Dr. Hsu Han-lin shares about influenza A, influenza B, and children's health
On 5th June 2024, renowned paediatrician Dr Hui Hon-lam shared valuable knowledge about "Influenza A and B, children easily diagnosed" on RTHK's programme [Hong Kong Connect]. Since the winter flu season began in Hong Kong in early January, the level of flu activity has remained high, with 22 severe paediatric cases, including 3 deaths. What is the difference between Influenza A and B? Below is a portion of the programme's content:
Community spread of influenza A and B
The incidence of influenza affects between 10% and 15% of Hong Kong’s population. Each year, approximately 20% children and 5% adults are affected, of which 80% cases are caused by influenza A.The peak periods for influenza are January to March and June to August, with children under five and older people aged 65 and over being particularly at risk. In 2023, there were 274 severe cases and 174 deaths among adults, and two severe cases and two deaths among children.
Reasons for high mortality rates following childhood infection
Younger children are more severely affected due to their lower immunity. Elders are also more severely affected due to lower immunity and pre-existing conditions.
Transmission routes and incubation periods of influenza A and B
Transmission routes include droplets and secretions produced when an infected person coughs, sneezes or talks. The incubation period is about 1 to 4 days.
Symptoms and differences between Influenza A and Influenza B
The symptoms of influenza A and B are similar, mainly including fever, chills, lethargy, headache, cough, runny nose, sore throat, vomiting, and diarrhoea. Influenza has a more severe impact on young children and the elderly than on adults; children often have more severe fevers and more frequent nausea, vomiting, and diarrhoea.
Similarities between influenza A, influenza B, and coronavirus
Influenza A and B are similar to coronavirus infections, but influenza B tends to appear later in the season. Influenza B is typically less severe than influenza A, but there have been disproportionate deaths in children recently. Influenza A can spread from animals to humans and can cause pandemics, whereas influenza B can only spread between humans.
The importance of children receiving the flu vaccine
Of the 26 severe cases of influenza reported so far this year, 20 involved individuals who had not been vaccinated, highlighting the importance of vaccination in preventing influenza. The protection rate from an annual influenza vaccination is approximately 40% to 60%, and it can also reduce the risk of complications.Under the various vaccination programmes for the 2023/24 season, children and adolescents received over 530,000 doses of the influenza vaccine, with a vaccination rate of 53%. This represents an increase of approximately 37% compared with the same period last year and is a record high.
Methods for preventing and treating flu
In addition to vaccination, other methods to prevent children from contracting influenza include wearing masks in crowded places, frequent handwashing, and avoiding contact with individuals who have the flu. If a child is infected, they should get plenty of rest and drink more fluids, and should not attend school if symptoms appear. Antiviral drugs such as Tamiflu and Relenza can reduce the severity and duration of the illness, and antibiotics can be used to treat secondary bacterial infections in severe cases. If symptoms are severe, such as a young child having a high fever, severe cough with phlegm, shortness of breath, confusion, seizures, or low oxygen levels, hospitalisation is recommended.
Serious complications of influenza A and B
In young children, respiratory complications such as croup, bronchiolitis, and bronchitis may occur. Other complications in children include myocarditis, pericarditis, viral encephalitis, and meningitis. In people of all ages, dehydration can lead to the exacerbation of underlying chronic diseases, such as heart failure, myocardial infarction, cerebrovascular accident, diabetes, and chronic obstructive pulmonary disease. Both primary viral pneumonia and secondary invasive bacterial pneumonia can lead to acute lung injury, respiratory failure, septic shock, and multiple organ failure, which may subsequently lead to invasive infections such as meningococcal septicaemia and meningitis.
Source: RTHK Programme [Connecting Hong Kong] (5 June 2024)
