It is part of a gradual increase in infections since 2009 in European Union/European Economic Area (EU/EEA), said the European Food Safety Authority (EFSA) and the European Centre for Disease Prevention and Control (ECDC).
However, the agencies admitted that they do not know yet if cases are linked or the source of the problem but the increase across several countries suggests a common exposure.
EFSA and ECDC recommended a multi-sectorial investigation to understand and assess the risk associated with the increasing trend of S. Mikawasima infections.
Microbiological investigations through whole genome sequencing should provide further evidence to find a common source of infection.
UK case increase
From 2007 to 2012, 671 human cases of S. Mikawasima were reported from EU and EEA countries to the European Surveillance System (TESSy).
Analysis of the S. Mikawasima cases reported for Q1 and Q2 2013 showed a significant peak in May (11 cases) compared to the historical average of 3.6 cases, largely due to reports by the UK (9/11 cases).
The UK (75 cases), Denmark (11), Germany (9) and Sweden (6) all reported unusual increases at the national level from September – November 2013.
PFGE-typing of a subset of human isolates from UK and Denmark yielded indistinguishable profiles, suggesting a link between the cases but the low discriminatory power does not allow firm conclusions to be drawn, said the agencies.
History of strain
An Urgent Inquiry (UI) was posted by Denmark in 2012 on the Epidemic Intelligence Information System for Food- and Waterborne Disease and Zoonoses (EPIS-FWD), reporting a possible outbreak which Norway responded to, also noting a marked increase in cases.
During 2004—2012 (including some data from 2013), 120 isolates of the serovar were reported from food, feed and animals.
There were some mostly single isolations from food sources, such as vegetables, sausages meat and nuts.
One outbreak of S. Mikawasima causing human gastroenteritis caused nine cases in October 1992 in the UK with epidemiological investigations identifying doner kebabs as a probable source.
Rapid Alert System for Food and Feed (RASFF) database reports one notification in 2005 for S. Mikawasima presence in frozen squid tentacles from India, said the agencies report.