Understanding the flu landscape in Hong Kong
Health authorities warn that the current flu season in Hong Kong could stretch into November, underscoring the importance of vaccination and personal protection. While influenza type A and type B can both lead to serious illness, they behave differently in terms of spread, severity, and affected groups. For residents navigating a peak season with evolving strains, a clear picture of the two main influenza families helps residents take informed precautions.
What is influenza A and how does it differ from influenza B?
Both influenza A and B can cause severe respiratory illness, but they differ in their patterns and population impact. Influenza A is known for its ability to rapidly mutate, producing new subtypes that can lead to larger outbreaks. In Hong Kong, the H3 subtype of influenza A is currently the most common, responsible for roughly 60% of local infections, followed by the H1 subtype at about 35%. The remaining 5% are influenza B infections, according to health authorities.
Influenza B tends to be less common than influenza A and often causes milder illness on average. However, it can be more severe in certain groups—particularly children and the elderly. Dr Leung Chi-chiu, a respiratory medicine specialist, notes that the lack of major influenza B circulation since the Covid-19 pandemic means herd immunity remains relatively low, especially among children who may not have been exposed to B strains since birth. This creates a window of vulnerability even for those who usually fare well during typical flu seasons.
Public health messaging emphasizes that both influenza A and B can lead to complications requiring medical care. In practice, this means that vaccination and prompt symptom monitoring are essential year after year, regardless of the predominant strain.
Why does the current mix of strains matter for you?
The composition of circulating strains influences vaccine effectiveness and how health authorities tailor public health guidance. With H3 accounting for a large share of infections, vaccines that target the common A strains remain a cornerstone of protection for the community. People most at risk of severe disease—older adults, young children, pregnant individuals, and those with chronic health conditions—should prioritize vaccination and early treatment if symptoms appear.
Practical protection tips for the public
- Get vaccinated. Flu vaccines are updated annually to cover the most prevalent strains, including A/H3 and A/H1 subtypes as well as B lineages. Vaccination reduces the risk of severe illness and hospitalisation.
- Wash hands and adopt good hygiene. Regular handwashing with soap, using alcohol-based sanitizers, and avoiding touching the face help limit transmission in crowded urban settings like Hong Kong.
- Avoid close contact when sick. If you or a household member shows flu-like symptoms, minimising contact reduces spread to others, especially vulnerable individuals.
- Mask in crowded places during peak season. Masks can lower the risk of respiratory virus transmission in transit hubs, markets, and busy workplaces.
- Seek timely medical care. If you experience high fever, persistent cough, shortness of breath, or chest pain, contact health services promptly, especially if you’re in a high-risk group.
- Stay hydrated and rest. Adequate fluids and rest support the body’s ability to fight infection and recover quicker.
What residents should watch for and when to seek help
Common flu symptoms—fever, cough, body aches, and fatigue—can overlap with other respiratory illnesses. Because influenza A (notably H3) and B are circulating, monitoring symptom onset and severity is crucial. Health officials encourage vaccination as the most effective preventive measure, paired with personal hygiene practices and sensible public health choices in crowded settings.
Bottom line
In Hong Kong’s current flu landscape, influenza A, particularly the H3 subtype, remains the leading cause of local infections, while influenza B accounts for a smaller share but poses significant risk to children and the elderly. Vaccination, good hygiene, and prudent health decisions are essential to protect yourself and your loved ones during this ongoing flu season.
