Flu in Children (Childhood Influenza)

High fever, vomiting, muscle aches, sore throat, headache, and cough are symptoms and signs of the flu.

Influenza is an acute viral infection caused by any of three types of influenza viruses (A, B, or C). Type A strains are associated with the most severe disease. Type C is associated with very mild symptoms and is not included in flu vaccines. Many people confuse influenza or flu with the common cold. They are different. The common cold can be caused be a variety of viruses that infect the upper respiratory tract (nose, mouth, and throat) and tends to be self-limited, requiring only rest and hydration. Flu is caused by a specific member of the influenza virus family and is often more severe and more dangerous than a cold, particularly for children under 5 years of age and the elderly. The Center for Disease Control and Prevention (CDC) reported that 190 children died due to influenza during the 2017-2018 flu season. The viruses that cause influenza are different from those that cause gastroenteritis (often referred to as "stomach flu") which has symptoms such as nausea, vomiting, and diarrhea.

During the 2018-2019 influenza season, the CDC compiled the following statistics.

1. 35.5 million experienced a characteristic flu illness.
2. 16.5 million visited their doctor or were evaluated in emergency rooms or other facilities for influenza symptoms.
3. 490,000 were hospitalized (usually children less than 2 years of age or older individuals).
4. 34,200 died from influenza directly or complications (136 children died).

Influenza usually spreads locally from person to person during flu season. This is referred to as epidemic flu. Because there is very little preexisting immunity, occasionally a very different strain emerges and spreads rapidly worldwide. This is known as pandemic flu. For example, in 2009, a new type A strain emerged called H1N1. Because there was little immunity in the human population to the H1N1 strain, it had the ability to spread easily from person to person worldwide and sicken even more people than a usual seasonal strain. In July 2009, a worldwide pandemic of H1N1 was declared by the World Health Organization (WHO). This pandemic ended in August 2010.

• Influenza is an acute infection of the airway tract in the nose and throat that can sometimes spread into the lungs. Flu in adults is a frequent cause of acute respiratory illness. Flu, however, affects people of all ages. Children are among the groups most at risk for developing flu and its complications and are more likely to spread the infection to others.

Flu season (a sharp increase in reported cases) usually begins in late fall and early winter, and cases usually spread widely. The peak season for the flu in the northern hemisphere is from November through March, although cases can be seen all year long.

The flu is caused by one of three types of influenza viruses. Types A and B are responsible for the yearly flu epidemics, and type C causes a milder, sporadic illness. Type A is further divided into different subtypes based on the chemical structure of the virus.

Children play a major role in the spread of influenza in their communities because high numbers are exposed to the influenza viruses at schools and day care centers. Overall, as many as 30% of children may become infected during a regular flu season, and in some day care settings, as many as 50% of children can get the flu. Healthy children may limit the spread of influenza virus by staying home when ill, covering their mouth and nose when coughing or sneezing, and washing their hands with either soap and water or with alcohol-based products.

Influenza is highly contagious. The virus is spread when someone either inhales infected droplets in the air (coughed up or sneezed by an infected person) or when someone comes in direct contact with an infected person's secretions (for example, kissing, sharing of handkerchiefs and other items, and through use of objects such as spoons and forks) and then inadvertently touches their nose or mouth, thus transferring the virus particles. Droplets carrying flu virus from a sneeze or cough typically can travel up to 6 feet and may spread the infection if they are inhaled. The influenza virus can live on objects (for example, glasses or eating utensils) for 3 -5 days depending on the strain.

Children with influenza may be able to infect others beginning one day before they develop any symptoms and may remain contagious for up to seven more days or sometimes even longer. Some children may be able to transmit the flu to others even though they, themselves, do not feel very sick. Because transmission can occur before a patient has any symptoms, the flu spreads rapidly. A usual school/work requirement is to be fever free for 24 hours before returning to the classroom or workplace.

The incubation period for flu in children is usually two to four days from exposure until symptoms begin.

Symptoms usually begin two to four days after exposure to the virus and typically develop quickly.

• Classic symptoms include high-grade fever up to 104 F (40 C), chills, muscle aches, headaches, sore throat, dry cough, and malaise (just plain feeling sick). These symptoms usually last for three to four days, but cough and tiredness may linger for one to two weeks after the fever has gone away. Other family members or close contacts often have a similar illness.
• In younger children, the pattern of influenza may be a typical influenza-like illness or look like other respiratory tract infections such as croup, bronchitis, or pneumonia. Abdominal pain, vomiting, and diarrhea are frequently observed in children. Vomiting tends to be more significant than diarrhea. Fever is usually high, and irritability may be prominent.
• In infants, the flu often goes unrecognized because the signs and symptoms are not specific and may suggest a bacterial infection. Influenza in infants younger than 6 months of age is less common, but symptoms include lethargy, poor feeding, and poor circulation. Parents of infants need to be vigilant regarding their child's fluid intake, any evidence of increasing the work of breathing (for example, unusual respiratory rate and depth), and their overall social interaction with their parents. Observing how often the diaper is wet can be helpful as a first sign of dehydration.
• Complications from the flu include pneumonia, ear infections, or sinus infections and flu may aggravate chronic health conditions such as asthma, heart failure, or diabetes.

