Preserving Season Is in Full Swing: NPHC Warns of the Hidden Risk of Botulism
As summer comes to an end, the season of harvesting and preserving food gets underway. Vegetables and mushrooms are preserved, and meat products are prepared for storage. Specialists from the National Public Health Centre (NPHC) remind the public that botulinum toxin can develop in improperly prepared or stored preserved foods, causing botulism – a rare but serious disease. That is why it is essential to follow food preparation, preservation and storage safety rules.
How does botulism occur?
Botulism occurs when a person is poisoned by a toxin produced by bacteria under favourable conditions. These bacteria thrive in environments with little or no oxygen, moisture and low acidity. Such conditions can develop in canned foods, jars or plastic packaging. If food is prepared or stored improperly and bacteria contaminate it, botulinum toxin may begin to form.
“Botulinum toxin cannot be reliably detected simply by looking at the food. Contaminated food may look completely normal and show no obvious signs of spoilage. However, gas produced as the bacteria multiply can cause the lid of a jar to bulge. This is a warning sign that the food may be unsafe. Such preserved foods must not be eaten,” warns Aušra Valaikienė, adviser at NPHC Communicable Disease Management Division, currently acting as Head of the Division.
Everyone is susceptible to botulinum toxin. If the toxin enters the body, anyone can develop the disease. However, not everyone who eats the same contaminated food necessarily becomes ill because the toxin may not be evenly distributed throughout the food. As a result, one person may consume a larger dose while another may consume a smaller amount that is insufficient to cause illness.
Early signs of botulism
The first symptoms of botulism usually appear 12–36 hours after eating contaminated food. Early symptoms may include severe fatigue, weakness and dizziness. Vision problems may develop later: a person may experience blurred vision or see double. Other symptoms include dry mouth and difficulty swallowing or speaking. Gastrointestinal symptoms may also occur, including nausea, vomiting, diarrhoea, constipation or abdominal bloating. As the disease progresses, breathing difficulties may develop, posing a serious threat to life.
“Botulism symptoms should not be ignored. If characteristic symptoms occur — particularly problems with vision, swallowing or speech, or increasing muscle weakness — it is essential to seek medical attention without delay. Prompt medical care is extremely important,” emphasises Aušra Valaikienė.
Having had botulism does not provide immunity, so a person can develop the disease again. Botulism cannot be transmitted from an infected person to other people.
Botulism is rare
Cases of botulism are reported worldwide. In Lithuania, one case of botulism was reported each year from 2018 to 2020. No cases were recorded in 2021 or 2022, while two cases were reported in 2023. No cases were recorded in 2024, and two cases were reported in 2025. Thus, botulism remains a rare disease in Lithuania.
In Europe, botulism is also a relatively rare but serious disease. Even with modern treatment, the case-fatality rate is 5–10%; without treatment, around half of patients die. According to the European Centre for Disease Prevention and Control, around 200 cases of botulism are reported in the European Union each year. Most cases are foodborne. Outbreaks in Europe have been associated with a variety of foods, including meat products, fish, and vegetables preserved or stored in oil. A significant number of outbreaks are linked to food that has been improperly prepared or preserved at home.
How can botulism be prevented?
There is no vaccine against botulism, so one of the most important preventive measures is safe food preparation and proper storage:
- Prepare food with clean hands.
- Use a separate cutting board and utensils for raw meat, and cook meat thoroughly.
- Wash vegetables and mushrooms thoroughly before preserving them.
- When preserving meat, mushrooms and vegetables, use acid, salt or sugar, as these help inhibit bacterial growth.
- Use containers suitable for food preservation and ensure that the preservation process destroys bacteria and their spores. Follow the specified heat-treatment time, temperature and pressure requirements.
- Store preserved foods in a cool place.
- Do not eat preserved food if the lid is bulging or the contents look suspicious.
- Buy preserved foods only from reputable manufacturers.
Last updated: 11-09-2026
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