Italian researchers have looked at botulism trends over two decades including a large outbreak in 2020.

Italy has one of the highest botulism rates in Europe with one factor being a strong home canning tradition in the country. From 1986 to September 2022, 406 botulism incidents involving 599 people were laboratory confirmed.

The study described the surveillance system as well as information on botulism cases reported by local health services and those from hospital discharge forms from 2001 to 2020.

Botulism is a rare but life-threatening condition caused by toxins produced by Clostridium botulinum bacteria. In foodborne botulism, symptoms generally begin 18 to 36 hours after eating a contaminated food. However, they can start as soon as six hours after or as long as 10 days later.

Symptoms can include general weakness, dizziness, double-vision, and trouble speaking or swallowing. It paralyzes respiratory muscles so most patients must be placed on life support. Difficulty breathing, weakness of other muscles, abdominal distention and constipation may also occur. People experiencing these problems should seek immediate medical attention.

Major outbreak in 2020
The national surveillance system reported 1,039 suspected cases of botulism from 2001 to 2020. Of these, 452 were laboratory confirmed. Most were male and 255 were 25 to 64 years old. Data showed an increase of cases in this age group in 2012 to 2020, compared with 2001 to 2011.

Of the 452 patients, 412 were foodborne botulism cases, 36 referred to infant botulism and four were wound botulism cases. Fourteen people died. The highest number of suspected cases was 137 in 2013 but the most confirmed cases occurred in 2020 with 74.

The national botulism surveillance system receives an average of 50 reports of suspected cases per year and about half of them are lab confirmed.

A peak in 2004 was because of an outbreak linked to pickled olives which occurred in the province of Campobasso, where 28 cases were involved but only three were lab confirmed.

In 2013, there was a suspected outbreak in Liguria associated with an industrially produced pesto, which was withdrawn from sale by the producer. Hospitals in Genoa reported more than 300 people in less than 24 hours with potential symptoms but none were lab confirmed.

The largest outbreak since 1984 was recorded in 2020. It occurred at a construction site canteen in the province of Palermo. An epidemiological investigation pointed to tuna in a multi-ingredient salad as the source. There were 42 suspected cases and 16 were lab confirmed.

Difference in diagnosis and lab confirmation
The highest incidence rates were reported in the south, particularly Basilicata and Molise. The consumption of improperly home-canned foods is still a concern in rural areas and traditional food preparation is widespread, said scientists.

Botulism cases are most often linked to vegetables preserved in oil, in water or brine as well as meat and fish.

Based on hospital discharge forms, 774 patients were admitted to Italian hospitals in 2001 to 2020. In total, 671 were discharged with a definitive diagnosis of botulism.

At 671, the number of people diagnosed with botulism was significantly higher than the 452 cases confirmed in the lab despite the 774 hospitalizations being lower than the 1,039 suspected infections.

Although the national surveillance system is efficient, there is a need to improve communication and clinical suspicion notification, said researchers.

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