Flu in Children: Symptoms, Antiviral Medicine, and Emergency Warning Signs

Flu in children usually starts suddenly with fever, cough, sore throat, body aches and tiredness, and many children recover at home with rest and fluids. It becomes urgent when a child struggles to breathe, is hard to wake, has a seizure, or cannot keep fluids down. This article explains how flu looks in children, how it differs from a cold, what antiviral medicine can and cannot do, and which warning signs need 911 or same-day care.

What flu in children looks like

Influenza is a contagious respiratory illness caused by influenza viruses. MedlinePlus (NIH) describes common flu symptoms as fever, chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headache and tiredness. Children can have all of these, and they often come on over a short stretch rather than building slowly over several days.

Children also show flu in ways adults may not. A toddler may not be able to say "my body hurts" and may simply be clingy, cranky, or unwilling to play. Some children have vomiting or diarrhea along with the respiratory symptoms, and young infants may be sleepy, feed poorly, or have a fever with few other signs.

Flu, cold or stomach bug: how to tell them apart

Several illnesses overlap, and a clinician usually combines your child's history, an examination and sometimes a test before naming the cause.

• Flu: often sudden fever, aches, marked tiredness, and a dry cough. Children may seem much sicker than with a cold.
• Common cold: usually milder, with a runny or stuffy nose and sneezing as the main complaints. MedlinePlus notes that colds are caused by many different viruses.
• Stomach bug: mainly vomiting and diarrhea. MedlinePlus describes gastroenteritis as inflammation of the stomach and intestines, often from a virus. Flu can cause these symptoms in some children, so the picture is not always clear.

Other infections, including COVID-19 and RSV, can look similar. A flu test, usually a nose or throat swab, can help your child's clinician decide on treatment. A clinician can also treat based on symptoms during flu season, and the CDC's antiviral summary for clinicians indicates that treatment for a high-risk or very sick child should not wait for a test result.

Antiviral medicine for children with the flu

Antiviral medicines work against the influenza virus itself. They do not cure the illness instantly. The CDC's flu treatment page explains that antivirals can make illness milder and shorten it when started early, and may reduce the chance of some complications. Outcomes vary from child to child. An antiviral does not replace the yearly flu vaccine.

Prescription antivirals used for influenza include:

• Oseltamivir (Tamiflu): taken by mouth, usually as a liquid for younger children. It is the one most often prescribed for children, and clinicians can prescribe it for infants as well, based on age, weight and the product label.
• Baloxavir (Xofluza): a different type of antiviral, approved for certain ages and situations.
• Zanamivir (Relenza): an inhaled powder. Its labeling includes a caution about breathing problems in people with airway disease such as asthma, so it may not suit a child with asthma.
• Peramivir (Rapivab): given through a vein, generally used in a clinic or hospital.

Antivirals generally work best when started early in the illness, so contact your child's clinician promptly if flu is suspected, especially in a higher-risk child (see below). Do not assume it is too late to ask. The CDC's antiviral summary for clinicians notes that clinicians may still consider treatment later in the illness for a child who is very sick, hospitalized, or at higher risk of complications.

Who the prescriber may want to treat

Not every child with flu needs an antiviral. Healthy older children with mild illness often recover with home care. The CDC recommends antivirals for children who are hospitalized, severely ill or at higher risk of complications, and says treatment may be considered for other children, ideally started early in the illness. Tell your clinician if your child has asthma, diabetes, a neurologic or neuromuscular condition, a weakened immune system, or another long-term illness. Asthma in children is a common example, because flu can make breathing harder in a child whose airways are already sensitive.

What to know about the label

Antivirals are prescription medicines, and the dose depends on your child's age and weight and on the product. Give the medicine exactly as the prescriber and pharmacist direct, rather than calculating a dose yourself. Common side effects of oseltamivir include nausea and vomiting, and taking it with food may help. If your child vomits soon after a dose, ask the prescriber or pharmacist what to do.

The oseltamivir labeling also describes reports of unusual behavior, confusion or other neuropsychiatric events in people with flu, mostly children, and it is not clear whether the medicine or the illness itself causes them. Watch your child's behavior during the illness. Call 911 if your child is unresponsive, cannot be roused, or is acting in a way that puts them in danger. For severe confusion or hallucinations that are not immediately dangerous, seek emergency evaluation right away. For milder changes that seem off, tell the prescriber right away. Swelling of the face or throat, trouble breathing, or a blistering rash after a dose can signal a severe allergic or skin reaction and needs 911. For hives alone, call the prescriber or pharmacist right away. Do not change the timing or amount of a prescription, or stop it early, without asking the prescriber.

Antibiotics do not treat influenza because it is caused by a virus. A clinician may prescribe one if your child develops a bacterial complication such as an ear infection, sinus infection or pneumonia.

Comfort care at home

Most children with flu are cared for at home. The goals are comfort, fluids and watching for worsening.

