Flu Cases Rising in India

What’s in today’s article?

• Why in news?
• H3N2 Virus
• What is the H3N2 Virus? 
• Is H3N2 a new sub-type of influenza?
• News Summary: Flu cases rising in India
• Why is there an increase in flu cases?
• Have Covid-19 cases spiked as well?
• Is it unusual for people to die of the flu?
• Why is the flu shot updated every year?

Why in news?

• The Centre last week reviewed the rise in cases of influenza, and states have been readying hospitals for a possible spike in infections. 
• The Union Health Ministry has confirmed a death each in Haryana and Karnataka due to the H3N2 subtype of the flu virus this month.

H3N2 Virus

What is the H3N2 Virus? 

• Influenza viruses, which cause the infectious disease known as flu, are of four different types: A, B, C and D. 
• Influenza A is further classified into different subtypes and one of them is the H3N2. 

Image Caption: H3N2 Influenza 

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Is H3N2 a new sub-type of influenza?

• No, it is one of the sub-types of the influenza virus that has been known to cause seasonal infections. In fact, H3N2 caused a flu pandemic back in 1968.
• In India, this sub-type was detected in 1996 and has since caused outbreaks too. 
• The only difference this year is that the disease seems to be a little more severe than we would usually see with H3N2.

News Summary: Flu cases rising in India

Why is there an increase in flu cases?

• Flu season
  • Officials and experts said the current spike is because, first, this is the flu season. 
  • India usually sees two flu peaks every year — between January and March and, post-monsoon, between August and October. 
    • The virus spreads as the season changes.
• Lower immunity
  • Fewer flu infections during the pandemic has resulted in a large reservoir of people with lower immunity.
    • The two pandemic years, 2020 and 2021, reported only 2,752 and 778 cases of the flu respectively.
  • Every year there is a subclinical spread of influenza and people acquire some immunity to it. 
  • But during the pandemic, people masked up, stayed away from crowded areas, avoided gatherings, and this spread could not occur. Hence, there is an increase this year.
• Changing nature of flu virus
  • The flu virus is prone to changing its structure. This means that we see an increase in flu cases usually every other year.
• Availability of flu shot
  • India’s burden of conditions like diabetes and heart disease — which are risk factors for severe disease — is huge even among the young. 
  • The yearly flu shot is not readily available in government set-ups, and its uptake is not high.

Have Covid-19 cases spiked as well?

• At least two states, Gujarat and Maharashtra, have reported a new sub-variant of the novel coronavirus, XBB.1.16. 
• However, very few genome sequences are available, and not much is known about the sub-variant yet.
• Researchers have said that although there seems to be a growth advantage — seeing as it is replacing previously dominant variants — whether it could lead to a surge or to severe cases is not known. 
• Hospitals are still reporting Covid-19 cases with upper respiratory tract symptoms and fever, similar to what is seen with the flu.
• The Centre has written to six states — Tamil Nadu, Telangana, Kerala, Karnataka, Gujarat, and Maharashtra — asking them to carry out: 
  • adequate and proactive testing, 
  • monitor new and emerging clusters of infections, 
  • keep an eye on influenza like illnesses (ILI) coming to health facilities, and 
  • send samples of international travellers, sentinel sites, and clusters for genomic sequencing.

Is it unusual for people to die of the flu?

• Flu causes mild symptoms like fever, cough, and runny nose in most people.
• However, like Covid, it can lead to complications like pneumonia and acute respiratory distress syndrome (ARDS) that can lead to death.
• Very young children, old people, people with comorbidities such as heart disease, diabetes, and kidney disease, pregnant women, and those with a weakened immune system are at higher risk of getting severe disease.

Why is the flu shot updated every year?

• The flu vaccine usually contains four subtypes — two each of influenza A (H1N1 and H3N2 are recommended for 2022-23) and influenza B.
• The list of subtypes to be included in the yearly flu shot is updated by the World Health Organisation twice a year depending on the types in circulation.
• The ICMR network of viral laboratories test respiratory samples throughout the year to continuously update the vaccine.
  • This is because of the constantly evolving nature of influenza viruses.
  • It can undergo an “antigenic drift” to acquire mutations that change the part that cause the body to elicit an immune response.
  • It can also undergo an “antigenic shift” — an abrupt, major change that leads to a new protein structure of the virus.
    • These shifts can lead to pandemics such as the one in 2009, or even the Spanish flu of 1918.

Q1) What is flu?

Influenza, commonly known as “the flu,” is a contagious respiratory illness caused by the influenza virus. It can cause a range of symptoms, from mild to severe, including fever, cough, sore throat, body aches, fatigue, and sometimes vomiting and diarrhea.

Q2) What is Covid-19?

COVID-19 (Coronavirus Disease 2019) is an infectious respiratory illness caused by the SARS-CoV-2 virus. It was first identified in Wuhan, China in December 2019 and has since become a global pandemic, affecting millions of people worldwide.

Source: Flu cases rising in India, what is driving the surge? | Indian Express