A 60-year-old diabetic woman in Zhejiang, China, recently fell into a coma after eating refrigerated watermelon that had been stored for several days. The culprit: Listeria monocytogenes—a lethal bacterium that thrives in cold temperatures and can survive up to one year at minus 20 degrees Celsius.
The case, reported by Chinese media, serves as a stark warning: refrigeration is not a foolproof shield against foodborne pathogens.
A Mysterious Fever Turns Critical
The woman, identified only by the surname Cen, initially developed a high fever that her family mistook for a common cold. Her temperature soon spiked past 40 degrees Celsius, accompanied by dizziness and unsteady walking. Rushed to a local hospital, she was quickly transferred to Zhejiang Provincial People’s Hospital as her condition deteriorated.
Upon arrival, Cen was still burning with fever. She developed impaired eye movement and facial nerve paralysis before slipping into unconsciousness. Doctors immediately placed her in the intensive care unit.
Dr. Cai Xiaofeng, a neurologist at the hospital, suspected the central nervous system was under attack. Through cranial MRI, lumbar puncture, and advanced genetic sequencing of cerebrospinal fluid, the diagnosis was confirmed: Listeria monocytogenes had caused a severe brain abscess.
The Source: A Few Slices of Old Watermelon
Investigating Cen’s recent eating habits, doctors discovered she had consumed pieces of watermelon that had sat in her refrigerator for several days. Dr. Cai explained that the watermelon had likely become heavily contaminated with Listeria during storage. Once ingested, the bacteria travelled through the gastrointestinal lining, entered the bloodstream, and invaded the central nervous system.
While most Listeria infections manifest as meningitis, developing into a brain abscess is rare. Fortunately, after targeted antibiotic treatment, Cen regained consciousness and has been moved to a general ward for continued recovery.
Why Refrigeration Offers No Protection
Dr. Guo Shunyuan, chief neurologist at the hospital, explained that Listeria is an anaerobic bacterium that spreads primarily through food. It is widespread in nature and can contaminate meat, eggs, poultry, seafood, dairy products, and vegetables.
What makes Listeria particularly dangerous is its resilience to cold. It can grow slowly at temperatures between 0°C and 4°C and survive for up to a year at minus 20°C. This earns it the chilling nickname—the “fridge killer.” Any refrigerated leftovers, cold cuts, raw foods, or pre-prepared salads can become carriers and breeding grounds for the bacteria.
Symptoms typically appear three to seven days after infection. Mild cases resemble flu, but severe infections can cause fever, intense headache, nausea, vomiting, diarrhoea, and potentially lead to sepsis, meningitis, or brain abscesses. Cen’s pre-existing diabetes weakened her immune system, making her more vulnerable.
Protecting Yourself from the Fridge Killer
Dr. Guo recommends four key strategies to prevent Listeria infection:
- Avoid high-risk foods: Skip unpasteurised dairy products and foods that have been refrigerated for extended periods, such as leftovers.
- Cook food thoroughly: Ensure meat, seafood, and other perishables are cooked to piping hot temperatures.
- Maintain hygiene: Wash hands thoroughly, and keep raw and cooked foods separate to prevent cross-contamination.
- Clean the refrigerator regularly: Remove expired and spoiled items promptly. Seek medical attention immediately if symptoms of Listeria infection appear.
Who Is Most at Risk?
According to Hong Kong’s Centre for Health Protection, Listeria can be found in contaminated vegetables, raw meat, unpasteurised milk, soft cheeses, and deli meats. Pregnant women, newborns, the elderly, and immunocompromised individuals face the highest risk.
Pregnant women often show only mild symptoms but can pass the bacteria to their foetus, leading to miscarriage, stillbirth, premature birth, or life-threatening infections in newborns such as sepsis and meningitis.
Seven Practical Prevention Tips from Food Safety Authorities
Hong Kong’s Centre for Food Safety offers these actionable steps:
- Wash vegetables thoroughly and cook all food completely (standard cooking temperatures kill Listeria).
- Clean hands, knives, and chopping boards after handling raw foods.
- Store cooked food on upper shelves and raw food on lower shelves in the refrigerator.
- Eat perishable foods soon after purchase; avoid hoarding.
- Reheat leftovers until steaming hot throughout before eating.
- Inspect food packaging for damage before buying.
- Adhere strictly to expiry dates, especially for refrigerated ready-to-eat foods with long shelf lives (over five days).
This case underscores a critical lesson: cold storage is not a guarantee of safety. Proper food handling, thorough cooking, and regular refrigerator maintenance are essential defences against a bacterium that refuses to be frozen out.