Experts are investigating whether watermelons are linked to an outbreak of salmonella across the UK.
The Health Protection Agency (HPA) said 30 people in England, Wales and Northern Ireland have been infected since the beginning of December - three times higher than is normally expected in a two-month period.
All have a strain of Salmonella Newport infection. Cases of the same strain have been confirmed in Scotland, Ireland and Germany.
The HPA said there had been 26 cases so far confirmed in England, three in Wales, one in Northern Ireland and five in Scotland. The 30 cases in England, Wales and Northern Ireland were among people aged six months to 85-years-old.
One person has died although they had serious underlying health complications, the HPA said. Some 70% of cases have involved women and the East of England is the region most affected.
The HPA said very early indications suggest the cases may be due to people eating watermelon.
In November 2011, as part of a local food survey, the HPA identified Salmonella Newport from a ready-to-eat sliced watermelon. Some people who then became unwell were found to be infected with the same strain.
The HPA has also spoken to 15 affected people and found 10 had eaten watermelon in the three days before they became ill.
It is believed there could be two ways the watermelons have become contaminated with salmonella. Bacteria on the surface of the melon could be transferred to the flesh of the melon while it is being cut up, or may be transferred if melons are stored or washed in contaminated water.
Symptoms include diarrhoea, vomiting, abdominal pain and fever and people usually get better in four to seven days. Some may need antibiotics and complications include blood poisoning or a localised infection.