This paper discusses the traceback method, which has been the basis of some influential papers on first language acquisition. The method sets out to demonstrate that many or even all utterances in a test corpus (usually the last two sessions of recording) can be accounted for with the help of recurrent fixed strings (like What’s that?) or frame-and-slot patterns (like [What’s X?]) that can also be identified in the remaining dataset (i.e., the previous sessions of recording). This is taken as evidence that language learning is much more item-based than previously assumed. In the present paper we sketch the development of the method over the last two decades, and discuss its relation to usage-based theory, as well as the cognitive plausibility of its components, and we highlight both its potential and its limitations.

Since April 2015, whole genome sequencing (WGS) has been the routine test for Salmonella identification, surveillance and outbreak investigation at the national reference laboratory in England and Wales. In May 2015, an outbreak of Salmonella Enteritidis cases was detected using WGS data and investigated. UK cases were interviewed to obtain a food history and links between suppliers were mapped to produce a food chain network for chicken eggs. The association between the food chain network and the phylogeny was explored using a network comparison approach. Food and environmental samples were taken from premises linked to cases and tested for Salmonella. Within the outbreak single nucleotide polymorphism defined cluster, 136 cases were identified in the UK and 18 in Spain. One isolate from a food containing chicken eggs was within the outbreak cluster. There was a significant association between the chicken egg food chain of UK cases and phylogeny of outbreak isolates. This is the first published Salmonella outbreak to be prospectively detected using WGS. This outbreak in the UK was linked with contemporaneous cases in Spain by WGS. We conclude that UK and Spanish cases were exposed to a common source of Salmonella-contaminated chicken eggs.

Produce growers in Kentucky, North Carolina, and Tennessee were surveyed in 2002 to gather information about their decision making in the areas of planting, postharvest handling, marketing, and expected changes. North Carolina has proportionately more respondents with large operations, and Kentucky and Tennessee were more similar and concentrated in smaller farms. Tennessee and Kentucky respondents were less likely to have engaged in activities that were associated with the commercial distribution system. Greater reliance on the commercial distribution system on the part of North Carolina growers is consistent with more produce export activity.

In August 2011, we investigated an outbreak of Escherichia coli O157 in Plymouth, England, utilizing a case-control study and food traceback. Nine cases, eight laboratory-confirmed with E. coli O157 phage type 21/28 verocytotoxin 2 and one epidemiologically linked, had onsets from 30 July 2011 to 15 August 2011. We compared cases (n = 8) with controls (n = 28) of similar age and sex (median age 61 vs. 55 years, females 75% vs. 61%). Cases were 58 times more likely to have eaten crab (88% vs. 11%; odds ratio 58, 95% confidence interval 4-2700). Eight cases consumed crab sourced from the same supplier who was not registered with the local authority. This outbreak pointed to crab as a possible vehicle of E. coli O157 infection. We ensured the withdrawal of crab meat sourced from unregistered suppliers from food venues by 25 August 2011. We also emphasized the importance of only using registered suppliers to the food venues. Since then no further associated cases have been reported.