Delhi has reported 1,777 cases of H1N1 influenza so far this year, including 114 new cases recorded on August 20, according to the latest Delhi government data. In all, the national capital has recorded 2,602 seasonal influenza cases in 2026, comprising 2,392 Influenza A cases and 210 Influenza B cases. H1N1 accounts for the largest share of the Influenza A infections, making it the predominant influenza subtype reported in Delhi this year. 

The rise in cases has prompted concerns about whether a new or more dangerous H1N1 variant could be circulating in the capital. However, senior scientists at the Indian Council of Medical Research (ICMR) have clarified that no new H1N1 strain has been detected in India and said there is no cause for panic.

According to ICMR scientists, the Influenza A(H1N1)pdm09 viruses currently circulating in the country belong to the A/Missouri/11/2025 (H1N1)pdm09-like virus strain. The viruses belong to clade 6B.1A.5a2a and subclade D.3.1.1, and have been in circulation since 2025. The scientists stressed that the current rise therefore does not represent the emergence of a new H1N1 strain. 

ICMR has also said that the influenza viruses currently circulating are well matched with the vaccine strains recommended for the Northern Hemisphere. Seasonal influenza, including H1N1, is generally self-limiting, although young children, older adults and people with underlying medical conditions can be at greater risk of complications. 

Dos

• Cover your mouth and nose with a handkerchief or tissue when you cough or sneeze.
• Wash your hands often with soap and water.
• Stay away from public places if you have fever, coughing and sneezing.
• Drink plenty of water and eat nutritious food.
• Sleep well and stay rested.

Don’ts

• Shake hands or use other contact greetings.
• Spit in public.
• Take medicines without consulting the physician.

 

Against this backdrop, while the current rise in cases does not indicate a new H1N1 strain, preventing infection and limiting its spread remain important. Here is what you need to know about H1N1, its symptoms and transmission, and the dos and don’ts advised by health authorities.

What is H1N1 flu (swine flu)?

According to the Mayo Clinic, H1N1 flu, sometimes called swine flu, is a type of Influenza A virus. During the 2009–10 flu season, a new H1N1 virus began causing illness in humans. It was commonly called swine flu and represented a new combination of influenza viruses that infect pigs, birds and humans. 

The World Health Organization declared H1N1 a pandemic in 2009. Mayo Clinic notes that the virus caused an estimated 284,400 deaths worldwide that year. WHO declared the pandemic over in August 2010, but the H1N1 strain responsible for the pandemic subsequently became one of the strains that cause seasonal influenza. 

Swine flu (H1N1) can show up through symptoms such as fever, cough, sore throat, headache, runny nose, body aches and fatigue.

Recognise the signs early and don’t ignore persistent symptoms. If you experience these symptoms, seek medical advice at your nearest healthcare centre.… pic.twitter.com/9ephVereZ5

— Ministry of Health (@MoHFW_INDIA) August 22, 2026

As Mayo Clinic explains, “The H1N1 flu, sometimes called swine flu, is a type of influenza A virus.” It also notes that most people with influenza recover on their own, although flu and its complications can be serious or even fatal, particularly among people at higher risk. Seasonal influenza vaccination can help protect against H1N1 as well as other seasonal influenza viruses. 

H1N1 should not be confused with a separate disease that people can contract by eating pork. The virus spreads primarily from person to person, and eating properly handled and cooked pork does not cause H1N1 infection. 

What causes H1N1, is it contagious and what are the symptoms?

H1N1 is caused by an Influenza A virus and is contagious. According to Mayo Clinic, influenza viruses such as H1N1 infect cells lining the nose, throat and lungs. The virus can spread through respiratory droplets released when an infected person coughs, sneezes, breathes or talks. A person can also become infected by touching a contaminated surface and then touching their eyes, nose or mouth. 

People infected with influenza may be able to spread the virus from around one day before symptoms appear until about four days after symptoms begin, while children and people with weakened immune systems may remain infectious for longer. 

H1N1 symptoms are similar to those caused by other influenza viruses and can develop relatively quickly. Mayo Clinic lists fever, aching muscles, chills and sweating, cough, sore throat, runny or stuffy nose, watery or red eyes, eye pain, body aches, headache, tiredness and weakness among possible symptoms. Diarrhoea and nausea or vomiting can also occur, with vomiting more commonly seen in children than adults. Symptoms generally develop one to four days after exposure. 

Swine flu (H1N1) can spread from person to person, but simple precautions can help protect you and those around you.

Stay alert to symptoms, practise good hygiene and avoid self-medication. If you experience symptoms, seek medical advice at your nearest healthcare centre.… pic.twitter.com/PX13vu2iRD

— Ministry of Health (@MoHFW_INDIA) August 20, 2026

Not everyone with H1N1 will develop the same combination or severity of symptoms. Most otherwise healthy people recover without major complications. However, some groups have a higher risk of severe influenza, including young children, older adults, pregnant people, individuals with weakened immune systems and those with chronic conditions such as asthma, diabetes and heart disease. 

Influenza can sometimes lead to complications such as pneumonia, bronchitis, respiratory failure, worsening of existing heart or lung conditions, neurological complications and secondary bacterial infections. 

People with flu-like symptoms who are pregnant or have a chronic illness should contact a healthcare provider. Emergency medical attention is particularly important if symptoms include difficulty breathing or shortness of breath, chest pain, signs of dehydration such as not urinating, persistent dizziness, seizures, severe weakness or worsening of an existing medical condition. In children, difficulty breathing, chest pain, dehydration, seizures, severe muscle pain or worsening of an existing condition are warning signs requiring urgent medical care. 

What are the dos and don’ts advised by the government?

As H1N1 spreads from person to person, basic respiratory and hand hygiene can help reduce transmission. The Ministry of Health lists several measures that people should follow when dealing with seasonal influenza and H1N1.

Also read: Flu vaccines don’t work? Experts push back hard on Dr Oz’s viral remarks