among notified cases in 2018, followed by abdominal pain. Bloody diarrhoea occurred amongst a third of cases. Median duration of illness was eight days with a range of one to 67 days, based on 192 cases. A total of 135 people were hospitalised compared to 124 in 2017.
Salmonella Enteritidis and Typhimurium including monophasic Typhimurium were the most common serotypes followed by Newport.
Disease acquired in Ireland was more commonly caused by Salmonella Typhimurium and monophasic Typhimurium strains than by Salmonella Enteritidis strains. Illness in Europe was mostly associated with Salmonella Enteritidis, followed by Typhimurium including monophasic Typhimurium strains.
For cases from the rest of the world, non-Enteritidis, non-Typhimurium cases predominated, with Salmonella Enteritidis making up for 20 percent and Typhimurium including monophasic Typhimurium strains accounting for 23 percent of cases.
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