Influenza A (H3N2) Variant Virus -An Overview

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Influenza virus can spread from pigs to humans and from humans to pigs. The spread from pigs to humans can occur in the same way the transmission of the virus occurs between people.

During the year 2009, the H1N1 virus was circulating with the M gene and was first detected in pigs during the year 2010. The H3N2 variant virus was first detected in humans in 2011 with the same M gene.

According to WHO (World Health Organisation), the acquisition of the M genes during the year 2009 made the virus infect humans easily.

Causes of H3N2

Influenza virus can spread from pigs to humans and from humans to pigs. The spread from pigs to humans can occur the same way the transmission of the virus occurs between people.

The transmission occurs mainly through the droplet of infected pigs when the pig coughs and sneezes. When the infected droplets come in contact with your nose or mouth, or you tend to inhale them, you can get infected with the flu.

WHO also states that when you tend to touch something that the virus contains and then touch your mouth or nose, you can get infected.

The third possible way to get infected with the virus is through inhalation of the particles that the virus contains. However, scientists are figuring out the possible and frequent ways the virus infects humans.

Symptoms of H3N2

The symptoms of the H3N2 variant virus are similar to the seasonal flu. Some of the common symptoms include

Diagnosis of H3N2

The H3N2 variant virus symptoms will be similar to the common cold and other seasonal flu. So early diagnosis is crucial to differentiate between the seasonal flu and the variant virus.

CDC states that the diagnosis of influenza is not necessary for all people, even if they exhibit the symptoms. The diagnosis can be useful and yield clinically useful results when there is an outbreak in a closed setting, for example, in hospitals, boarding schools, summer camps and long-term facilities.

Testing in such camps can help in determining whether the influenza virus is the cause of the outbreak. Some of the common diagnostic methods for influenza viruses are

  • Immunofluorescence assay
  • Rapid molecular assay
  • Viral culture
  • Reverse transcription polymerase chain reaction (RT-PCR)
  • Serology
  • Rapid antigen testing

The sensitivity and specificity of the test will depend on the handling techniques of the laboratory. The collected samples will also have an impact on the result. The sample collection should be done within the first 3-4 days of illnesses.

Rapid influenza diagnostic tests (RIDTs) will provide the result in approximately 1in 15 minutes. Results for viral cultures will take about 3-10 days. Rapid molecular testing can provide the results within 20 minutes with high specificity and sensitivity.

Treatment of H3N2

The H3N2 variant virus can be treated with the same medications and drugs that are used to treat influenza. The Centre for Disease Control (CDC) suggests the list of these drugs.  

  • Oseltamivir
  • Peramivir
  • Zanamivir
  • Baloxavir

Apart from medications, follow these simple steps during your recovery phase and manage your symptoms.

  • Drink only boiled water.
  • Consume foods that are rich in vitamin C.
  • Drink warm water to ease sore throat and nasal congestion.

Early diagnosis and treatment are important, especially for people with weakened immunity.

Risk factors of flu

According to CDC, people with the following traits are at a higher risk of getting affected by the flu.

  • People aged 65 and above.
  • Asthma patients.
  • People affected with Neurological and neurodevelopmental conditions.
  • Children younger than two years old.
  • Blood disorders like sickle cell disease.
  • Chronic lung diseases like cystic fibrosis and chronic obstructive pulmonary disease (COPD).
  • Endocrine disorders like diabetes mellitus.
  • Heart diseases like coronary artery disease, congenital heart disease and congestive heart failure.
  • Kidney diseases
  • Liver disorders
  • Metabolic disorders like mitochondrial disorders and inherited metabolic disorders.
  • People obese with a body mass index [BMI] of 40 or higher.
  • People younger than 19 years old on long-term aspirin- or salicylate-containing medications.
  • People with weakened immunity due to diseases affected like HIV or AIDS or some cancers such as leukaemia or medications like those receiving chemotherapy or radiation treatment for cancer, or people with chronic conditions requiring chronic corticosteroids or other drugs that suppress the immune system.
  • People who have had a stroke.

Other people at a higher risk of getting infected with the flu are

  • Pregnant women and women up to 2 weeks after the end of pregnancy.
  • People who live in nursing homes and long-term care facilities.
  • All children under five years old are considered at a higher risk of flu complications. The highest risk is for those infants younger than two years old, with the highest hospitalization and death rates among infants younger than six months old.

Vaccine for H3N2

Currently, scientists are working to produce a vaccine against the virus. However, a pilot vaccine was produced for the H3N2 variant virus. Other vaccines are currently in the preclinical study phase. The development of new vaccines also indicates that effective vaccines can be developed, and significant immune responses can be created with the help of vaccines.

Preventing H3N2

The H3N2 variant virus is a seasonal flu and can be prevented with certain precautionary steps.

  • Vaccines are the best way to prevent getting infected with the virus. So, try to get vaccinated.
  • Wash hands frequently with soap and water. Do not touch your nose, mouth and face with dirty hands.
  • Before and after using a public washroom, flush it and then use it. After using the washroom, wash your hands with soap and water.
  • Avoid crowded areas like malls, theatres, beaches and office buildings. These can be the primary contact of flu transmission.
  • Avoid contact with sick people.
  • If you are sick, avoid travelling and stay home for at least 24 hours. When your fever has gone down, you can travel. However, try to wear a mask when you travel.
  • Do not consume food and drink water near the pig barns.
  • Avoid contact with pigs that look ill.
  • If you come in contact with pigs, try to take some protective measures.
  • If your fever does not subside within two days.


The H3N2 variant virus is a seasonal flu and can be controlled with vaccination. If you think there is an outbreak in your work environment or the school your kids are studying, try to stay at home. Additionally, early diagnosis is crucial in controlling the spread.

Treatment for the H3N2 variant virus can be done using the available antiviral drugs. Additionally, antibiotics should not be overused as they can lead to drug-resistant variants, which can be difficult to treat in future.

If your symptoms are similar to common colds and the symptoms do not settle after three days, consult your doctor.


Is H3N2 the swine flu?

The H3N2 is a variant virus of swine flu. The virus was initially found in pigs and then got transformed into humans.

How long does H3N2 flu last?

The flu symptoms can last for about 4-7 days. During this period, you can be contagious, so always wear a mask when going out. Try to stay home during the infectious period to avoid transmission.

How is H3N2 transmitted?

The H3N2 virus can get transmitted through droplets when sneezing, coughing or by close contact. When these droplets reach your nose, mouth and face, you can get infected with the virus.


The Information including but not limited to text, graphics, images and other material contained on this blog are intended for education and awareness only. No material on this blog is intended to be a substitute for professional medical help including diagnosis or treatment. It is always advisable to consult medical professional before relying on the content. Neither the Author nor Star Health and Allied Insurance Co. Ltd accepts any responsibility for any potential risk to any visitor/reader.

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