Gastro Incubation Period: How Long Before Symptoms Hit (and How Long You're Contagious)

The big ones you'll encounter in Australia:

Norovirus. Incubation is 12 to 48 hours — usually closer to 24. This is the "24-hour bug" people talk about, though in reality most adults are ill longer than 24 hours. It spreads through contaminated food, water, surfaces, and person-to-person contact. One of the most contagious bugs going.

Rotavirus. Incubation is typically 1 to 3 days. More common in young children than adults, but adults aren't immune.

Salmonella. Incubation is 6 to 72 hours — commonly 12 to 36. Usually tied to contaminated food: undercooked poultry or eggs, unpasteurised dairy, certain raw produce.

Campylobacter. Incubation is 2 to 5 days. One of the most common bacterial causes in Australia. Often from raw or undercooked chicken.

E. coli (the illness-causing strains). Incubation is 3 to 4 days on average, sometimes up to 10. Associated with undercooked ground meat, unpasteurised dairy, and some fresh produce. Certain strains (like E. coli O157:H7) can cause severe illness and complications.

Shigella. Incubation is typically 1 to 3 days. Spread through contact with stool, contaminated food or water, and occasionally through sexual contact.

Giardia (parasite). Incubation is longer — 1 to 3 weeks. Often linked to drinking untreated water while camping, hiking, or travelling.

Food poisoning from preformed toxins (e.g., Staph aureus). Symptoms can hit within 1 to 6 hours of eating contaminated food. It's the bacteria's toxins, not the bacteria themselves, making you sick — so you may already be recovering by the time you think about what you ate.

For context on how these progress once symptoms start, see Gastro in Adults: The 5 Stages.

This is the question that matters for work, school, and keeping the rest of your household well.

Norovirus. You're typically contagious from the moment symptoms start, and most guidelines recommend staying away from work, school, and food handling for at least 48 hours after diarrhoea and vomiting have stopped. Some people shed virus for up to two weeks after symptoms resolve — less infectious, but not zero risk, particularly for high-risk contacts (elderly, immunocompromised, or young children).

Rotavirus. Contagious during illness and up to about 10 days afterwards. 48 hours after symptoms stop is the standard exclusion window.

Salmonella, Campylobacter, Shigella, E. coli. Contagious while shedding in stool — which can continue for days to weeks after symptoms stop. Guidelines generally recommend staying off work/school/food handling for at least 24 to 48 hours after symptoms resolve, longer if you work in high-risk settings (food handling, healthcare, childcare). Some organisms require a negative stool test before returning.

Giardia. Can be shed in stool for weeks, sometimes months. Treatment and thorough handwashing are important.

Staph food poisoning. The toxins aren't passed person-to-person, so you're not typically contagious — but the contaminated food source may be.

A common rule of thumb across most guidance: "48 hours clear" after vomiting or diarrhoea stops, particularly if you work in food, healthcare, or with young children. Individual public health advice may be stricter depending on the pathogen and your workplace.

Australian public health guidance is clear: people with gastro symptoms should stay home from work, school, childcare, and food handling until they've been symptom-free for at least 48 hours — often longer for workers in high-risk settings.

Workplaces. Most employers accept a medical certificate for gastro. If you need one, a telehealth GP can issue it without you needing to leave the house — see how to get an online medical certificate in Australia or Doctor's Note vs Medical Certificate in Australia.

Schools and daycares. Most have explicit 48-hour exclusion policies after vomiting and diarrhoea stop. Some require confirmation from a GP before a child returns.

Food handlers. State guidelines are stricter. Many jurisdictions require clearance from a medical practitioner, and some pathogens require a negative stool test before returning to work.

Healthcare workers. Generally required to be at least 48 hours symptom-free, sometimes with additional clearance. Check your employer's specific policy.