CDC foodborne illness snapshot highlights heavy burden, successes

Salmonella infection was the leading cause of death, killing 238 people, trailed by Campylobacter spp (197), norovirus (174), invasive L monocytogenes (172), STEC (66), T gondii (44), and C perfringens (41).

Of Salmonella-related illnesses, 23% were estimated to be caused by serotype Enteritidis, followed by Newport (14%), Typhimurium (11%), I 4,[5],12:i:- (7%), and Javiana (7%). More STEC illnesses were caused by all non-O157 serogroups (76%) than by STEC O157 (24%). L monocytogenes caused 920 non–pregnancy-associated and 148 (74 mothers, 74 infants) pregnancy-related hospitalizations and 166 nonpregnancy-associated deaths and 6 pregnancy-linked deaths, all among infants.

Widespread use of more-sensitive tests

These statistics reflect increases in case counts since 2011 for Campylobacter (845,000 in 2011), nontyphoidal Salmonella (1 million), STEC O157 (63,200), and non-O157 STEC serogroups (113,000 vs 271,000 in 2019). The authors largely attributed the changes to the widespread use of CIDTs, which are more sensitive and much faster than culture, advances in analytical methods, and, for some pathogens, a new approach to adjusting for underdiagnosis.

"Diagnosing infections caused by non-O157 STEC serogroups was especially challenging before the introduction of CIDTs," they wrote. "Although serogroup O157 causes most STEC-induced hospitalizations and deaths, non-O157 serogroups cause 3-fold more illnesses than O157 and cause a substantial number of hospitalizations and deaths."

But the 2019 numbers also represent a decline in T gondii hospitalizations (848, down from 8,889 in 2011) and deaths (44, down from roughly 656 in 2011), which Hedberg attributes to the advent of antiretroviral therapies for people with HIV. 

"People with HIV infections no longer necessarily develop AIDS, because the infection is controlled, so they don't develop the opportunistic infections that go along with AIDS," he said.

"One of the things that would be a concern, given where we are on a national and global level, if we reduce the amount of effort we put into maintaining control and providing therapy to people who are infected with HIV, the consequences are that we'll see a resurgence in things like toxoplasmosis and other opportunistic infections that have been largely been suppressed but haven't gone away," he added.

Opportunities and vulnerabilities 

Hedberg also noted a slight decline in outbreak-associated C perfringens infections in the 2019 report, from 966,000 to 889,000. "That is potentially a signal that we're doing a better job at controlling the conditions that lead to Clostridium perfringens in our commercial food service operations," he said.

The estimates in the report "can be used as a platform to attribute illnesses to specific food categories and also to estimate societal and economic costs of foodborne illness and the numbers of persons who develop disease sequelae," the study authors concluded. "When considered with other information, such as major food sources of illnesses, population groups affected, and costs of making foods safer, the estimates can be used to prioritize food safety interventions."

Hedberg said efforts to reduce foodborne illnesses need to continue on all levels. He called for, among other actions, the reduction of relevant pathogens from organisms in animal populations and the environment to lower the rate of human infections from, for example, E coli O157 from leafy greens grown near cattle feedlots.

"And throughout the food system, we need to explore what are the opportunities we have to control or reduce the risk of that going forward," he said. "So that extends into commercial kitchens and restaurants. We need to be continuously looking at where are the opportunities to control transmission in restaurant settings? Where are the vulnerabilities that might amplify contamination in those settings, and also in people's homes?"