Context:

Delhi has witnessed a significant rise in flu cases over the past few weeks, with hospitals across the city reporting a spike in patients affected by Influenza B and H1N1 (swine flu) viruses. These strains of flu have affected all age groups, with symptoms like high-grade fever, cough, fatigue, and upper respiratory tract infections being commonly reported. Experts note that this year’s flu strain is particularly strong, leading to more severe cases.

About Influenza:

Influenza, commonly known as the flu, is an acute viral infection that primarily affects the respiratory tract. It is considered one of the most life-threatening infectious diseases worldwide.

The virus spreads through direct contact with infected individuals, contaminated objects, and inhalation of aerosolized virus particles. New strains of influenza can lead to global pandemics, as seen with avian flu in 1997 and swine flu in 2009.

Types of Influenza:

There are four main types of influenza viruses:

• Type A: Causes seasonal epidemics and is further classified into subtypes (e.g., A(H1N1) and A(H3N2)).
• Type B: Causes seasonal epidemics, but not classified into subtypes. It can be broken into two lineages: B/Yamagata and B/Victoria.
• Type C: Causes mild infections and is less common, with minimal public health importance.
• Type D: Primarily affects cattle and does not cause illness in humans.

Differences between influenza A and B

• Influenza A viruses can cause seasonal epidemics and pandemics. They are classified into subtypes (A(H1N1), A(H3N2)), based on protein combinations on their surface.
• Influenza B viruses are also responsible for seasonal epidemics but are not classified into subtypes. Instead, they are divided into two lineages: B/Yamagata and B/Victoria.

What is the difference between A(H1N1) and A(H3N2)?
Both are subtypes of influenza A viruses that circulate in humans.

• A(H1N1): This virus caused the 2009 pandemic and replaced the previous A(H1N1) strain. It is also known as A(H1N1)pdm09.
• A(H3N2): This is another common subtype of influenza A that is often associated with severe flu seasons.

Seasonal influenza affects nearly a billion people each year, with 3–5 million cases resulting in severe illness. It is responsible for an estimated 290,000 to 650,000 respiratory deaths annually. Tragically, 99% of deaths among children under 5 years old, who suffer from influenza-related lower respiratory tract infections, occur in developing countries.

Conclusion:

Seasonal influenza like as in Delhi is a common illness that can lead to severe health complications, especially in vulnerable groups. Vaccination and good hygiene practices are the best ways to prevent influenza and reduce its spread. If symptoms appear, early treatment can help manage the illness and reduce the risk of severe outcomes.