Foodborne botulism is a serious illness caused by consuming food contaminated with botulinum toxin, a dangerous substance that affects the nervous system. This disease is extremely uncommon; for instance, in 2019, there were only 21 documented cases of foodborne botulism in the United States, according to the U.S. Centers for Disease Control and Prevention (CDC).

While botulism can be treated, early detection is crucial. The toxin can cause muscle paralysis, difficulty in breathing, and in severe instances, death as it spreads through the body.

Recognizing the symptoms of botulism could save lives. Here’s what you need to know.

What exactly is Clostridium botulinum?

Clostridium botulinum is a bacterium that generates the botulinum toxin, responsible for botulism, according to Dr. Daniel Kuritzkes, Chief of the Division of Infectious Diseases at Brigham and Women’s Hospital. This bacterium can be found widely in nature, often lurking on the surfaces of fruits and vegetables, as advised by the U.S. Department of Agriculture’s Food Safety and Inspection Service.

Fortunately, contact with Clostridia seldom leads to illness. The bacteria, including C. botulinum and occasionally related species like C. butyricum and C. baratii, can produce harmful spores only under specific conditions. They thrive in low-oxygen environments and low-acid, low-sugar, or low-salt settings, according to the CDC.

Where can Clostridium botulinum typically be found?

Home-canned and preserved foods are particularly prone to Clostridia growth, says Shonna McBride, an associate professor specializing in microbiology and immunology at Emory University School of Medicine.

If the spores of Clostridium botulinum are present on the fruits or vegetables you’re trying to preserve and your canning tools are not properly sterilized, you risk enabling the bacteria to create toxins, explains McBride.

Currently, cases of foodborne botulism linked to commercially canned products are exceedingly rare, according to Kuritzkes. This is mainly due to frequent inspections in food processing facilities focusing on cleanliness and sterilization standards.

Since botulism toxin cannot be detected by sight, smell, or taste, it can be hard to know if food is contaminated, as noted by the CDC. However, one indication of potential contamination is a bulging can, McBride adds. As the bacteria grow, they can produce gas, resulting in significant swelling of the can.

What are the symptoms of foodborne botulism?

“Even a tiny amount of botulism toxin can cause severe effects,” warns Kuritzkes. The toxin is absorbed through the digestive system and targets the nerves, causing muscle paralysis due to the loss of nerve communication, explains McBride.

Dr. Scott A. Weisenberg, an infectious disease expert and medical director at NYU Langone Health’s Travel Medicine Program, states that key signs of foodborne botulism include trouble swallowing and speaking, vision changes, general muscle weakness, and difficulty breathing. Symptoms can manifest as early as four hours after ingestion but typically appear within 12 to 36 hours, according to the World Health Organization.

Is it possible to fully recover from botulism?

Without treatment, botulism can cause total respiratory failure and may lead to death, according to Kuritzkes. The World Health Organization records a fatality rate of 5% to 10% for botulism cases. However, early intervention can lead to complete recovery, making it essential to seek medical help if you experience botulism-like symptoms.

The botulism antitoxin neutralizes the toxin, preventing further nerve damage but does not repair any harm already done. In severe instances, patients may require intubation to assist with breathing. While the toxin eventually clears from the body, symptoms may linger for several months, says McBride.

While it’s important to note that botulism is very rare, taking safe food handling and storage precautions can reduce your risk, advises Weisenberg, especially for those preparing canned foods at home.