Final answer:
The CDC provides estimates on foodborne illness morbidity and mortality due to under-reporting, difficulties in identifying specific pathogens, and variation in symptom severity. They use surveillance data to estimate the annual impact, but individual outbreaks, like the 2011 Salmonella case, show the challenges in capturing accurate data.
Step-by-step explanation:
The CDC counts on the annual morbidity and mortality of foodborne illnesses are estimates because of several factors. First, not all cases are reported as many individuals do not seek medical care, and even if they do, not all healthcare providers report these illnesses to health authorities. Moreover, there are a multitude of pathogens that cause foodborne illnesses, and identifying the specific causative agent can be challenging and often goes undetected. Lastly, due to the varying severity of symptoms, some cases may not be linked to foodborne sources without thorough investigation. As a result, the CDC utilizes data collection methods like FoodNet and surveillance reports, including the Morbidity and Mortality Weekly Report (MMWR), to estimate the annual number of foodborne illnesses, hospitalizations, and deaths.
For example, look at the 2011 Salmonella outbreak associated with onions from California. While the CDC was able to trace a specific outbreak and provide concrete data, this instance is only a part of a vast landscape of food-related illnesses that affect the population each year. Due to factors like under-reporting and complexities in identifying pathogens, the CDC has to rely on statistical estimation methods to provide public health information, rather than precise counts.