What type of illness is primarily caused by E. coli?

E. coli, especially certain strains such as E. coli O157:H7, is primarily associated with gastrointestinal illness. This bacterium can cause severe abdominal cramps, diarrhea (often bloody), vomiting, and occasionally fever. The gastrointestinal system is directly affected due to the bacterium's ability to produce toxins that disrupt normal intestinal function, leading to these symptoms.

In contrast, other types of illnesses listed do not typically involve E. coli. For instance, respiratory illnesses are generally caused by viruses or bacteria specifically targeting the respiratory system, skin infections usually result from direct skin contact with pathogens like Staphylococcus or Streptococcus, and nervous system infections are typically associated with bacteria like Neisseria meningitidis or viruses such as those that cause viral meningitis. Therefore, the connection between E. coli and gastrointestinal illness is well established, making that choice the most accurate in this context.