A February 2025 fact sheet from the World Health Organization (WHO) classifies children under five as being at higher risk of severe influenza and says high-risk or severely ill patients should receive antiviral medicines as soon as possible. The guidance also says other respiratory viruses can produce influenza-like illness, so cough, fever, a runny nose, a sore throat or body aches cannot establish the cause on their own.

Most mild respiratory illnesses can be managed with rest, fluids and observation, but the child's overall condition matters more than any single symptom. Breathing effort, alertness, fluid intake and urination provide a faster safety check than trying to identify an infection from the color of nasal mucus.

Breathing, alertness and hydration signs come first

The US Centers for Disease Control and Prevention (CDC) lists fast or difficult breathing, ribs pulling inward, blue lips or face, chest pain, dehydration, reduced alertness and seizures among children's emergency warning signs for flu complications. Its dehydration examples include no urine for eight hours, a dry mouth and no tears when crying.

Immediate medical care is warranted when any of those signs appears. The same US guidance also includes any fever in an infant younger than 12 weeks, severe muscle pain that stops a child from walking, a chronic condition that worsens, or a fever or cough that improves and then returns or worsens.

The US list is not exhaustive. Another severe or rapidly worsening change calls for prompt assessment through the urgent or emergency service where the child is located, without waiting to see whether fever medicine changes the warning sign.

Symptoms do not settle cold versus influenza

Influenza often begins abruptly with fever, cough, headache, aches, fatigue, a sore throat or a runny nose, but not every child with flu has a fever. Other viruses can create a similar pattern, and a laboratory test may be needed when identifying the virus would affect treatment or infection-control decisions.

The US CDC says influenza antiviral treatment works best when started within two days of symptom onset, although some children can still benefit when treatment starts later. A clinician decides whether treatment is appropriate; antiviral availability, prescribing rules and regulatory status vary by country.

Young children and children with chronic conditions

WHO places children under five among the groups at higher risk of severe influenza. Its list also includes people with chronic heart, lung, kidney, metabolic, neurodevelopmental, liver or blood conditions and those with suppressed immune systems.

A child in one of these groups needs earlier clinical contact when influenza is suspected, even if the first symptoms appear mild. Existing asthma plans, specialist instructions and prescribed medicines take priority over general home-care guidance, and regular medicines should not be stopped or changed without the prescriber's direction.

Mild illness care centers on fluids, rest and observation

For mild influenza symptoms without warning signs, WHO advises staying home, resting, drinking enough fluids and seeking care if the illness worsens. During observation, the useful changes to track are breathing effort, interaction when awake, ability to drink and urination.

Covering coughs and sneezes with a tissue, disposing of the tissue and washing hands can reduce spread. Close contact with household members at higher risk of severe respiratory illness should be limited while the child is unwell.

The US Food and Drug Administration (FDA) lists saline nose drops or spray and a cool-mist humidifier among options for congestion in infants and children. These measures may ease symptoms but do not identify the infection or replace assessment when warning signs appear.

Check every active ingredient before giving medicine

The US FDA warns that many nonprescription cough and cold products contain several active ingredients, creating an overdose risk if too much is given, doses are repeated too often or two products contain the same drug. Medicine packaged for adults should not be given to a child.

In the United States, the FDA says cough and cold products containing a decongestant or antihistamine should not be given to children younger than two, and manufacturers label these products against use in children younger than four. Those are US recommendations and labels, not worldwide rules; formulations and age limits must be checked for the country and product involved, with a clinician or pharmacist when uncertain.

A fever reducer may ease discomfort, but it does not identify the cause of an illness or make an emergency warning sign safe to watch at home. The active ingredient should be checked across every prescription and nonprescription product so that a fever or pain medicine is not given twice, and the locally supplied label or clinician's instructions determine its use.

Antibiotics do not treat an ordinary viral cold

The US CDC says antibiotics do not work against viruses that cause colds, runny noses or influenza, even when nasal mucus is thick, yellow or green. Unneeded antibiotics can cause adverse reactions and contribute to antimicrobial-resistant infections.

An antibiotic prescribed for another person or left from an earlier illness does not answer that diagnostic question. If a clinician prescribes one for a confirmed or suspected bacterial infection, the prescription instructions govern its use.

School return depends on recovery and local rules

US CDC school guidance says policies can allow return after a child has been fever-free without fever-reducing medicine for at least 24 hours and respiratory symptoms have improved overall for at least 24 hours. It also says the child should be able to participate, manage an improving cough or congestion and avoid requiring a level of care that disrupts teaching.

The US agency directs schools to follow state and local health guidance alongside those criteria. Pathogen-specific rules, an outbreak or an individual child's medical plan can therefore change the return date.

UK public-health guidance allows an otherwise well child with a mild runny nose, sore throat or slight cough to attend an education setting, while a child who is unwell with a high temperature should stay home until the temperature has resolved and the child is well enough to attend. The difference from the US wording shows why attendance rules need a named jurisdiction.

APPI News could not find a single WHO return-to-school rule covering every childhood respiratory infection at the time of writing. The US and UK criteria above are examples from those jurisdictions, not a global attendance standard, and the child's school or local public-health authority may set a different rule.

Common questions

Can symptoms alone show whether a child has flu?
No. Influenza, the common cold and other respiratory infections share symptoms, and testing or clinical assessment may be needed when the distinction would change care.

Is influenza treatment no longer useful after two days?
Not necessarily. US CDC guidance says antivirals work best when started within two days, but later treatment can still benefit some children, particularly those at higher risk or with severe illness; a clinician makes that decision.

Can a fever medicine and a cold medicine be used together?
Only after every active ingredient has been checked against the child's prescription and nonprescription medicines. Combination cold products may already contain a fever or pain medicine, and pediatric age limits and instructions differ by country and product.

Does a lingering cough always prevent school attendance?
No single rule applies worldwide. Return depends on the cause, whether symptoms and fever meet local criteria, whether the child can participate and manage the cough, and whether the school or local health authority has additional requirements.