What happens on each day of an adenovirus infection and when to see a doctor. Based on the Russian Ministry of Health clinical guidelines and CDC data.
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The diagram is simplified: timelines come from the Russian Ministry of Health clinical guidelines on acute respiratory viral infections in children and CDC data; in any one person the illness may go differently. The guidelines count virus shedding from the day of infection, not from symptom onset [1][2].
For children older than 3 months, bringing a fever down with medicine is justified above 38.5 °C (101.3 °F) [1]. Only acetaminophen (paracetamol) or ibuprofen; children are not given aspirin [1].
Virus shedding peaks on day 3 after infection, not day 3 of the illness: part of that time falls in the incubation period [1]. A sick child stays home [1].
Day 4
Fever for more than 3 days
In 82% of patients with an acute respiratory viral infection, the fever goes down on day 2–3 [1].
If a temperature above 38.4–38.5 °C (101.1–101.3 °F) lasts more than 3 days, the child needs to see a doctor again [1].
Days 5–7
Adenovirus fever lasts longer
With adenovirus infection and flu, a temperature above 38 °C (100.4 °F) can last up to 5–7 days [1].
A high fever lasting more than 4–5 days that does not come down with fever reducers is a reason to admit a child to the hospital [1].
Virus shedding drops quickly by day 5 after infection (this is not necessarily day 5 of the illness) [1].
A runny nose and cough after a cold can last another 1–2 weeks [1].
Low-level virus shedding can continue for up to 2 weeks [1].
If a stuffy nose or cough does not go away within 10–14 days, especially with a new rise in temperature, see a doctor [1].
Days 15–21
More than two weeks
After recovery the virus is sometimes shed for a long time, especially in people with weakened immune systems — usually without symptoms [2].
A lingering cough or a new turn for the worse is a reason to see a doctor again [1].
When not to wait
Warning signs that mean you should call your local emergency number (911 in the US, 999 in the UK, 112 in the EU) do not depend on the day of illness. The list is in the article adenovirus in children.
CDC (US Centers for Disease Control and Prevention). About Adenovirus. Updated December 16, 2025. Accessed October 7, 2026.
This article was prepared by our editorial team from official sources and does not replace a doctor’s advice. Found an error? Write to us.
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