In rare instances, symptoms may come on as early as a half hour after eating the contaminated food but they typically do not develop for several days or weeks. Symptoms of viral or parasitic illnesses may not appear for several weeks after exposure. Symptoms usually last only a day or two, but in some cases can persist a week to 10 days. For most healthy people, foodborne illnesses are neither long-lasting nor life-threatening. However, they can be severe in the very young, the very old, and people with certain diseases and conditions.
These conditions include:
- liver disease, either from excessive alcohol use, viral hepatitis, or other causes hemochromatosis, an iron disorder
- stomach problems, including previous stomach surgery and low stomach acid (for example, from antacid use)
- immune disorders, including HIV infection
- long-term steroid use, as for asthma and arthritis.
When symptoms are severe, the victim should see a doctor or get emergency help. This is especially important for those who are most vulnerable. For mild cases of foodborne illness, the individual should drink plenty of liquids to replace fluids lost through vomiting and diarrhea.