The most difficult question for parents and caregivers is when to call the doctor with concerns about flu symptoms. Many people fear the child may have pneumonia. Here are some guidelines about when to call the doctor:

For children under 5 years of age and especially if under 2 years of age, and for children of any age who have chronic illnesses such as asthma, speak to the doctor early to decide if the child needs to be examined.

For those 5 years of age and older, call if you are worried or if

• fever continues after three days,
• nasal discharge lasts more than 10 days,
• nasal discharge becomes thick and yellow or green for more than four to five days, or
• discharge is coming from the eyes.

When to Go to the Hospital

• The child has difficulty breathing or is breathing rapidly and does not improve even after nasal suctioning and cleaning.
• Bluish skin color: If the child is struggling to breathe and has a bluish skin color, dial 911!
• The child appears sicker than any previous episode of illness. The child may not be responding normally. For example, the child does not cry when expected, does not make good eye contact with a parent, or the child is listless or lethargic.
• The child is not drinking fluids well or is showing signs of dehydration. Common signs of dehydration include absence of tears with crying, decrease in amount of urine (dry diapers), dry mucous membranes (lips, tongue, eyes), and dough-like skin that fails to snap back flat when pinched.
• Severe or persistent vomiting
• If an infant is unable to eat
• A fever that does not get better with appropriate dosing of acetaminophen (Tylenol) or ibuprofen (Advil). Either of these products should lower a child's temperature 1.0-1.5 degrees.
• Fever with a rash
• A seizure occurs.

Any of these symptoms indicate that a medical evaluation is appropriate.

Special Groups

Certain children are at higher risk of serious flu complications and may need medical attention earlier than usual.

• Children 6 months of age or younger are too young to be vaccinated. It is best that all household members and those around them are vaccinated in order to protect them via herd immunity.
• Young children aged 6 months to 5 years, even if otherwise healthy, are more likely to be hospitalized from the flu.
• American Indian and Alaskan Native children are more likely to be hospitalized with flu.
• Children with chronic health problems or medical conditions, including
  • pulmonary problems such as asthma and cystic fibrosis;
  • neurologic conditions like cerebral palsy, epilepsy, intellectual disability, developmental delay, muscular dystrophy, or spinal cord injury;
  • heart disease;
  • diabetes or other endocrine problems;
  • liver or kidney disease;
  • weakened immune system, such as HIV infection, cancer, or use of steroid medications;
  • children on long-term aspirin therapy.

If the child's illness is occurring during flu season, the doctor may judge the child to have flu simply from observing classic symptoms such as substantial fever (over 101 degrees), listlessness, and breathing problems in the upper respiratory tract and generalized muscle soreness.

• The doctor may take swabs of mucus from the nose or throat and send them for laboratory analysis. Several rapid diagnostic kits are now available with a fairly high degree of accuracy. The results may be available while still in the office. Sometimes flu will be missed with the rapid tests.
• Sometimes a chest X-ray film may be taken to make sure the child does not have pneumonia.

Flu symptoms may last more than a week. Caregivers can relieve and soothe children's aches and pains with basic home care.

• Rest in bed as needed.
• Allow the child to drink lots of fluids of the child's choice.
• Treat fever with acetaminophen (Children's Tylenol) or ibuprofen (Children's Advil, Children's Motrin) taken according to package instructions or consult the child's doctor. Ibuprofen should not be administered to children below 6 months of age. Do not give aspirin because it poses a risk of causing Reye syndrome. Reye syndrome is a potentially fatal illness that commonly affects the brain and liver.
• Use a humidifier in the child's room to make dry air easier to breathe.
• Children may need more careful attention for these symptoms.
  • Runny nose: Younger infants usually breathe through their nose and tend not to breathe through the mouth. Even older children have difficulty breathing through the mouth and sucking on something at the same time. Therefore, it is very important that the child's nose should be clean before feeding and before putting the child to sleep.
  • Suctioning is the method to clean the nose. For younger infants, use a rubber suction bulb to remove the secretions gently. Older children can blow their noses, but forceful blowing can push the secretions into the ear tubes or sinuses. Encourage the use of tissues and gentle nose blowing.
  • Dry or stuffy nose: It is important to remember that most stuffy noses are blocked by dry mucus. Blowing or sniffling alone cannot remove dry mucus. Use of saline nose drops is helpful in loosening the mucus. These nose drops are available at most drugstores. One minute after using the nose drops, use a soft rubber suction bulb to gently suck out the loosened mucus.

