From Delhi to Bengaluru and Gujarat, H1N1 influenza cases are rising across India, putting seasonal flu back in the spotlight. Delhi had recorded 1,449 H1N1 cases by August 12, more than six times the 229 cases reported during the corresponding period in 2025, according to National Centre for Disease Control (NCDC) data. More recent reports put Delhi's tally at 1,777 cases this year. Karnataka has also crossed 4,000 H1N1 cases this year, with Bengaluru accounting for more than half of the state's reported infections. Currently, there are 300 to 400 active cases of H1N1 in Bengaluru. Health authorities have, however, stressed that the rise does not necessarily mean a new or unusually dangerous virus is circulating.

Against this backdrop, one familiar term is making a comeback: "swine flu". But doctors say that name is technically outdated when referring to the H1N1 virus currently circulating among humans.

So, if hospitals and health departments are reporting H1N1 cases, why do people still call it swine flu? Is it actually linked to pigs? And does the change in terminology mean the infection is less serious?

Doctors explain what the name really means, and why it matters as H1N1 cases rise.

H1N1 Cases Are Rising, But This Is Not A New "Swine Flu" Virus

The current increase in cases does not mean that a new swine-origin virus has suddenly emerged in India. The virus responsible for the 2009 pandemic is formally known as influenza A(H1N1)pdm09. After the 2009 pandemic, it became established as a seasonal human influenza virus and has continued to circulate alongside other influenza viruses, particularly A(H3N2).

The World Health Organization (WHO) says A(H1N1)pdm09 is now a seasonal human influenza virus and specifically notes that the term "swine flu" is misleading when used for human seasonal influenza.

Dr Niraj Kumar, Senior Consultant, Internal Medicine, ShardaCare-Healthcity, says, "The term 'swine flu' is largely a historical and media term and is no longer considered the medically accurate name for the H1N1 virus circulating among humans."

He explains that the virus responsible for the 2009 pandemic is formally known as influenza A(H1N1)pdm09 and is now considered a seasonal human influenza virus. This is particularly relevant now because a rise in H1N1 cases in several Indian states can easily create the impression that the country is experiencing a repeat of the 2009 pandemic.

It isn't. WHO declared the 2009 H1N1 pandemic over in August 2010, after which the virus continued circulating as seasonal influenza. WHO subsequently standardised the terminology A(H1N1)pdm09 to distinguish it from older H1N1 viruses that had circulated in humans before 2009. 

Also Read: The Pandemic Before Covid: The 2009 Swine Flu Surge And Its Impact On Current Disease Response

Why Was H1N1 Ever Called Swine Flu?

The term originated during the 2009 pandemic because genetic analysis showed that the newly identified virus contained gene segments related to influenza viruses found in pigs.

But "swine flu" gave the public a much simpler, and potentially misleading, picture of what was happening.

The pandemic virus acquired the ability to spread efficiently from person to person. Once it became established among humans, direct contact with pigs was no longer necessary for its transmission.

Dr Kumar explains that the virus "was not simply a pig virus being continuously transmitted from pigs to humans." Instead, people infected with seasonal H1N1 generally acquire it from other infected people through respiratory droplets and aerosols. WHO's South-East Asia regional guidance makes the distinction particularly clearly: A(H1N1)pdm09 is technically not "swine flu" when it is circulating among humans because it is efficient at human-to-human transmission without direct involvement of pigs.

Can You Get H1N1 From Pork Or Pigs?

This is one of the biggest misconceptions created by the term "swine flu". Eating properly handled and cooked pork does not cause seasonal H1N1 influenza.

Dr Aishwarya R, Consultant - Infectious Diseases, Aster Whitefield Hospitals, Bengaluru, says, "The problem with using the term 'swine flu' is that it might mislead one into thinking that the disease is contracted through consuming pork or interacting directly with pigs." She adds that seasonal H1N1 is transmitted "person to person through respiratory droplets and close interaction, just like any other form of influenza."

That distinction is important because swine influenza viruses do exist. Influenza viruses circulate in pig populations, and occasional infections in humans can occur after exposure to infected animals or contaminated environments. But those infections are not automatically the same thing as the established human seasonal A(H1N1)pdm09 virus. WHO therefore distinguishes between human seasonal influenza A(H1N1)pdm09 and influenza viruses that circulate primarily among pigs.

What Does H1N1 Stand For?

The name H1N1 actually tells us something about the virus.

