Analysis of case interviews on risk factors from the ongoing outbreak identified consumption of frozen mixed berries (redcurrant, blackberries, raspberries, blueberries) as the potential vehicle of infection.
The hypothesis that they could be implicated is strongly supported by the detection of Hepatitis A (HAV) virus in a sample of frozen mixed berries.
Seven sequences of HAV genotype 1A isolated from cases in different countries (the Netherlands, Germany and Italy) and in different laboratories showed a 100% similarity.
Common food identified
The preliminary epidemiological investigation in the provinces of Trento and Bolzano showed that the common food consumed by different cases was mixed berries or food containing mixed berries (cakes).
Moreover, the hypothesis was strongly supported by the results of an epidemiological investigation conducted in a family cluster in Veneto region.
Part of the mixed berries (redcurrant, blackberries, raspberries, blueberries) that the cases indicated to have eaten within the period of time compatible with the onset of clinical symptoms were still available and were sampled. The analysis for HAV detection in the sample of mixed berries provided positive results.
Comparison of information from the tracing-back of positive frozen mixed berries with information obtained through the purchase history is ongoing.
The analysis said the case-control study is currently ongoing and the results of this investigation will provide an opportunity to support the hypothesis of the likely source of infection.
This, with the molecular sequencing information will provide a picture of the genotypes in the outbreak to be compared to those circulating in the previous years in Italy and those circulating in other countries.
More samples of berries were collected once they were identified as potential risk factors, and two sampled berries in Trento were found positive for HAV.
Environmental investigations have been done on the mixed frozen berries suppliers of raw material in six different countries. Results on samples collected are pending at the time of the present rapid communication.
The surveillance on the frozen mixed berries and other food items potentially carrying the HAV (vegetables, seafood, and other food reported as potential risk factors), has been intensified, to provide a picture of the distribution of the contaminated items and the risk of exposure.
Despite the effort made in the detection of positive food consignments and their recall, more cases are expected, due to the long incubation period of HAV (28–30 days; range: 15–50 days), the notification delay, and the long shelf life that frozen berries have.
Source: Eurosurveillance, Volume 18, Issue 27, 4 July 2013
“Ongoing outbreak of hepatitis A in Italy: preliminary report as of 31 May 2013”
authors: C Rizzo, V Alfonsi, R Bruni, L Busani, A R Ciccaglione, D De Medici, S Di Pasquale, M Equestre, M Escher, M C Montaño-Remacha, G Scavia, S Taffon, V Carraro, S Franchini, B Natter, M Augschiller, M E Tosti, the Central Task Force on Hepatitis A