Almost 350 confirmed and 50 more possible Salmonella infections have been recorded across Europe and in the United Kingdom linked to melons. Some patients live in the United States.

Between mid-March and early July, 348 people fell ill due to Salmonella Braenderup and 68 needed hospital treatment but none have died. Four people were sick in the United States and two in Canada.

In late June, the U.S. Centers for Disease Control and Prevention (CDC) looked into three illnesses related genetically by whole genome sequencing, but didn’t find a link to those sick after eating melons in the UK. One ill person travelled outside the U.S. before they were sick but not to Europe and didn’t report eating melons. The other two sick people didn’t have food histories available and didn’t report traveling.

The UK is the most affected country with 102 confirmed infections while Sweden, Belgium and Germany all have 46. Denmark has 37 cases, Netherlands has 34, Switzerland has 18 while Austria, Czech Republic, Finland, France, Ireland, Luxembourg and Norway have single figure patient numbers. Of the UK total, 90 live in England, eight in Scotland and two each in Wales and Northern Ireland. Austria has seven probable cases, Belgium has eight, Germany has 29 and Ireland has two.

The International Food Safety Authorities Network (INFOSAN) has been following the multi-country outbreak since May 10.

Outbreak strain finding
Small melons, in particular Galia, are the possible vehicle of infection. Salmonella Braenderup matching the outbreak strain was isolated in the UK in two of 200 sampled imported Galia melons from one batch from Honduras, and in Austria from a pooled sample of melons with unknown origin, including Galia, in April.

The two UK positives were sampled on June 1 at a British wholesaler and were imported by vessel before being distributed to 10 businesses. Melons from Honduras were sampled by authorities in Luxembourg, Finland and Ireland but tested negative for Salmonella.

However, patients were detected from March 2021, before the positive batch was harvested and packed on April 21 indicating contaminated food vehicles had been circulating earlier. The batch arrived in the UK on May 19 and could only explain six cases.

Investigations initially looked at the supply chain of galia, cantaloupe and honeydew melons from Honduras, Costa Rica and Brazil before the latter country was ruled out.

One isolate matching the outbreak strain was detected in Finland from a boot swab sample in a hobby henhouse wher hens had been fed melon rinds by their owner, who also tested positive for this strain.

Further investigation is needed to identify the exact point and contributing factors of contamination along the production chain, including transportation, said the European Centre for Disease Prevention and Control (ECDC).

Investigation in Honduras
The Honduran producer finished harvesting melons in April 2021 and they are no longer on the market. No exports from Honduras are planned until the new season starts in December.

Galia melons from Honduras were sent to the EU via the Netherlands and redistributed to member states. They were exported mainly to the EU but also to the UK, U.S. and Japan.

During the 2021 season, 4,000 samples were collected at different points of the production and packing chain and no positives were reported for any pathogens routinely monitored, including Salmonella.

Reports peaked in April and May when 198 and 128 cases were reported respectively. The patient age range is from below one to 101 years old and women have been more affected then men.

Belgium, the Netherlands, and Norway have recorded outbreaks or cases in nursing homes.

Out of 197 confirmed cases with information available, almost two thirds reported having consumed any type of melons seven days prior to illness onset. The majority of melons eaten by patients, including galia, charentais, honeydew, and cantaloupe, were traced back to the Honduran producer. Galia melons were consumed by nearly half of 140 cases.