Salmonellosis
Acute gastroenteritis associated with Salmonella infections in humans is, in most cases, self-limiting within a few days or weeks, but for some patients the disease is fatal. Studies estimated the duration to be 5.58 days for gastroenteritis cases not requiring medical help, 10.65 days for gastroenteritis cases visiting a doctor but not hospitalised and 16.15 days for hospitalised gastroenteritis cases (Kemmeren 2006).
The proportion of mild (uncomplicated), moderate (complicated, doctor) and severe (complicated, doctor) symptomatic infections is set at 83.3%, 15% and 1.7% (Kemmeren 2006; Kwong 2012; redistributing in order to total 100%)
In many reports bacteraemia is highlighted as a possible extra-intestinal complication of salmonellosis (0.03% of laboratory-confirmed cases, Ternhag 2008), although these complicated cases are often considered within the hospitalised proportion of cases (Cressey & Lake 2007; Kemmeren 2006).
The case fatality proportion for symptomatic salmonellosis cases ranged from 0.1% (Kemmeren 2006; Helms 2003) to 0.05% in salmonellosis outbreaks in Austria (Much 2005) and 0.3 for non-typhoid infections in England and Wales (Adak, 2002). These were in line with case fatality proportions observed in cases reported to TESSy between 2009 and 2013 (personal communication).
We chose to estimate the overall case fatality proportion as being within the range 0.050.1% and assumed a different age-group distribution of this risk, based on the age-group distribution of deaths reported to TESSy between 2009 and 2013 (see Table 3). This table is based on all TESSy notified cases from EU Member States except Bulgaria, Latvia and Poland which report only aggregate data, and Italy because the outcome was not reported.
Risk of complications
Reactive arthritis (ReA) and Irritable Bowel Syndrome (IBS) are the most frequent sequelae of salmonellosis reported in the literature (Haagsma 2009; Raybourne 2003). The frequency of other post-infectious complications following salmonellosis is extremely low and these were disregarded in the current study.
Reactive arthritis (ReA)
Many studies reported ReA as sequelae of salmonellosis (Keat 1983; Fendler 2001; Raybourne, 2003). A review of the literature, which included mostly cases of salmonellosis occurring during outbreaks, estimated that 8% (2.315%) of cases are at risk of developing ReA (Raybourne, 2003), although most of these studies have estimated risk based on laboratory-confirmed cases and duration of diarrhoea is highly correlated with the development of ReA (Yu & Thomson, 1994). In order to account for the considerable uncertainty, the risk of developing ReA from all symptomatic cases is set at 1.31% (0.295.43%) (Kemmeren, 2006).
Little is known about the duration of ReA; the average duration is set at between 1.5 months, derived from Hannu et al. (Hannu, 2005) and 222 days (Kemmeren, 2006).
Irritable bowel syndrome (IBS)
In a recent literature review, 8.8% (7.210.4%) of symptomatic salmonellosis cases were considered at risk of developing IBS, irrespective of age and gender; the duration was set to five years (Haagsma, 2010). However, the causality is largely debated and the impact of concurrent factors significant. Therefore, IBS is not considered as part of the salmonellosis outcome tree in our study.
Model input summary
Table 1. Transition probabilities and distributions used in the outcome tree
Health outcome |
Distribution of health states in health outcome |
Transition probability |
Source/assumption |
Symptomatic infection: (Uncomplicated) (Complicated, doctor) (Complicated, hospital) |
83.3% 15% 1.7% |
|
Kemmeren, 2006; Kwong, 2012 |
Fatal cases following symptomatic infection |
|
0.050.1% |
Kemmeren, 2006; Much, 2005; TESSy 2009-2013 |
Reactive arthritis |
|
1.31% (0.29-5.43%) |
Kemmeren, 2006 |
Table 2. Disability weights and duration
Health outcome |
Disability Weight (DW) (Haagsma, 2015) |
Duration |
||
DW |
Label |
In years |
Source |
|
Symptomatic infection (Uncomplicated) (Complicated, doctor) (Complicated, hospital) |
0.073 (0.0610.092) 0.149 (0.120.182) 0.239 (0.2020.285) |
Diarrhoea, mild Diarrhoea, moderate Diarrhoea, severe |
0.015 0.029 0.044 |
Kemmeren, 2006 |
Reactive arthritis |
0.344 (0.30.391) |
Musculoskeletal problems, generalised, moderate |
0.1310.608 |
Hannu, 2002 |
Table 3. Age-group redistribution of CFR (0.050.1%)
Age groups |
% |
0 |
0.69 |
14 |
1.72 |
59 |
1.38 |
1014 |
0.34 |
1519 |
1.03 |
2024 |
0.00 |
2529 |
1.72 |
3034 |
0.34 |
3539 |
1.03 |
4044 |
0.69 |
4549 |
2.07 |
5054 |
3.45 |
5559 |
4.14 |
6064 |
5.17 |
6569 |
9.31 |
7074 |
12.41 |
7579 |
16.55 |
8084 |
18.62 |
>85 |
19.31 |
All ages |
100.00 |
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