Food Safety and Foodborne Illness: (1) Typhoid Fever; (2) Unsafe Cooling
Foodborne illness rarely causes death in people of normal good health; flu-like symptoms (fever, diarrhea, aches and pains, chills) are miserable but usually are self-limiting. Those people with lower resistance, however (elderly, youngsters) may acquire the illness easier and have more serious symptoms. While deaths are not prevalent, other consequences are more serious, affecting the ill customers, as well as the restaurant, its employees, suppliers and the surrounding community. There are also long term impacts: someone recovering from Salmonella, Listeria, norovirus or Hepatitis A virus might shed the organism long after they appear healthy. Other health problems may develop, such as arthritis.
The United States Centers for Disease Control (CDC) compiles data on foodborne illness both to educate the public about illness causes and to point out new and increased food safety risks such as new emerging pathogens or increases in unsafe food handling. For example, in the last decade, the data has pointed to increased risks from contaminated produce as well as risks from unsafe employee personal hygiene. In the latter case, illness caused by bare hand contact prompted a requirement to prohibit bare hand contact with ready to eat foods.
A 2011 article published with the CDC (Emerging Infectious Diseases V. 17, January 2011) estimates that 31 major pathogens (organisms causing illness) acquired in the United States caused 9.4 million episodes of foodborne illness, 55,961 hospitalizations, and 1,351 deaths. Most (58%) illnesses were caused by norovirus (ready to eat food preparation), followed by nontyphoidal Salmonella spp. (11%), Clostridium perfringens (10%), and Campylobacter spp. (9%) – unsafe temperature controls. Leading causes of hospitalization were nontyphoidal Salmonella spp. (35%), norovirus (26%), Campylobacter spp. (15%), and Toxoplasma gondii (8%). Leading causes of death were nontyphoidal Salmonella spp. (28%), T. gondii (24%), Listeria monocytogenes (19%), and norovirus (11%).
The Food Safety News has published two articles (11.14. and 11.15.24) which emphasize the importance of food safety practices. These are summarized below: one article describes a four year episode involving an asymptomatic carrier of typhoid fever; the second article discusses a problem with unsafe cooling practices.
Food Service Worker: Carrier of Typhoid Fever
This blog has repeatedly posted about the importance of monitoring the health of food service workers and the real possibility of healthy workers shedding organisms long after they have recovered from their illness. The case of Mary Mellon (typhoid Mary) is a fascinating story of a New York sanitary engineer who traced typhoid fever illness cases back to this healthy carrier of illness.
Now there is a new case to report from Canada. In a rare occurrence of locally acquired typhoid fever in Canada (most cases of typhoid fever come from developing countries where sewer and water systems may be poor), health officials in Ottawa recently traced an outbreak back to a chronic Salmonella Typhi carrier working as a food handler at a grocery store food counter. The outbreak involved seven confirmed cases from Oct. 2018 to May 2022 and was linked to the asymptomatic carrier through a complicated lengthy detective story. The confirmed cases ranged in age from eight to 50, with six of the seven requiring hospitalizations.
Monitor Employees: It’s vital to train employees about reporting symptoms of illness. Keep records of their agreement to do this. People who have recovered from illness may remain infectious to others (about ten per cent of those recovered may pass the bacteria in their stools or urine for up to three months). While the death rate from typhoid fever is low (<1%), fifteen to twenty percent of cases may experience a recurrence of illness. Two to five per cent of those ill with typhoid may become carriers, passing the bacteria for long periods. Monitor Employee Hygiene: Salmonella typhi is one of many bacteria spread by the fecal-oral route. It is important to regularly monitor safe employee hygiene habits. Bacteria can spread in a number of ways: • Infected employees do not wash their hands and prepare food or drink; require and monitor complete handwashing after any possible contamination but especially after restroom breaks. Consider requiring a second handwashing after employees leave the restroom; • Consumption of ready-to-eat food that has been contaminated by sewage, such as fruit fertilized with night soil, or shellfish from an area contaminated by a sewer outfall. Check deliveries carefully and maintain records of approved suppliers. Shellfish must have evidence of approved harvest areas; maintain these records for at least 90 days after the last date of sale; • Communicate with health- and medical authorities, be certain to notify them when an employee is ill with salmonella typhoid or any of the six reportable illnesses (Norovirus, Nontyphoidal Salmonella, Salmonella Typhi, toxin-producing E. coli, Shigella, and Hepatitis A.) and maintain records when they are approved to return to work; • Communicate with professional consultants about the best health care policies – employees must feel comfortable reporting their illness and not returning to work without clearance, due to economic hardness. In the case of Mary Mellon, she continued to work at different facilities, spreading the bacteria, due to her economic hardship. Clostridum Perfringens – Shredded Chicken – Unsafe Cooling: More than 100 students at a New Zealand university fell ill after eating shredded chicken; laboratory analysis and data collection confirmed the cause as Clostridium perfringens. The time between eating the food and symptoms was, on average, about 11 hours. Both the bacteria and its toxin (formed during its growth) were recovered from the feces of ill students. Symptoms of illness (diarrhea and stomach cramps) usually appear between 6 and 24 hours after eating, in this case 11 hours. This relatively rapid development of symptoms (incubation period) indicates an improperly cooling food. The CDC estimates one million cases annually in the United States. Clostridium perfringens is widely distributed in the environment and is frequently found in the intestines of humans and many domestic and feral animals. Therefore it is already present in good quality products arriving at the restaurant (raw animal foods and produce). It can survive required cooking temperatures by forming spores which protect it from heat or cold. If cooked foods are stored at unsafe temperatures, either on the steam table, cook line or during cooling processes, spores grow in the food and produce toxins. In most instances, the actual cause of poisoning by this organism is temperature abuse of cooked foods. Small numbers of the organism often are present after the food is cooked, due to germination of its spores, which can survive high heat and can multiply rapidly as a result of a fast doubling time, Since the optimal growth temperature for C. perfringens is in the range of 109–117°F (43–47°C) where the generation time may be as short as 8 minutes, it is important to rapidly cool foods through this temperature range. Thorough cooking (140°F) will kill the vegetative cells, but spores may survive. Thus, thorough cooking is only the first step: cooked foods must be held safely to protect against the production of toxins by the spores. In the New Zealand case, the shredded chicken apparently was not cooled rapidly. So, what are the steps for safe cooling of any hot foods? • Hot foods must be rapidly cooled in two steps: first from 135F to below 70F in under 2 hours; second, from 70F to below 41F in under 4 more hours. Why? The important and rapid growth temperature range for Clostridium perfringens lies within that first cooling phase of 135F-70F: it is vital that foods must be rapidly cooled through that range; • Cooling hot foods must be done rapidly by (a) reducing the food into smaller batches; (b) using shallow pans; (c) using blast chillers to remove heat rapidly; and most important (d) using a clock and a calibrated commercial probe thermometer (not a cooking thermometer from home!) to verify the cooling times and temperatures required; • Rapid cooling can be accomplished in a number of unique ways. Some restaurants will wrap the food in a plastic bag or foil wrap and immerse it in ice (do not reuse the ice!) The important point is accurate temperature and time monitoring; • Reheating prepared foods must be done rapidly through the temperature danger zone, to 165F within 2 hours. Again, if food is allowed to sit within that unsafe zone, any spores which survived cooking can produce toxins which can produce illness.