Influenza in Child
Alerts and Notices
SynopsisInfluenza (flu) is a universally common epidemic illness caused by several subtypes of type A or by type B influenza virus. (Type C influenza virus exists and produces a mild respiratory illness but is not believed to cause epidemics.) The most common subtypes of influenza A are H1N1 and H3N2. A subtype of avian influenza A that emerged in Asia (H5N1) produces infrequent but often fatal human illness. A swine-origin influenza A (H1N1) virus outbreak, beginning in March and April of 2009, reinforces that interspecies transmission of human and animal influenza A viruses and subsequent reassortment are possible and occur, resulting in new viruses that may spread to humans and even easily between humans.
Current flu season: Per the Centers for Disease Control and Prevention (CDC), in the week ending April 1, 2023, seasonal influenza activity remained low across the United States, and hospital admissions remained low. During week 13 of 2023, 59.1% of viruses reported by public health laboratories were influenza A and 40.9% were influenza B. Of the 16 influenza A viruses detected and subtyped during week 13, 37.5% were influenza A(H3N2) and 62.5% were influenza A(H1N1). Coinfection with influenza A or B viruses and SARS-CoV-2 can occur.
Influenza is highly contagious and is spread by aerosol droplets. The incubation period is 1-4 days, but it becomes contagious 1 day prior to the onset of symptoms. The mortality rate of influenza is low but tends to be higher in the elderly and the immunocompromised. Flu activity usually peaks in February.
Influenza presents with classic flu-like illness consisting of the sudden onset of fever, malaise, sore throat, nonproductive cough, myalgias, headache, and nasal congestion. Chills are common, as are nausea and vomiting in children. After 48 hours, cough may increase and produce sputum. There may be associated dyspnea and/or mild-to-moderate pleuritic chest pain. Upon physical examination, unilateral or bilateral inspiratory rales may be appreciated or diminished breath sounds. Pregnant individuals are at increased risk for severe illness from influenza.
Most viruses that affect the respiratory tract can cause a rash, flu included (see viral exanthem).
The most common pulmonary complication of influenza is secondary bacterial pneumonia. This diagnosis can be determined by patient history. This can occur up to 2 weeks after the initial symptoms and includes recurrence of fever, chills, pleuritic chest pain, and productive cough. Many bacteria may be the culprit, but the most common are pneumococci. Staphylococcus aureus has also been implicated in children; there has been an increase in the number of deaths in which both influenza and pneumonia or bacteremia due to S aureus were identified.
Primary viral pneumonia is the complication responsible for the most influenza-related deaths. Those with pre-existing cardiopulmonary disease or who are pregnant are at the greatest risk. The initial clinical presentation is the same, but dyspnea increases in severity. Productive cough may be blood tinged. Massive hemoptysis has been reported. When severe, there may be profound respiratory distress with tachypnea, tachycardia, and cyanosis. Rales and wheezes will spread throughout the chest from the lower lung.
The Spanish flu pandemic of 1918 was particularly virulent, killing over 20 million people worldwide. With present day biotechnology, it would be possible to produce an influenza virus weapon with traits of both the H5N1 and the 1918 influenza viruses. As a weapon, influenza could be released as an aerosol.
Note: In 2022 and 2023, pediatric invasive group A streptococcal (iGAS) infections and noninvasive group A streptococcal infection cases have been associated with respiratory infections due to influenza, among other viruses. Concurrent or preceding viral infections, including varicella (chickenpox), may increase risk for iGAS infection. Severe outcomes of iGAS infections include necrotizing fasciitis, streptococcal toxic shock syndrome, and death.
J10.1 – Influenza due to other identified influenza virus with other respiratory manifestations
6142004 – Influenza
Differential Diagnosis & PitfallsThe differential includes other viral respiratory diseases that present with a flu-like illness. The season and local occurrences of influenza should be considered.
- Avian influenza
- Parainfluenza viruses
- Respiratory syncytial virus
- Legionellosis (Legionnaires' disease)
- COVID-19 – Coinfection with influenza A or B viruses and SARS-CoV-2 can occur.
- Streptococcus pneumoniae pneumonia
- Mycoplasma pneumonia
Patient Information for Influenza in Child
OverviewInfluenza, or the flu, is a contagious illness caused by any one of the influenza viruses. It affects the nose, throat, and lungs, and usually includes symptoms of fever, headache, muscle aches, and weakness. The severity of symptoms can vary from person to person, and the flu can even cause death in individuals who have severe symptoms.
There are many different influenza viruses, and they usually spread in seasonal epidemics dominated by a particular strain or strains. Some strains are known to be more dangerous than others and can cause severe symptoms for people who are the most at risk. You may occasionally hear the names of different strains in the news, such as H1N1 or H5N1.