• Although it is best to eat soothing and nutritious foods, there is no need to force children with the flu to eat.
• Foods rich in protein, such as meats, eggs, dairy, and beans, may help to regain strength. Foods that are easy to eat, such as soups and ice pops (soothing for sore throats), are also good.
• A variety of fruits with vitamin C is recommended.

Most children with the flu will have relatively mild illness and do not need antiviral medications. However, for those with more severe illness or who have other chronic illnesses and children less than 2 years of age are at greater risk of developing complications, antiviral medicines may help.

Five influenza antiviral drugs are currently licensed in the United States and are available from a doctor by prescription. If given within the first 48 hours from onset of symptoms, antiviral agents decrease the severity and duration of symptoms, but their ability to prevent complications of influenza A has not been established. While these medications lessen the duration and intensity of symptoms, they do not cure the patient. It is also important to know that these medications do not affect the duration of contagiousness. The primary drawback of these types of medications is that resistant viruses can make them ineffective. As new medications are being developed all the time, make sure to discuss potential use of antivirals with your health care provider.

• Neuraminidase inhibitors (NAI) are FDA approved for uncomplicated influenza when the symptoms have been present for fewer than 48 hours. The main advantages of the NAI are their activity against both influenza A and B and activity against the current circulating strains. Zanamivir (Relenza) is approved for treatment in children older than 7 years of age, but it is not approved for prevention of developing influenza if exposed to the virus. The drug is available as topical powder administered by a breath-activated inhalation device. Oseltamivir (Tamiflu) is licensed for children older than 2 weeks of age and has been recommended by the CDC for children over 2 weeks of age when appropriate. It is available as a tablet and suspension and is usually taken for 5 days. In certain circumstances, Tamiflu may be administered as a preventative medication.
  • Peramivir (Rapivab) is approved for patients age 18 and older.
• M2 inhibitors include the drugs amantadine (Symmetrel and Symadine) and rimantadine (Flumadine). Both have been used in the prevention and treatment of influenza type A. However, the yearly changes in the circulating strains of influenza have made these drugs less effective. These antiviral agents are not effective against influenza B and are not approved for use in children younger than 1 year of age. Rimantadine has not been approved for treatment of children younger than 13 years of age. Amantadine and rimantadine have not been recommended by the Centers for Disease Control and Prevention (CDC) since the 2009-2010 influenza season. Laboratory testing by the CDC on the predominant strain of influenza (H1N1) currently circulating in the United States shows that it is resistant to amantadine and rimantadine and therefore should not be used.
• Currently, no antiviral agents exist for use against influenza C infections.
• The broad-spectrum antiviral agent ribavirin (Rebetol, Virazole Aerosol), given in aerosol form like nebulization, may be of benefit and is being studied. At the moment, its use is controversial and it is not recommended or FDA-approved for treatment or prevention of influenza in children.

Variant H3N2 Influenza

Since July 2012, there have been sporadic outbreaks of variant H3N2 flu (H3N2v). This is a different type of influenza A. These cases appear to be mainly spread from pigs to humans and have been seen where close contact between humans and pigs occurred, such as livestock exhibitions and fairs. Like seasonal flu, however, serious illness, resulting in hospitalization and death is possible from H3N2v. People at high risk of serious complications from H3N2v include children younger than 5 years of age, people with certain chronic conditions like asthma, diabetes, heart disease, weakened immune systems, pregnant women, and people 65 years and older. These people were urged by the CDC to avoid pigs and pig arenas at fairs this season.

Swine flu is a respiratory disease of pigs that is also an influenza virus type A family member. Sometimes these viruses also infect humans and are called variant viruses.

Avian flu (bird flu) is a disease caused by a specific influenza type A virus. This is mainly found in wild birds but can infect domestic poultry, as well. Rarely it can be transmitted to humans and can cause human disease. Three types of avian influenza that are known to cause disease in birds and humans are H5, H7, and H9. Contact with infected birds is a risk factor for human infection. One concern is that an avian influenza virus may mutate to allow easier spread from person to person and thus cause an epidemic or pandemic.

Since 2013, reports from China have focused on a new bird flu, H7N9, which is associated with contact with infected poultry. At the time of this article, there have been over 1,550 cases of confirmed human infection, but none have been associated with ongoing human-to-human transmission.

• Hand washing with soap and water or an alcohol hand gel is an important way to prevent picking up a flu virus. Avoid touching the mouth, nose, or eyes prior to hand washing.
• Avoid close contact with people who are ill. Droplets from a cough or sneeze can spread infection and are estimated to be able to travel about 6 feet and may live for several days on objects.

