How Long Is Flu Contagious?
Understanding this window helps set realistic expectations for both sick leave duration and return-to-work timing.
Before symptoms appear
A person can typically be contagious about 1 day before symptoms start — one reason flu spreads before anyone realises they’re unwell.
During symptomatic illness
Contagiousness is generally highest in the first 3–4 days of illness.
After symptoms ease
Adults may remain contagious for up to 5–7 days total; children and immunocompromised individuals can shed virus for longer.
These are general ranges from public health guidance and vary by individual and strain. Because the contagious window starts before symptoms are obvious, workplace prevention — hand hygiene, surface disinfection, good ventilation — matters as much as reacting to visible illness. See staying healthy this flu season for the practical measures.
This page provides general information and is not medical advice. If you or a household member is unwell, follow current guidance from your healthcare provider.
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