Who’s At RiskInfluenza is usually transmitted by coughs and sneezes. In addition, hand-to-hand contact, other personal contact, or even contact with objects handled by those with the flu is enough to transmit the virus. If others nearby have the flu, you may be at risk for an infection with an influenza virus.
Although all people are at risk for developing the flu when exposed to an influenza virus, some people are more likely to have severe symptoms. Those people include:
- Newborns and children up to 4 years old
- Pregnant individuals
- People over 65 years of age
- Children aged 6 months to 18 years on long-term aspirin therapy
- People who have chronic lung or heart disease
- People who have chronic metabolic disease (including diabetes), kidney dysfunction, certain blood problems, blood disorders (including sickle cell disease), or decreased immune function (including that caused by medications or by diseases, such as HIV / AIDS)
- Those with conditions that affect the function of the lungs
- Those with neurological conditions – disorders of the brain, spinal cord, and/or nerves including cerebral palsy, epilepsy, muscular dystrophy, or spinal cord injury
- Nursing home or chronic-care facility residents
Signs & SymptomsSymptoms of the flu usually begin suddenly. These symptoms include:
- High fever lasting 3 days or more
- Muscle and body aches
- Fatigue (feeling tired or exhausted) and weakness
- Sore throat, sneezing, and stuffy nose
- Diarrhea and vomiting – more common in children
Sometimes influenza weakens the immune system so much that it makes it easier for people to develop other diseases. These "complications" of influenza occur in people at high risk for developing severe symptoms (see Who's At Risk). The most common problem is pneumonia, which causes symptoms of long-lasting fever and shortness of breath. Other lung-related problems include worsening chronic bronchitis or asthma. Other complications like diarrhea in adults, kidney problems, and nervous system problems can also occur but are usually rare.
Self-Care GuidelinesProtecting yourself from getting the flu is an important part of self-care. This includes limiting contact with sick people and washing your hands often with soap and warm water or using an alcohol-based hand sanitizer.
In addition, getting a yearly flu vaccine is a good way to avoid contracting the flu or to at least keep the symptoms short and manageable. The United States Centers for Disease Control and Prevention recommend that everyone 6 months of age and older get an influenza vaccine every year. Vaccination is especially important for people at higher risk for complications (see Who's At Risk).
If you begin to show symptoms of the flu, the following steps can be taken to decrease the severity of symptoms:
- Stay at home and rest in bed for at least 24 hours after fever goes away.
- Lukewarm baths may help improve symptoms.
- Take regular temperature measurements and record the values.
- Remove blankets and heavy clothing, and dress in light clothing to allow heat to leave the body and reduce fever.
- Drink cool fluids frequently to prevent dehydration caused by fever.
- Some medications may help reduce fever.
- Children under age 19: acetaminophen or ibuprofen as directed to reduce fever and help with muscle aches. Note: NEVER give aspirin (acetylsalicylic acid) to anyone under the age of 19 with the flu, unless directed by your doctor.
- Adults: aspirin, acetaminophen, or ibuprofen as directed to reduce fever and help with muscle aches.
Cough, sore throat, sneezing, and stuffy nose:
- Soothe a sore throat by gargling with warm salt water or using cough drops or lozenges (for adults or older children).
- Medications should only be given to patients aged 5 years and older.
- Take over-the-counter medications to treat cough, sore throat, sneezing, and stuffy nose.
- "Expectorants" – loosen phlegm
- "Decongestants" – reduce stuffiness
- "Antihistamines" – dry up a runny nose
- Age-appropriate fever-reducing medications can help with a sore throat.
- Give liquids (if tolerated) with electrolytes (salt and sugar) to prevent and treat dehydration caused by vomiting and diarrhea. Wait for vomiting to subside for at least 1 hour to allow the stomach to rest before giving water in small amounts every 10 minutes.
When to Seek Medical CareSeek medical care if you have:
- Fever that does not come down
- High temperature (greater than 100.4°F [38°C] in infants, greater than 102.0°F [38.9°C] in older children, and greater than 104.0°F [40°C] in adults and children over the age of 5)
- Immune system disease or take medications or treatments affecting the immune system
- A lack of response to fever-reducing medications
- Severe muscle pain or stiff neck
- Coughing that produces blood
- Breathing changes such as breathing too quickly or difficulty breathing
- Chest pain or stomach pain
- Repeated vomiting that lasts more than an hour
- Severe, runny diarrhea
- Sudden dizziness or confusion
- Bluish skin color
- Cough that makes a harsh, barking noise
- Not drinking enough fluids
- Not waking up or interacting
- Being so irritable that they resist being held
- Fever with rash
- Signs of dehydration – dry eyes, dry mouth, fewer wet diapers, no tears when crying
TreatmentsSometimes, antiviral medications are used to treat and/or prevent influenza. These include:
Influenza in Child