Ongoing surveillance identified in February that infections from some of the previously rare outbreak strains again exceeded the number of infections expected to be reported to PulseNet during this time of year.

As of 7 April, a total of 524 persons infected with seven outbreak strains of Salmonella Heidelberg have been reported from 25 states and Puerto Rico, since 1 March 2013.

A total of 37 per cent of those people who had been affected had to receive hospital treatment but according to the Centers for Disease Control and Prevention no deaths have been reported.

Most of the ill people 76 per cent have been reported from California.

Since the last update on 3 March, a total of 43 new ill persons have been reported from five states: Arizona (2), California (34), Michigan (1), Oregon (3), Texas (2), and Washington (1).

Among 518 persons for whom information is available, illness onset dates range from 1 March 2013 to 18 March 2014.

Those who have become sick range in age from less than one year to 93 years, with a median age of 18 years.

Fifty-one per cent of those ill are male.

Among 437 persons with available information, 162 (37 per cent) reported receiving hospital treatment.

Thirteen per cent of those sick have developed blood infections as a result of their illness.

Typically, approximately five per cent of people ill with Salmonella infections develop blood infections.

Illnesses that began after 8 March 2014, might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of two to four weeks.

Epidemiologic, laboratory, and traceback investigations conducted by local, state, and federal officials indicate that consumption of Foster Farms brand chicken is the likely source of this outbreak of Salmonella Heidelberg infections.

The CDC said the outbreak strains of Salmonella Heidelberg are resistant to several commonly prescribed antibiotics. Although these antibiotics are not typically used to treat Salmonella bloodstream infections or other severe Salmonella infections, antibiotic resistance can be associated with increased risk of hospitalization in infected individuals.

The CDC added that it is not unusual for raw poultry from any producer to have Salmonella bacteria. CDC and USDA-FSIS recommend consumers follow food safety tips to prevent Salmonella infection from raw poultry.

A statement from Foster Farms said: “Foster Farms is committed to leadership in food safety and producing the safest chicken on the West Coast.

“Since October 2013, Foster Farms has developed a multiple-hurdle approach to reduce or eliminate Salmonella at each stage of production – from screening breeder flocks before entering the Foster Farms system, to farms where the birds are raised, to the plants where the chicken is processed as a whole bird and when it is cut into parts.

“As a result, the company has steadily reduced the prevalence of Salmonella at the parts level toward a goal of less than 10 per cent – well below the USDA-measured industry benchmark of 25 per cent.

“Foster Farms reminds consumers to practice proper food handling and cooking practices at all times, and especially during the warmer months. According to the CDC, ‘Salmonella illness is more common in the summer. Warmer weather gives bacteria more opportunity to contaminate food’."