Salmonella Virchow

Background: Salmonella enterica subsp. enterica serovar Virchow (antigenic formula 6,7,14:r:1,2) is a serovar of the O:7 (C₁) serogroup. Serovar Virchow was first isolated from a patient with a typhoid-like illness in 1930 by Kaufmann. This serovar has been reported to infect a infant that was transmitted by the household dogs. The ranking of serovar Virchow compared to other Salmonella serovars ranged from 4th to 8th place in Switzerland. Annual incidence rates demonstrated minor change during this period, declining from 0.45 per 100,000 people in 2004 to 0.40 per 100,000 in 2009. Children under 5 years of age showed a seven times higher Salmonella Virchow infection rate compared to those above 5 years. In South-East Asia, Europe, and Oceania, serovar Virchow is consistently found within the top 20 Salmonella serovars. Most often, serovar Virchow infection causes gastrointestinal illness, however, in Israel and other countries including US, human infections occur infrequently but demonstrate a high propensity for invasive manifestations.

NCBI PD link for serovar Virchow: https://www.ncbi.nlm.nih.gov/pathogens/isolates/#(taxgroup_name:%22Salmonella%20enterica%22)%20AND%20computed_types:(%22serotype=Virchow%22)

Genetic characteristics: test

Animal reservoir: Poultry is the main reservoir for serovar Virchow.

Geographical distribution: According to the metadata from NCBI PD, serovar Virchow has been reported in worldwide. In Scotland, serovar Virchow represented almost 25% of confirmed human salmonellosis cases, while in England and Wales, it was the third most common Salmonella serotype in humans, comprising 6% of isolates. However, its prevalence has significantly decreased, now accounting for less than 2% of non-typhoidal Salmonella (NTS) cases in the UK. In Australia, especially Queensland, serovar Virchow has been endemic since the mid-1980s.

Human outbreaks:

Year	Location	Associated source	Number of cases
2017-2023	Multiple countries	Kebab meat containing chicken	210¹
2016	US: multistate	Organic meal & shake powder	33
2012	US: WA	Undetermined	At least 120²
1994	Spain	Infant formula	48
1994	UK	Turkey sandwiches	11³
1968	UK	Spit-roasted chicken	Over 160

¹ Salmonella Virchow ST16 is the outbreak strain. In total, 210 cases have been reported across several countries, including Denmark (2), France (111), Germany (26), Ireland (4), the Netherlands (34), the UK (32), and the US (1).

² Among these cases, 43 were laboratory-confirmed, while 77 others showed symptoms and had a matching exposure history at the restaurant.

³ These cases were confirmed to get infected by Salmonella Virchow, phage type 26.

Border rejections:

Year	Exporting country	Importing country	Associated source	Product category
2021	India	Germany	Dog chews (dried tripes)	Pet food
2020	Poland	Italy	Frozen marinated chicken fillets¹	Poultry meat and poultry meat products

¹ Salmonella Enteritidis, Newport, and Virchow were found.

Recalls: Recalls have been associated with S. Virchow.

Year	Location	Recalled Product	Type
2023	Europe: multi-country¹	Frozen lime leaves²	Fruits and vegetables
2016	US: multistate	Meal replacement³	Other food product / mixed

¹ Ireland, Croatia, and Hungary issued recalls.

² Frozen lime leaves were from Thailand via Netherlands.

³ This recall was caused by a multistate outbreak described above. Garden of Life, LLC extended its recall of RAW Meal Organic Shake & Meal chocolate, original, vanilla, and vanilla chai products on February 12, 2016, adding more lots to the list.

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Salmonella Virchow