Feb 15, 2013 (CIDRAP News) – The US Centers for Disease Control and Prevention (CDC) announced yesterday that it is investigating a Salmonella Heidelberg outbreak simmering since last June that has sickened at least 124 people in 12 states.
Most of the infections have been in Oregon and Washington, and health officials in those two states said yesterday that many of the cases were tied to chicken processed by Foster Farms. The Washington State Department of Health (WSDH) said the outbreak is linked to the company's plants in Washington in California.
The Oregon Health Authority (OHA) said patient reports and lab tests on randomly purchased chicken products have revealed links to Foster Farms chicken. So far no recall has been issued.
Paul Cieslak, MD, of the Oregon Public Health Division, said in the statement that outbreaks are unfortunate but preventable with proper handling of raw poultry products. "Although these cases are linked to a specific brand, there is also some risk of salmonellosis from uncooked poultry products of any brand," he said.
The CDC said it is not releasing the names of the other affected states until investigators determine how their cases are linked to the outbreak. It said public health investigators are using PulseNet, a national molecular subtyping network for identifying foodborne bacteria, to identify other illnesses that may be part of the outbreak.
Fifty-six of the patients are from Washington and 38 are from Oregon, according to the CDC's numbers. The OHA said 43 of its 56 Salmonella Heidelberg infections in 2012, a marked increase from previous years, were caused by a specific Salmonella strain linked to chicken processed by Foster Farms.
The first illness onset was Jun 4, and infections are still being reported, but at lower levels in recent months, which may suggest a "winter lull" in Salmonella infections, the CDC said.
Of 97 cases with information available, 31 patients were hospitalized. No deaths have been reported.
The bulk of investigations by federal, state, and local authorities show that eating chicken was the most likely source of the Salmonella Heidelberg infections. About 81% of sick patients reported that they ate chicken before they became ill. The CDC said the US Department of Agriculture's (USDA) Food Safety and Inspection Service (FSIS) is investigating the source of the outbreak.
Craig Hedberg, PhD, a food safety expert at the University of Minnesota's School of Public Health, told CIDRAP News that it's unusual for the CDC not to name the states in an outbreak, but in the past the agency has been cautious about naming companies involved in outbreaks and might not want to imply, without further investigation, that cases in other states are linked to the same source.
"It is certainly true that some or even most of the cases in other states could have other sources of exposure. Hopefully the ongoing investigation will be able to confirm whether they are all part of the same outbreak, or whether this strain is more widespread than the food network represented by Foster Farms," he said.
Salmonella infections show a distinct seasonality and are more common during summer and early fall, Hedberg said. "The reasons for this are not fully understood, but environmental factors during winter months probably limit the growth and spread of the organisms through contaminated water, feed or environmental surfaces," he said, adding that the organisms can persist in production and food processing systems, which can continue to fuel cases.
Anotherinteresting feature of the outbreak is that there has been no product recall, Hedberg said. Though the USDA monitors contamination levels and companies have reduced them, Salmonella is known to occur on raw chicken and isn't considered an adulterant of the product.
"Because raw chicken may contain Salmonella, consumers are always advised to handle the raw chicken with care and to cook it thoroughly before eating it. These recommendations are being reiterated in the context of this outbreak," he said.
Hedberg said there has been a recent increase in the number of Salmonella outbreaks linked to raw ground beef and ground turkey in which source products were recalled. "It will be interesting to follow this outbreak to see whether new cases continue to be associated with Foster Farms, and if so whether that leads to more aggressive public health interventions," he said.
Feb 14 CDC press release
Feb 14 OHA news release
Feb 14 WSDH news release