Influenza A viruses are classified according to two surface proteins:

  • H = haemagglutinin
  • N = neuraminidase

Different combinations of these proteins produce different influenza A subtypes, including H1N1 and H3N2.

Dr Aishwarya explains that these proteins help identify the subtypes of influenza A. WHO currently identifies A(H1N1) and A(H3N2) as the influenza A subtypes circulating among humans. The H1N1 virus associated with the 2009 pandemic is written as A(H1N1)pdm09. 

The "pdm09" therefore isn't a new strain appearing in 2026. It refers to the pandemic-origin virus from 2009.

Why Are Doctors Using H1N1 During The Current Surge?

Because H1N1 is still circulating. The current cases in Delhi, Bengaluru and other parts of India are part of the continuing circulation of seasonal influenza rather than evidence that the 2009 pandemic virus has suddenly returned.

WHO's influenza surveillance data and vaccine recommendations continue to include A(H1N1)pdm09 as one of the seasonal influenza viruses monitored globally. The virus is also included in the recommended composition of influenza vaccines for the 2026-27 Northern Hemisphere season.

Recent WHO surveillance documents have also recorded A(H1N1)pdm09 circulation in India and other parts of the world. So while the number of cases may rise, the name of the virus does not revert to "swine flu".

Does The Name Change Mean H1N1 Is Less Dangerous?

No. Calling it H1N1 influenza rather than swine flu does not mean the infection is harmless. Seasonal influenza can range from mild illness to severe respiratory disease, pneumonia, hospitalisation and death. WHO estimates that seasonal influenza causes around 3-5 million cases of severe illness and 290,000-650,000 respiratory deaths globally every year.

Older adults, young children, pregnant women and people with chronic medical conditions or weakened immunity are at greater risk of complications.

Dr Kumar says H1N1 "has not disappeared" and remains one of the influenza A viruses circulating seasonally in humans alongside H3N2. The current rise in cases therefore deserves attention, but not necessarily panic.

The Indian health system has continued to maintain surveillance for seasonal influenza. NCDC's influenza programme includes surveillance, laboratory testing, clinical guidance and public-health advisories for seasonal H1N1. 

Why Is The Term "Swine Flu" Medically Problematic?

There is a scientific reason, and a social one. WHO's best-practice guidance for naming infectious diseases recommends avoiding names based on geographical locations, animals, foods, communities or occupations because they can create stigma and unintended social and economic consequences. "Swine flu" is specifically listed among the examples of animal- or food-based disease names to avoid.

That concern became particularly visible during the 2009 pandemic, when the term "swine flu" created fears around pork consumption and affected the pig industry.

Dr Aishwarya says, "Another reason for the change in terminology is that naming the disease in terms of animal or geography or community might lead to stigmatization." Using H1N1 influenza instead keeps the terminology focused on the actual virus and its subtype rather than its historical association with animals.

Also Read: Antivirals, Not Antibiotics, Work For H1N1: How Oseltamivir Treats Influenza Viruses

H1N1 Symptoms: What To Watch For

The symptoms of H1N1 are broadly similar to those caused by other seasonal influenza viruses.

They can include:

  • Fever
  • Cough, often dry
  • Sore throat
  • Runny or blocked nose
  • Headache
  • Muscle or body aches
  • Fatigue
  • Chills

Most people recover without serious complications. However, difficulty breathing, persistent or worsening symptoms, chest pain, confusion, severe weakness or deterioration in someone belonging to a high-risk group should prompt medical assessment. WHO notes that influenza can cause severe disease, particularly in people at higher risk.

And with H1N1 activity currently rising in multiple parts of India, doctors advise against dismissing persistent flu-like symptoms or relying solely on self-medication.

What Should You Call It: H1N1 Or Swine Flu?

People are likely to continue saying "swine flu", the term has been embedded in public conversation since 2009. But in medical and public-health communication, H1N1 influenza, influenza A(H1N1) or A(H1N1)pdm09 is more accurate.

As Dr Aishwarya puts it, "In a healthcare setting, the correct term would be influenza A(H1N1) or simply H1N1 influenza, which is more scientific and less confusing."

That distinction becomes especially useful now, when rising H1N1 numbers across Indian cities could otherwise be interpreted as a return of the 2009 pandemic. So, no, the current H1N1 surge does not mean people are suddenly catching a new virus from pigs.

But it does mean influenza deserves to be taken seriously, particularly by people at higher risk of complications. The important question is therefore not whether you call it "swine flu" or H1N1, but whether you recognise the symptoms, prevent transmission and seek medical care when influenza becomes severe.



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