Prevention With Antiviral Medication

Two of the antiviral medications for flu are approved for use in children. Oseltamivir (Tamiflu) is recommended for the prevention of influenza in children 1 year of age and older. Zanamivir (Relenza) is recommended for prevention of influenza in children 5 years of age and older. If a child is exposed to influenza and is at higher than average risk of complications (see list above under Special Groups), a doctor may recommend taking one of these medicines before symptoms begin to try to prevent or decrease the severity of the flu.

• Vaccination is the mainstay of flu prevention. Influenza vaccine is given every year and is designed to best match the strain of flu that is predicted to be circulating during that flu season.
• The CDC recommends that everyone 6 months of age and older receive a yearly flu vaccine.
• Flu vaccines for children are available as injectable killed virus or a weakened virus stain given as a nasal spray. The vaccine either comes as trivalent (contains three strains) or quadrivalent (contains four strains). The CDC recommends the quadrivalent preparation.
• The killed, injectable vaccine is recommended for any child over 6 months of age.
• A nasal spray (FluMist) using a weakened strain of influenza virus is an option for those between 2-49 years of age. For those with selected conditions (for example, asthma, immune suppression, etc.) the injectable formulation is recommended. Children aged 6 months to 8 years who are being vaccinated for the first time need two doses a minimum of 1 month apart.
• Children aged 6 months to 8 years who are being vaccinated for the first time may need two doses about one month apart.

• The ability of the influenza vaccine to prevent the flu varies from season to season depending on how well the strains contained in the vaccine match the strains that are circulating in the population. An individual's health may also play a role. Each year the vaccine developers try their best to match the vaccine strains with the strains that are predicted to be circulating when flu season begins, but since the flu can change or mutate rapidly, the match is not always perfect.
• Many studies have shown that even if the flu shot is not a perfect match and does not completely prevent illness, those who have received the vaccine may have a milder and shorter illness.
• A study of flu vaccine in children showed that it reduced the risk of flu-related admission to intensive care units by 74%. Of the 136 children who died during the 2018-2019 influenza season, 74% were not immunized and approximately one-half had underlying at-risk medical conditions.
• Immunization of pregnant women was 92% effective in preventing hospitalization of their infants with flu.

The available influenza vaccine is prepared from killed influenza virus. As such it cannot give you the disease. Side effects generally are less intense and shorter in duration than the actual disease. There are several potential minor side effects that may follow vaccination against influenza and mimic symptoms of the illness. There are also very rare serious side effects that may occur.

Minor side effects include

• soreness, redness, swelling at the injection site;
• cough;
• sore throat;
• fever;
• muscle aches;
• headache; and
• fatigue.

Serious side effects include the following:

• With influenza vaccination comes a small increased risk of developing Guillain-Barré syndrome (GBS). GBS is a neurologic disease affecting muscle function. It is estimated that one to two cases of GBS result from 1,000,000 vaccinated individuals. It should be pointed out that the risk of severe consequences of the disease influenza exceeds the risk of developing GBS.
• Young children who receive flu vaccine, pneumococcal vaccine (PCV-13), and/or DTaP vaccine at the same time have a slight risk of having a seizure associated with a fever. Such febrile seizures occur in 3% of all children (often between 18 months to 3 years of age) during the course of an illness. Such seizures are not associated with neurological handicaps. You should inform your child's pediatrician if your child has ever had a seizure.

In most children, the fever and most other symptoms usually are gone in five days or less. Sometimes the cough and weak feeling may go on for one to two weeks. If complications such as pneumonia develop, then illness may last two weeks or more.

It often takes a few weeks to return to normal activity after the flu. The cough may last for weeks. Effective antiviral drugs have been shown to shorten the duration of illness by one to two days when therapy is started within 48 hours of symptom onset and are recommended for those at higher than average risk of complications (see list above under Special Groups).

Immunization against influenza will not provide immunity against other viral infections such as COVID-19 virus. However, influenza and COVID-19 infections share many of the same symptoms (fever, respiratory illness, muscle pain, headache, and fatigue). Immunization against influenza virus will lessen the likelihood of severe influenza illness and thus provide necessary life support items (ICU beds, ventilators, etc.) for COVID-19 patients or those with other illnesses (for example, heart attack, trauma, etc.).

Since the COVID-19 virus has never been in existence during the flu season, we have no historical perspective to answer this question. However, planning for such an option will help avoid a lack of necessary items to deal with patients who may have both illnesses at the same time.

Since the final version of a COVID-19 virus vaccine has not completed the FDA approval process, it is impossible to answer this question. Time will tell.

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National Institute of Allergy and Infectious Diseases
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American Lung Association
The American Lung Association
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New York, NY 10006
800-LUNGUSA

Children, the Flu, and the Flu Vaccine, Centers for Disease Control and Prevention

Flu.gov

Flu, MedlinePlus

Influenza (Flu), Centers for Disease Control and Prevention