2 February 2012
The Health Protection Agency (HPA) is investigating an outbreak of a strain of Salmonella Newport infection among 30 people in England, Wales and Northern Ireland since the beginning of December 2011. Cases of illness caused by the same strain have been confirmed in Scotland, Ireland and Germany.
The figures compare to 10, 12, and 11 cases over the same period in 2008, 2009 and 2010 respectively. Around 200 cases of Salmonella Newport are reported in England, Wales and Northern Ireland each year.
Infection with Salmonella Newport causes a similar illness to other forms of Salmonella infection and symptoms include diarrhoea, vomiting, abdominal pain and fever. The 30 cases in England, Wales and Northern Ireland ranged in age from six months to 85 years. One person has died although they had serious underlying health complications. Seventy per cent of cases were women with the East of England having more cases than other regions.
Dr Bob Adak, head of the gastrointestinal diseases department at the HPA said: “Although it’s too soon to say with certainty what the likely cause of infection is, early indications suggest that a number of people became unwell after eating watermelon. This has also been noted in the cases in Scotland and Germany although further investigation is ongoing.
“It’s important to remember the risk of becoming unwell after eating watermelon is very low. These cases only represent a very small proportion of total consumption. It is always advisable to wash fruits and vegetables – including watermelon – before consumption to reduce the risk of possible illness.
“Colleagues from the Food Standards Agency are part of the outbreak control team and they are working with us to identify the source of this outbreak.”
Salmonella Newport has been found in many different foods in previous UK outbreaks - the largest one was in 2004 and was associated with the consumption of lettuce at restaurants and takeaways.
1. Confirmed cases:
• England - 26
• Wales - 3
• Northern Ireland - 1
• Scotland - 5
• Republic of Ireland - 4
• Germany – 15
2. About Salmonella Newport:
Q. What is Salmonella Newport?
There are over 2,500 different types of Salmonella species and Salmonella Newport causes a similar illness to other forms of Salmonella infection.
As with most Salmonella strains it affects the stomach and intestines. Most cases resolve within four to seven days but some people may need a course of antibiotics. Complications can include septicaemia (blood poisoning) or a localised infection e.g. septic arthritis.
Q. How many cases of this kind of Salmonella do you normally see in England, Wales and Northern Ireland each year?
Previous figures for the number of cases of the outbreak strain of Salmonella Newport that the HPA have recorded in previous years are:
Ave: 197 (5 year average)
Q. What has caused this outbreak?
Very early indications suggest that the recent increase in cases may be linked to the consumption of watermelon. In November 2011, as part of a local food survey, the HPA identified Salmonella Newport from a ready-to-eat sliced watermelon.
Subsequently a number of people who became unwell were found to be infected with the same strain of Salmonella Newport identified in the survey watermelon sample. In addition 10 of the 15 cases who have been followed up by telephone interview reported eating watermelon in the three days prior to the onset of their symptoms.
The HPA is liaising with the Food Standards Agency (FSA) and colleagues in the Devolved administrations to investigate this outbreak. The FSA work with the food industry to ensure that our food is safe to eat and they will take any necessary actions to remove unsafe food from the supply chain.
Q. How would the Salmonella infection contaminate the infected food?
There are two possible routes of infection. Firstly, the surface of the melons could have been contaminated with Salmonella bacteria and this may have transferred onto the flesh of the melon during the cutting process. Secondly, if the melons were stored or washed in contaminated water, the Salmonella bacteria could have got into the flesh of the melon through the cut stem.
Q: Have there been previous outbreaks of Salmonella Newport in Europe?
Yes, there was an outbreak in 2011 in Germany and the Netherlands but this strain was different from that which we are currently seeing and the cause was bean sprouts.
It is not uncommon that the source of outbreaks is not identified because many foods contain multiple ingredients and identifying which is the contaminated component is very difficult.
There have been outbreaks in different parts of the world which have been caused by foods such as alfalfa sprouts.
Q: What does the HPA do to investigate outbreaks of Salmonella?
If there is an outbreak then the first evidence will be an increase in the number of samples that come from GP surgeries for testing.
The HPA would then have to establish whether this was an outbreak or whether there could be any other explanation for the increase in cases.
• Are the cases coming from abroad?
• Have the samples been misclassified in the lab?
• Is there a lab backlog of samples so it appears there is a peak when there is not?
If it still appears there is an outbreak then structured food questionnaires are sent to the affected patients. These would include descriptive data including personal details of the patients, clinical histories, household details, what food they had eaten in the three days before becoming ill and where it was bought, their food preferences and travel histories.
After this a number of patients would receive follow up phone calls to see if there are any links between them. To ensure objectivity there will be a group of patients who are unwell and a group who are not – the controls. Based on the evidence from the questionnaires and the telephone interviews if it appears the outbreak is foodborne then an Outbreak Control Team is established. The HPA would then work with other organisations to prevent other people becoming unwell including the Food Standards Agency and Environmental Health.
For more information on Salmonella, please visit our website:
3. The Health Protection Agency is an independent UK organisation that was set up by the government in 2003 to protect the public from threats to their health from infectious diseases and environmental hazards. In April 2013, subject to the usual approvals procedures for establishing new bodies, the Health Protection Agency will become part of a new organisation called Public Health England, an executive agency of the Department of Health. To find out more, visit our website: www.hpa.org.uk or follow us on Twitter @HPAuk.
4. For more information please contact the national HPA press office at Colindale on 0208 327 7901 or email firstname.lastname@example.org. Out of hours the duty press officer can be contacted on 0208 200 4400.
Last reviewed: 1 May 2012