Influenza (Children)

Influenza, commonly known as the flu, is a highly contagious viral infection usually affecting the respiratory system (nose, throat and lungs). The condition can sometimes affect several parts of the body, leading to severe illness, particularly in young children and the elderly. 

There are three types of influenza virus: A, B and much less commonly C. Influenza A viruses are further classified by 2 surface proteins (hemagglutinin and neuraminidase), as in H5N1 (avian flu, 1997) or H1N1 (swine flu, 2009). 

Influenza occurs year-round in Singapore, with two peak seasons, aligning with winter in the Northern (December to February) and Southern (May to July) Hemispheres. Influenza viruses are capable of rapid mutation and seasonal strain variation. Occasionally, influenza pandemics, such as the avian flu (H5N1) in 1997 and swine flu (H1N1) in 2009, caused widespread severe illness globally.  

Influenza virus spreads through tiny droplets when infected individuals cough, sneeze or talk. It can also spread through contact with contaminated surfaces such as doorknobs and phones. Incubation period typically ranges from 1 to 4 days, and the patient can be contagious even 2 days before symptom onset. Viral shedding can also continue beyond symptom resolution especially in young children and immunocompromised individuals.

Influenza symptoms range from mild to severe, including: 

• High fever lasting 3 to 7 days
• Runny nose
• Sore throat
• Headaches
• Cough
• Fatigue
• Body aches
• Diarrhoea and vomiting

These symptoms, similar to other respiratory virus infections, are usually self-limiting and often do not require any specific medical treatment.  

Risk factors for severe illness or complications include: 

• Young age (younger than 5 and especially younger than 2 years old) 
• Underlying lung conditions such as asthma, chronic lung disease, cystic fibrosis or bronchiectasis 
  
• Underlying heart or neurological conditions 
  
• Chronic kidney or liver disease 
  
• Diabetes mellitus or obesity 
  
• Weakened immunity such as in patients receiving medications that suppress the immune system 
  
• Pregnancy 
  

Such individuals will be at higher risk for complications such as pneumonia, brain or heart inflammation, exacerbation of chronic health issues and severe systemic effects, potentially leading to serious illness or death.  

Influenza can also be associated with secondary bacterial infections, commonly involving the middle ear, lungs or skin. Secondary bacterial infections will usually manifest as recurrence or worsening of fever or symptoms after the initial 1 to 2 weeks of influenza symptoms. 

Influenza is usually suspected based on symptoms and signs. The diagnosis may then be confirmed on swab testing using either rapid antigen or polymerase chain reaction-based tests. 

Management of influenza infection is mostly symptomatic and supportive. Medications for fever, sore throat, runny nose and cough, can alleviate discomfort but generally do not change the illness' course or recovery time. Adequate rest and fluid intake are important for recovery. Most children recover within one to two weeks without complications. 

Some high-risk children may benefit from antiviral drugs such as oseltamivir if administered early in the illness. These medications are most effective when started within the first two days of symptoms onset and may reduce severity and duration of symptoms. Their utility in otherwise healthy children is limited. The decision to use such medications will be made by the healthcare provider based on individual assessment.  

Ultimately, prevention is better than cure, and all children up to 6 years old, as well as the elderly, are advised to receive their annual influenza vaccinations. Vaccination reduces risk of influenza infection (but does not obviate it) and reduces the risk of severe illness. There are options of inactivated injected and live, intranasal vaccines available. Individuals should consult their healthcare provider about which option would be most suitable for them. 

In cases of flu-like symptoms, it is advisable to keep the child at home, minimise contact with others and consult a healthcare provider. The provider should determine the necessity of testing or treatment.  

Ensure the child drinks adequate fluids and passes urine at least every 6 hours. Appetite may be reduced when they are feeling unwell but will gradually return to normal as symptoms improve. 

When to seek emergency care

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