HPA has confirmed 30 cases in England, Wales and Northern Ireland. Scotland reported five cases; Germany’s Robert Koch Institute and the Republic of Ireland have confirmed 15 cases and 4 cases, respectively. One UK outbreak victim – an individual with serious underlying health complications – has died.
The 30 outbreak victims in England, Wales and Northern Ireland range in age from six months to 85 years; 70% of the case-patients were women, and the outbreak is tilted geographically towards the East of England. Four of Scotland’s five victims were young children, according to the HPA. The outbreak first was detected in early December 2011, and the most recently reported illness was at the end of December.
An Outbreak Control Team is working in the UK to determine the source of the illnesses. A questionnaire has been administered to 15 of the English case-patients so far; 10 of them confirmed having eaten watermelon in the three days prior to becoming ill.
Last November, HPA conducted a local food survey in Preston (Lancashire, England), and recovered Salmonella Newport from a ready-to-eat sliced watermelon fan. Genetic fingerprinting (PFGE) determined at the time that this was a previously unreported strain. The genetic profile of that strain matches the outbreak strain recovered from the four Scottish children who were diagnosed in late December. The same strain also was confirmed in patients from Germany and the Republic of Ireland.
This would not be the first time that Salmonella-contaminated watermelon was the source of an outbreak. In 1954, 17 residents of Upton, Massachusetts (USA) developed salmonellosis after consuming watermelon that was grown in Florida and purchased from a single supermarket in Milford – a neighboring Massachusetts town. Salmonella Miami was found in stool samples from outbreak victims, and from watermelon samples from the homes of two victims. And in 1991, 39 people in the USA became infected with Salmonella Javiana after eating watermelon.
HPA is not yet prepared to state definitively that watermelons were behind this outbreak, and there is no indication so far where the suspect melons may have been grown. Chances are – based on the illness onset dates that have been reported so far – that the offending watermelons will be off the market before they have been identified. Nevertheless, consumers in the affected countries would be wise to avoid purchasing cut watermelon. It is safer to buy an intact melon and sanitize the outside surface before cutting the fruit.