Salmonella infections increasing in the US

Salmonella infections in the US have not decreased during the past 15 years and have instead increased by 10% in recent years, according to a new Vital Signs report released by the US Centers for Disease Control and Prevention.

During the same time period, illnesses from the serious Shiga toxin-producing E. coli O157 have been cut nearly in half and the overall rates of six foodborne infections have been reduced by 23%, the report said.

The Vital Signs report summarises 2010 data from CDC's Foodborne Diseases Active Surveillance Network (FoodNet), which serves as America's report card for food safety by tracking whether nine of the most common infections transmitted through foods are increasing or decreasing.

"Although foodborne infections have decreased by nearly a fourth in the past 15 years, more than 1 million people in this country become ill from Salmonella each year, and accounts for about half of the hospitalisations and deaths among the nine foodborne illnesses CDC tracks through FoodNet," said CDC Director Thomas R Frieden, MD, M.P.H. "Salmonella costs hundreds of millions of dollars in direct medical costs each year. Continued investments are essential to detect, investigate and stop outbreaks promptly in order to protect our food supply."

Salmonella, which is responsible for an estimated $365 million in direct medical costs each year in the US, can be challenging to address because so many different foods like meats, eggs, produce and even processed foods, can become contaminated with it and finding the source can be challenging because it can be introduced in many different ways.

In response to that challenge, the US Food and Drug Administration, which regulates eggs, produce and many processed foods, has developed new rules for the egg industry to follow under its recently expanded regulatory authorities.

"Last summer, FDA began implementing new shell egg safety requirements that should significantly reduce illnesses caused by Salmonella enteritidis in eggs," said FDA Deputy Commissioner for Foods Michael R Taylor. "The recently enacted Food Safety Modernisation Act wisely mandates a comprehensive approach to preventing illnesses from many types of Salmonella and a wide range of other contaminants that can make people sick. The current outbreak of E. coli in Europe demonstrates the importance of the new law, and FDA is committed to implementing the new law as fully as possible within available resources."

In 2010, FoodNet sites, which include about 15% of the American population, reported nearly 20,000 illnesses, 4200 hospitalisations and 68 deaths from nine foodborne infections. Of those, Salmonella caused more than 8200 infections, nearly 2300 hospitalisations and 29 deaths (54% of the total hospitalisations and 43% of the total deaths reported through FoodNet). CDC estimates that there are 29 infections for every lab-confirmed Salmonella infection.

The rate of E. coli O157 cases reported by FoodNet sites was two cases per 100,000 people in 1997 and, by 2010, had decreased to 0.9 cases per 100,000 people. The nearly 50% reduction in E. coli O157 incidence is considered significant when compared to the lack of change in Salmonella incidence. CDC credits the reduction in E. coli to improved detection and investigation of outbreaks through CDC's PulseNet surveillance system, cleaner slaughter methods, testing of ground beef for E. coli, better inspections of ground beef processing plants, regulatory improvements like the prohibition of STEC O157 in ground beef and increased awareness by consumers and restaurant employees of the importance of properly cooking beef. The US Department of Agriculture, the agency that regulates meat, has led these efforts.

"Thanks to our prevention-based approach to food safety, as well as industry and consumer efforts, we have substantially reduced E. coli O157 illnesses," said Elisabeth Hagen, MD, Under Secretary for Food Safety in the US Department of Agriculture. "This report demonstrates that we've made great progress. However, far too many people still get sick from the food they eat, so we have more work to do. That is why we are looking at all options, from farm to table, in order to make food safer and prevent illnesses from E. coli, Salmonella and other harmful pathogens."

The pathogens included in the overall 2010 rate reduction of 23% when compared to 1996-1998 are: campylobacter, E. coli STEC O157, listeria, Salmonella, vibrio and yersinia. Rates of vibrio infection were 115% higher than in 1996-1998, and 39% higher than in 2006-2008. Most vibrio infections are the result of eating raw or undercooked shellfish.

People who want to reduce their risk of foodborne illness should assume raw chicken and other meat carry bacteria that can cause illness and should not allow them to contaminate surfaces and other foods, such as produce. While it's important to wash produce thoroughly, they should never wash meat and poultry. They should also cook chicken, other meats, meat, poultry and eggs thoroughly, avoid consuming unpasteurised milk and juice as well as unpasteurised soft cheese, and make sure shellfish are cooked or treated for safety before eating.