• Fluids: offer small, frequent sips of water, oral rehydration solution, or breast milk or formula for babies. Appetite often drops, and that is usually fine if your child is drinking.
• Rest: let your child sleep and play quietly as energy allows.
• Nose and throat care: saline drops with gentle suction can help babies, and a cool-mist humidifier or warm drinks may ease cough and throat discomfort for older children.
• Fever and aches: acetaminophen (Tylenol) may help your child feel better, and ibuprofen is another option for children old enough for it on the label, since ibuprofen products set a minimum age. Ask the pediatrician before giving any fever reducer to a baby under 3 months. Ibuprofen is generally avoided in babies under 6 months and when a child is dehydrated or vomiting. Read the product label for age limits and directions, and ask your pharmacist or pediatrician about the right amount. Our article on children's Tylenol covers this topic.

Why aspirin is not a good choice

Do not give aspirin or products containing salicylates to a child or teenager with flu-like illness unless a doctor specifically directs it. Aspirin has been linked to Reye syndrome, a rare but serious condition that can cause swelling in the liver and brain after a viral illness. Some stomach remedies, such as bismuth subsalicylate products, contain a related ingredient, so check labels on cold and stomach medicines and ask your pharmacist if you are unsure.

Dehydration: the common problem to watch for

Fever, fast breathing, poor appetite, vomiting and diarrhea can all cause a child to lose more fluid than they take in. Signs of dehydration can include fewer wet diapers or less urine than usual, a dry mouth, crying with few or no tears, sunken eyes, unusual sleepiness and dizziness on standing. A child who cannot keep fluids down or is passing little urine needs same-day evaluation. A child who is also limp or very hard to wake needs emergency care. Our guide on how to tell if your child is dehydrated goes through these signs step by step.

Warning signs of serious flu in a child

Most children improve over several days to a week, though cough and tiredness can linger. Flu can occasionally lead to pneumonia, worsening asthma, dehydration, ear and sinus infections, brain inflammation (encephalopathy), muscle inflammation, or a severe inflammatory response to infection. Serious complications are much less common than ordinary flu, but they can progress quickly, which is why the signs below matter.

Breathing, chest pain and color

Struggling to breathe is the main emergency in flu. Look for fast breathing, skin pulling in between or under the ribs or at the neck with each breath, nostrils flaring, grunting, or a child who cannot speak or cry in full sentences or phrases because of breathlessness. Blue or gray lips, face or nails suggest the body is not getting enough oxygen. Call 911 for these. Chest pain or pressure with trouble breathing, fainting or a very ill appearance needs emergency care, because it can go along with pneumonia, inflammation around the lungs, or inflammation of the heart muscle.

Alertness, muscle pain, seizures and rash

A child who is very hard to wake, limp, or unresponsive needs emergency care, and so does a child with severe confusion. So does a child who is awake but not alert or not interacting with you the way they normally would. Severe muscle pain with refusal to walk or bear weight needs urgent same-day evaluation, and sooner if urine is dark or weakness is present, because flu can sometimes inflame muscle tissue. A seizure during flu can happen with a high fever or from brain involvement. Call 911 if a seizure is prolonged, repeats, leaves your child with trouble breathing, or your child does not return to normal afterward. Any first seizure needs urgent medical evaluation. A rash that looks like purple or bruise-like spots in a child who looks very ill can be a sign of a serious bloodstream infection and needs emergency care.

Young infants

A rectal temperature of 100.4°F (38°C) or higher in a baby under 3 months needs same-day emergency evaluation, usually at an emergency department, even if the baby has no other symptoms, because infants can become seriously ill quickly. Call 911 if the baby is limp, blue or gray, struggling to breathe, or very hard to wake. A baby who is feeding poorly and has few or no wet diapers needs urgent evaluation, usually at an emergency department, and 911 if the baby is also limp, very sleepy or struggling to breathe.

Getting better, then worse

Some children improve for a short time and then develop a returning fever with a worse cough, ear pain, or new difficulty breathing. This pattern can suggest a secondary bacterial infection such as pneumonia. A returning fever, worse cough or ear pain calls for same-day evaluation, while breathing trouble or chest pain moves it into the emergency category above.

Higher-risk children

Any child can become seriously ill with flu, including healthy ones. The CDC lists children under 5, and especially under 2, among those at higher risk of serious flu illness, and young children can dehydrate quickly. Children with asthma, diabetes, heart or lung disease, neurologic conditions, or a weakened immune system also face higher risk. Contact your child's clinician early in the illness if your child falls into one of these groups. If your child has diabetes, illness can affect blood sugar, so ask your diabetes care team for a sick-day plan.

Preventing flu and protecting others

Yearly vaccination is the main way to reduce the chance of flu and of severe illness. MedlinePlus (NIH) describes the flu shot and who should receive it. Ask your pediatrician which vaccine type and schedule fit your child's age, since some children under 9 need two doses in their first season of vaccination. Babies under 6 months are too young to be vaccinated, so vaccination of household members and caregivers helps protect them.

Handwashing, covering coughs, and keeping a sick child home help limit spread. Check your school's policy on returning after a fever.

When to Seek Medical Care