Does the H1N1 Virus Still Exist?

The H1N1 virus—known as swine flu—is one type of influenza A virus. Influenza A(H1N1) viruses still exist today.

Scientists call it the A (H1N1)pdm09 virus. Influenza type A and type B viruses cause disease epidemics in people during flu season. During most years, this is the winter months.

The H1N1 virus emerged during the 2009–2010 flu season, when it caused a pandemic. It is often called swine flu because it is a combination of influenza viruses that infect pigs, birds, and humans. Today, it is one of the strains that causes seasonal flu.

The H1N1 virus causes common flu symptoms in most people. Those who are pregnant, have a chronic health problem, or have a weakened immune system have a higher risk of severe effects from this virus.

This article describes H1N1 virus history, causes, and risks.

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What Was the Swine Flu Pandemic in 2009?

The swine flu pandemic in 2009 was a global outbreak of the influenza A(H1N1) pdm09 virus. It was a strain of influenza viruses never before identified as a cause of infections in humans. The virus originated from animal influenza viruses that typically attack swine.

The first reports of the swine flu occurred in a 10-year-old patient in California in April 2009. An 8-year-old patient was infected with the same novel virus in an adjacent California county a few days later. The virus spread quickly around the world. The World Health Organization (WHO) declared the H1N1 pandemic in June 2009, affecting people worldwide.

The H1N1 virus that caused the swine flu pandemic in 2009 was very different from other H1N1 viruses existing at the time. Few young people had been able to build up an antibody response to this new virus before being infected. However, people older than age 60 had antibodies to protect them from the virus, likely from exposure to earlier H1N1 viruses earlier in their lives. As a result, the virus primarily affected children and young and middle-aged adults.

An H1N1 vaccine was produced and available in large quantities in late November 2009. However, this was after the peak of illness during the second wave of flu infections had come and gone in the United States. WHO declared an end to the pandemic on August 10, 2010.

Impact of the 2009 Swine Flu Pandemic

Statistics from the CDC, below, reflect the impact of the swine flu from April 12, 2009, to April 10, 2010, during the H1N1 pandemic in the United States:

  • 60.8 million cases
  • 274,304 hospitalizations
  • 12,469 deaths

The CDC estimated that 151,700 to 575,400 people died from the 2009 H1N1 viral infection during the first year that the virus circulated. The majority of these deaths occurred in Southeast Asia and Africa, where there was likely limited access to disease prevention and treatment.

Does the H1N1 Virus Still Exist?

Influenza A(H1N1) viruses still exist today, though it is considered under control. It is related to the H1N1 virus that caused a flu pandemic in 2009-2010.

H1N1 continues to exist as a seasonal flu virus, causing illness, hospitalization, and deaths worldwide. The seasonal flu vaccine has included a component that protects against H1N1 every year since 2010.

How Does H1N1 Spread?

H1N1 is caused when the virus infects the mucous membranes that line your nose, throat, or lungs. This can occur from breathing in an infected person's droplets when they cough, sneeze, breathe, or talk. It can also occur when you transfer the virus to your eyes, nose, or mouth by touching an infected surface and then touching these areas of your body.

The swine flu incubation period (the amount of time it takes for the infection to develop after you have been exposed to H1N1) is up to seven days. An infected person can likely spread the virus from about a day before developing symptoms until about seven days after symptoms begin. If you have a weakened immune system, you may be able to spread the virus for a slightly longer time.

How Contagious Is H1N1?

H1N1 is a very contagious respiratory disease. It can spread from person to person, by direct contact with infected saliva or mucus secretions, or by contact with infected inanimate objects such as desks or utensils.

H1N1 is now part of the seasonal flu. The spread involves one of the following circumstances:

  • Transmission from person to person occurs through exposure to coughing and/or sneezing of people infected with the H1N1 virus and the virus enters one of your mucous surfaces in your eyes, nose, or mouth.
  • Infection with the virus occurs by touching something with the flu virus on it, then using the same hand to touch your mouth or nose.
  • Rarely, human infection from pigs occurs when an infected pig coughs or sneezes and droplets with the flu virus spread through the air and are inhaled by a person, usually farmers and other humans who work with pigs.

While the swine flu is related to a virus that affects pigs, you can't catch swine flu from eating pork.

Who Can Get H1N1 Today?

Anyone can get H1N1 today. However, people who have underlying medical conditions and/or compromised immune systems are more likely to get the most severe illness.

The following groups have the highest risk of getting the swine flu and becoming the sickest from it:

  • Pregnant women
  • Children and young adults between 6 months and 24 years of age
  • People of any age with certain chronic medical conditions like asthma, diabetes, or lung disease
  • People under 19 years who are receiving long-term aspirin therapy
  • Adults age 65 years or older
  • Residents of nursing homes and other chronic care facilities
  • People of any age with weakened immune systems due to circumstances such as cancer treatments, organ transplants, or long-term use of steroids
  • Obese people, categorized as those with a body mass index (BMI) of 40 or higher

When to See a Healthcare Provider

If you are in general good health and become infected with H1N1, you may not need to see a healthcare provider. Most people who become infected with swine flu can endure symptoms of H1N1 and recover without complications.

People who are pregnant, immunocompromised, or have a chronic disease, and others who have a high risk of complications from the flu should contact a healthcare provider when flu symptoms develop.

Get immediate medical care if you have swine flu and develop any of the following emergency symptoms:

An emergency in symptoms for children with the flu is slightly different from those that affect adults. Get immediate medical if your child develops any of the following symptoms while they have the flu:

  • Working hard to breathe or breathing fast
  • Dehydration (dry mouth, tearless crying, or lack of urination for eight hours)
  • Pale, gray, or blue-colored skin, lips, or nail beds depending on skin color
  • Ribs pulling in with each breath
  • Pain or pressure in the chest or abdomen
  • Confusion
  • Seizures
  • Severe or persistent vomiting
  • Severe muscle pain or refusal to walk
  • Fever above 104 degrees F that is not controlled by fever-reducing medicine
  • Fever or cough that improves but then returns or worsens
  • Any fever in children younger than 12 weeks
  • Worsening of existing medical conditions


The H1N1 virus is a type of influenza A virus. It is also called swine flu because it formed from the virus that affects pigs before it became H1N1 and infected humans.

This virus causes common flu symptoms in most people. Like other types of flu, you have a higher risk of severe symptoms if you have a chronic condition, a weakened immune system, or are pregnant.

While the H1N1 virus still exists today, it is under control. The annual vaccine protects against the H1N1 virus and other strains of the flu most common for the flu season it is given.

10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Beacon Health System. H1N1 flu (swine flu).

  2. Centers for Disease Control and Prevention (CDC). The 2009 H1N1 pandemic: summary highlights, April 2009-April 2010.

  3. Centers for Disease Control and Prevention (CDC). 2009 H1N1 Pandemic.

  4. American Academy of Family Physicians. H1N1 influenza.

  5. Centers for Disease Control and Prevention (CDC). H1N1 flu.

  6. Mount Sinai. H1N1 influenza (swine flu).

  7. Centers for Disease Control and Prevention (CDC). Key facts about human infections with variant viruses.

  8. Association for Professionals in Infection Control and Epidemiology. H1N1 flu (swine flu).

  9. New York State Department of Health. H1N1 flu and seasonal flu: differences and similarities.

  10. Centers for Disease Control and Prevention. Flu symptoms & complications.

Anna Zernone Giorgi

By Anna Giorgi
Giorgi is a freelance writer with more than 25 years of experience writing health and wellness-related content.