food poisoning

Introduction

illness after eating food may be caused by either:
- toxins in the food produced by bacterial contamination of the food
  - symptoms tend to occur very soon after ingestion eg. Staph, E.coli toxins, botulism (or may take days)
- bacterial or viral contamination of the food resulting in infection
  - many foods stored in the “danger zone” of 5-60degC for some hours may become tainted with excessive growths of pathogenic bacteria
    - food that needs to be chilled should be kept below 5degC, and hot food should be maintained and served above 60degC
  - meats should be cooked to the minimum recommended temperatures for the type of meat
  - boiling suspect water is a good way to eliminate hepatitis A and giardia
  - unlike heating, freezing foods does not usually kill pathogens it just slows their growth substantially
  - avoid eggs that are dirty or cracked
  - avoid eating foods past their expiry date
  - unpasteurised milk causes 840x more illnesses and 45x more hospitalisations from illness than pasteurised milk - esp. Campylobacter, Cryptosporidium, E. coli, Listeria, Brucella, and Salmonella (and potentially viruses including avian influenza) ¹⁾.
  - symptoms are generally delayed by days eg. Salmonella, hepatitis A, giardiasis
  - symptoms may be delayed by months eg. Listeria monocytogenes / Listeriosis, parasites
- allergy reactions
  - type 1 HS reactions such as:
    - eggs in infants
    - peanuts, cashews, walnuts
    - shellfish
    - quinine (rare severe kidney injury via immune-mediated thrombotic microangiopathy (TMA))
    - tick-induced mammalian red meat allergy (MMA) / alpha-gal syndrome
- food intolerances
  - inability to absorb the amount of sugars, etc
  - coeliac disease
  - malabsorption
- organic disease and other causes of food “intolerance”

causes of food poisoning

Norovirus was the primary contaminant in fruits and vegetables during foodborne illness outbreaks in the European Union (EU) and the United States (US) during 2004-12, followed by bacterial pathogens - three bacterial pathogens, Listeria monocytogenes, Escherichia coli (mainly Shiga toxin-producing E. coli (STEC) ), and Salmonella enterica, were responsible for 82% of hospitalizations and deaths due to foodborne illnesses in the US during 2009-15 ²⁾
fruit and vegetable supplies can be contaminated by enteric pathogens (mainly via pathogens in soil) via:
- production sites were previously used for waste disposal or animal rearing
- extreme weather events such as dust storms and flooding
- germinating seeds attracting enteric pathogens in soil
- sowing of pre-contaminated seeds
- contaminated irrigation water
bacterial pathogens can survive on leaves for several weeks to months via various colonization methods such as biofilms, cellulose synthase complex, internalizing into plant tissue through surface pores, etc.
risk of crop contamination by enteric pathogens increases as urban populations extend into the countryside
a US 2025 study suggested that 18% of UTI's are due to the same E.coli strain contaminating meat (esp. poultry) and that lower socioeconomic areas, women and older men were most at risk³⁾

organism	time to symptoms	food source	duration
food toxin mediated
Bacillus cereus	1-2hrs	rice	12-24hrs
Staphylococcus aureus	2-6hrs	meat, milk	6-24hrs - mainly vomiting
Clostridium botulinum	18-36hrs	canned food	weeks
ciguatera toxin	15min-24hrs	reef fish	neurologic symptoms as well as gastro
scombroid	10-30min	spoiled fish	anaphylactoid response due to ingestion of biogenic amines, especially histamine
blue-green algae (BGA) toxins in waterways		blue-green algae water

pathogenic
Salmonella	8-48hrs	poultry, eggs, salads, water	1-7 days, often blood diarrhoea
Vibrio parahaemolyticus	12-48hrs	crabs, shellfish	2-5 days
norovirus	12-48hrs	shellfish, salads, direct spread	1-3 days
Clostridium perfringens	8-22hrs	meat	12-48hrs mainly diarrhoea
enterohaemorrhagic E.coli	1-7 days	meat	7-21 days
enterotoxigenic E.coli	3-5 days	meat	acute watery diarrhoea
extraintestinal pathogenic E.coli strains (ExPEC)		meat, esp. poultry	UTIs⁴⁾
Campylobacter	1-10 days	poultry, milk, salads, water	diarrhoea may be bloody, minimal if any vomiting
Shewannella haliotis	3-49 days	raw fish, shellfish, most cases are in Asia in Summer	may cause hepatobiliary infections, bacteraemia, appendicitis with abscesses in elderly, those with hepatibiliary disease or the immunocompromised
typhoid	5-21 days	water, food handlers	weeks; initial green pea soup diarrhoea then ramping fevers
paratyphoid	more abrupt onset, and milder than typhoid	water, food handlers
shigella	1-3 days	water, food handlers (also STI)	dysentery type
cholera	1-5 days	water, food handlers	profuse watery diarrhoea
giardiasis	3-25 days	water, salads	1 to several weeks
cryptosporidium	1-12 days	water, salads	1-2wks if not immunocompromised; mainly diarrhoea
toxoplasmosis		creek water, rare red meats (heat > 66degC or freezing kills the parasite) - a study in 2020 showed that Australian lamb mince meat had over 40% chance of being infected⁵⁾, water soiled by cats	lifelong infection; may cause retinitis and floaters; dangerous to foetus or neonates or immunocompromised
other parasites		rare meats (esp. pork, fish, snails, etc); aquatic plants;	various, esp. GIT, tissue, liver, lung infections and rarely CNS - in 2023 a Canberra woman had a 8cm long live Ophidascaris robertsi python roundworm in her brain after using aquatic plants from nearby lake in cooking

¹⁾

https://www.news-medical.net/news/20240729/Health-authorities-warn-about-bird-flu-risks-in-raw-milk-and-undercooked-foods.aspx

²⁾

https://www.news-medical.net/news/20231106/Fresh-risks-in-ready-to-eat-produce-Study-reveals-how-common-pathogens-lurk-in-our-salads.aspx

³⁾ , ⁴⁾

2025: Zoonotic Escherichia coli and urinary tract infections in Southern California

⁵⁾

https://onlinelibrary.wiley.com/doi/epdf/10.1111/1753-6405.12955?src=getftr